Effects of Exotic Species Introductions on Fish / Perch Populations

Dr. John Janssen, Loyola University, Chicago, Illinois

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

David Clapp, Michigan Department of Natural Resources, Charlevoix, Michigan

Trends in Salmon Populations

Brad Eggold, Wisconsin Department of Natural Resources, Plymouth, Wisconsin

GREAT LAKES FISHERIES DECLINE

LIGHTLY EDITED, VERBATIM TRANSCRIPT

[We apologize for any errors in this lightly edited, verbatim transcript.]

Fred Binkowski, WATER Institute, Milwaukee, Wisconsin

Good morning. We would like to get started here. There's been a documented history of fishery declines in Lake Michigan for more than half a century and, over than span of time, we've always tried to adjust to those situations using the tools that are available to us, such as management and research and regulation. What we are doing with this session here is -- this probably was put together with the incentive or the interest of the decline of the yellow perch, mainly because of its impact that it makes on the community and commercial fishing and sport fishing and the perch just doesn't serve as another fish for a Friday night fish fry, either. It's more of an icon. So what we tried to do is use this word. In the title of all these presentations, the word "decline" shows up and, at the end of this 2½-hour session, you'll see how this weaves its way through.

We have four excellent speakers here. It's my pleasure to be here with them. I've known most of these people for a long time, practically my whole career. They will talk about the historical aspects of the fisheries in Lake Michigan, and you'll see how, again, this idea of declines weaves through all that, with all the different events or critical situations that have occurred over a long period of time.

Perhaps the most interesting or speculative kind of discussion we will have here with one of our presentations will be with regards to the exotics, and just how the exotics impact fishery declines. Then we have this perch thing we are going to focus on because, as I said, it's very important to us. Then we have the on-going salmonid situation in Lake Michigan where they were stocked back in the early '60s, primarily as a biological controller and, to this day, they're still being done for that, but it's really evolved into this multi-million dollar sport fishing industry. But even within the salmonid thing, you can see there's a decline. It has to do with, perhaps, the forage base declining, then growth rates decline, then stocking rates decline. So, as I said, this word "decline" just weaves itself through all four of these presentations.

Without any further delay, I'm going to introduce our first speaker. It's Dr. David Jude from the University of Michigan. David has been at that place for at least two decades or more. He's done a lot of work on early life history of Great Lakes fishes but, perhaps, more recently, he's really got into this history of Lake Michigan and all the aspects of fisheries. He's going to start the morning off by talking about the historical aspects of Lake Michigan and fisheries declines.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

Historical Perspective on Lake Michigan Fisheries Trends and Declines

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Dr. David Jude, University of Michigan, Ann Arbor, Michigan

Thank you, Fred. What I'm going to try to do today is overwhelm you with all kinds of slides and talk about what I think is what Fred was kind of discussing, and that is, some of the themes that intertwine through the history of the Great Lakes. I will start with my usual slide.

I've got the talk broken down into four sections. In the first one, we're going to talk about the history of the Great Lakes, that's sort of the long-term history, what it was like in pristine times. Then I've got a second section where I call the apocalypse, where a lot of nasty things happened to the Great Lakes. Then I'll go into what I call the resurrection. Then, my last section is going to be impending doom, taking something away, I guess, from The Phantom Menace and the recent Star Wars things. That's sort of where I'm going, and I'll be discussing a lot of the different aspects of the fisheries declines, and other speakers will certainly get into details, so I'm going to go fairly rapidly through some of these things and hit on a lot of high points and low points, and try to give you a feel, a sense, of what the history of the Great Lakes were, what some of the patterns were, and some of the lessons I think that we can learn from looking at what has gone on in the past.

Of course, you all know that the Great Lakes are very important -- one of the largest fresh-water sources in the world. This is how they compare to some of the great lakes of the world. I need not discuss further how important they are to recreation, industrial use, domestic use and, of course, even aesthetics. They are very important in the Great Lakes.

As you know, fish populations are subject to a number of different factors. This is a slide that Phil Ryan used for Lake Erie. You've got top-down impacts where predators can affect it, and Brian is going to be talking about impacts of salmonids on the forage base. You've got environmental changes that can affect the lakes, and you've got bottom-up effects, that is, if we change nutrient input to the lake, there may be all other kinds of changes. Then we've got what he calls middle-out and, that is, you can have internal changes within the fish populations that can have very dramatic effects on fish populations.

I'd like to show you this slide that, a fish population, when faced with a catastrophic event, has sort of three choices. They can go extinct, they can compensate by increased growth or survival, or you can have sometimes competing species sort of take over some of the habitat and some of the food resources that that fish population normally would take. We'll be seeing a lot of examples of that today as to how this was manifested in the Great Lakes.

Ryder and Edwards back in, I think, the '70s put out a paper that the IJC sponsored where they talked about indicators of quality in the Great Lakes. This was one of the series of responses that they saw to stress, when a fish population was stressed. The mean size decreases. You've got life-span shortening. You've got pelagic organisms increase, benthic organisms decrease. You've got foragers increasing, top predators decreasing, euri-thermal or euri-bions, which are those with a wide tolerance, replace those with a narrow tolerance to water quality and other parameters in the lake. You've got food webs simplify, you've got food webs shorten, introgression occurs, reproduction declines, species rations change, number of species declines, mesotrophic forms up, and production declines. We'll see some examples of all of these things going on in the Great Lakes. I think we can keep this in mind when we think about what the current population levels are in the Great Lakes and what it all means.

I'd like to talk about what has gone on in the Great Lakes in terms of what I call the five horsemen of the apocalypse, that's overfishing, exotic species, eutrophication, habitat destruction, and toxic substances. These are the five factors that we continually hear about and will be intertwined in the talk when we discuss some of the changes that have occurred in the Great Lakes. Overfishing was probably one of the big ones that had big impacts on a lot of different fish populations, and they would have impacts near to port and, and as populations declined, they would go further out. We saw lots of impacts of overfishing, and it was one of the dominant things that changed fish populations. In some cases, it allowed the sea lamprey to take ahold, because some of the top predators were in decline. Some of the larger fish were depleted out of the population.

We've got exotic species and, of course, they have had some everlasting effects on the Great Lakes. We could do things about nutrients and toxic substances, but exotic species have had a tremendous impact on changing the populations in the Great Lakes.

We've had all kinds of habitat destruction, where we've gone in and modified the habitat, changed nursery areas, changed places where fish need to spawn in tributary areas, and fish populations responded to that. Dams put in on rivers that stopped salmon runs and other kinds of things.

We've also got eutrophication. I need not talk long about how Lake Erie was declared dead and all the sewage that was dumped in from the city of Detroit into Lake Erie. Scenes like this were common -- this is in Saginaw Bay where a lot of blue-green algae and other Cladophora washed up on the shores, dead fish, a very obnoxious situation developed.

Toxic substances. Toxic substances have also figured prominently in a number of fish population declines and also destroyed the ability of these fish populations to present a wholesome food supply to people of the Great Lakes.

Now I want to switch over to what I discussed earlier, pristine times. Of course, the Great Lakes are about 10,000 years old, and it was only the last 200 years that a lot of these changes have occurred. So what was the Great Lakes like in the early history before man got here? Well, in the primeval state, it was cold, well oxygenated lakes. There were numerous tributaries, and you can just imagine what some of these headwaters, where they flowed out in Lake Michigan, would look like, without any jetties, without any harbors, and all the different kinds of fish species that were there, a well forested basin, and year-round stream flows that were cold. The primeval fish -- two top predators, the lake trout and the burbot -- there were a number of chubs or whitefish species -- ciscos, they're called -- that inhabited the Great Lakes. The key thing about that is, these species inhabited the vertical and horizontal ranges of all the Great Lakes. They were very efficient, because they evolved in the Great Lakes of utilizing the food supply. That was one of the points that Stan Smith always made, is that has changed tremendously, and we're not getting the efficient trophic transfer, because of some of the changes that we've seen.

We had blue pike, which was a specially adapted fish for Lake Erie and also Lake Ontario that occupied mesotrophic habitats. We had a lot of lake sturgeon and, of course, Atlantic salmon in Lake Ontario and, of course, the usual nearshore fish -- bass, drum, and walleyes. For those of you who don't know what a burbot look like, here's a burbot and, of course, these two, they and the lake trout were the top predators in the Great Lakes during these primeval times. This is a lake whitefish, again, one of the premium species that occupied the lake and, of course, our ancient fish, the lake sturgeon gets up to 200 - 300 pounds and, of course, they were probably one of the first ones to be impacted in Lake Michigan when they started tearing up commercial fishermen's gill nets. And then, here's a picture of, these are bloaters, coregonis hoyi, but they certainly would represent the different coregonines species that inhabited all these different niches in the Great Lakes.

This is sort of a documentary of what the trophic food web would look like in the pre-1940s -- burbot, lake trout at the top, eating deep-water sculpin and coregonines, the coregonines would feed upon zooplankton and mysis and diaporeia, which we will talk about later. And then, you've got the species near shore, lake herring -- which was sort of the nearshore version of the coregonines -- and then yellow perch.

Now I want to move on to what I call the apocalypse and, of course, that is closely related to populations of man, and that would cover the period 1800 to 1960s and, of course, this is a period of time that populations in the Great Lakes basin increased, man first came in, and you can see some of these population increases are logarithmic and, along with that, came a number of different changes in the Great Lakes. I like this slide that EPA has put out to show the population levels in the Great Lakes and, of course, we had a movement from the St. Lawrence seaway on in as these population centers developed and commerce developed, and these are the place where the most impact and the most people are in the Great Lakes.

So early settlement, the first European settlers were explorers and lumbermen, there was fur trading and, of course, very destructive lumbering activities that resulted in the loss of forest cover, change in stream flows, and water temperatures became elevated. Lots of log rafts in the rivers destroyed the tributaries and, of course, then there were major fires that resulted from that. You see pictures like this. You can imagine what kinds of impact that had on streams. Some of these logs are still found in some of the tributaries to the Great Lakes. It left the landscape looking like this, as trees were cut down. A lot of changes in the watershed occurred because of the early activities of man. I'm always astounded at the ability of the early lumberers to get every pine tree in Michigan, for example. There's only a couple places left where virgin pine trees exist in Michigan and probably throughout the Great Lakes region.

So, the early fisheries, of course, were the lake trout and lake whitefish and the lake herring, the coregonine I mentioned to you that inhabited the nearshore zone. Then there were other of these chubs or deep-water ciscos that were a focus of the fishery, and yellow perch and lake sturgeon were fished, sometimes commercially but sometimes as by-catch, and they were destroyed, burned on the beach by the commercial fishermen.

As has been our usual folly in the past, that we thought the Great Lakes were infinite and tonnes and tonnes of fish were removed without any concern for conservation, and lots of different problems resulted because of that. This is the lake trout again, and was one of the main targets of the early fisheries. As you can see by this graph, there was a decline in all five of the Great Lakes, brought on by overfishing and, then, exacerbated and probably their final demise by the sea lamprey when they entered each of the Great Lakes.

The same sorts of problems occurred with the lake whitefish. Their populations declined tremendously, fortunately, not to extinction. Populations went down in Lake Michigan, Huron, and Ontario and weren't as adversely affected in Lake Superior. Of course, as I indicated, lake sturgeon was probably one of the earliest ones that were impacted by commercial fishing. They would get in their gill nets, and commercial fishermen didn't like that. It tore up their nets. They killed as many of them as they could. Actually, there was some use of them for, I think, eisenglass and meat as well. So they went almost extinct as well in a lot of the Great Lakes, and they are an endangered species right now.

This is the lake herring and, again, this lake herring was sort of the nearshore equivalent that inhabited that area of the Great Lakes. Their populations declined and are probably commercially extinct in Lake Michigan, Lake Huron, and Bay of Quinte. In Lake Superior, populations declined to very low levels. We thought they were going to go the same way they did in the other Great Lakes, and there was a miraculous increase in their populations in Lake Superior. So, they actually came back.

Of course, we have exotic species. The sea lamprey had a very dramatic impact on the fish populations, and all of you have seen these ugly scars that have been put on lake trout. It's said that they kill about 40 pounds of fish per sea lamprey in the Great Lakes. You can see how a fish with a scar like this would probably die. So there's been a big impact on fish populations because of sea lamprey predation. They started into the Great Lakes sometime around the early '40s, and they moved through all the Great Lakes and made it up into Lake Superior before Vernon Applegate finally found a way to control the early life stages of the sea lamprey, and we are still having some problems with them.

On the heels of the sea lamprey, when there were no predators left in the Great Lakes or very few, and very few competitors, some of the coregonines, we had alewife move in. They are a dual-purpose fish. They act as prey for other fish, but they are also predators on larval fish. They had a tremendous impact on the Great Lakes as well. Just to show you some curves, they hit a peak in 1966 when -- some of you may have seen this on the beaches -- I was still too young then -- but there was some tremendous accumulation on the beaches in the Great Lakes, caused us aesthetic problems, and everybody declared the Great Lakes dead at that point. Again, to point out that these are what we call pelagic species -- they swim around in the upper water and, again, had some real dramatic impacts on the fish populations.

These are some of my data from Lake Michigan. The alewife population declined, and there was a tremendous response right away from the yellow perch population, which increased tremendously and, also, the bloater population or this coregonis hoyi population also responded. We think that was a response to the lack of alewife predation on the larvae. There were several other species that responded as a result of the alewife decline.

Here is a curve of the alewife-chub relationship. It was a very dramatic sort of thing. We hardly caught any in our nets, and then suddenly, around '76 - '77, when the alewife population declined, we had this tremendous increase in coregonines. So, there's big changes that have occurred in the alewife population. Part of this is the fact that alewife are marine exotics. You've got a lot of what we call depensatory predators out there. They eat a set amount of alewife, no matter what their population levels are, so they have a proportionally larger effect on alewife when the alewife populations are low. We've got yellow perch out there which eat their eggs, their juveniles, and their adults. I think that alewife do okay in the presence of no predators and no competitors but, now that we are getting some of our native species back, the alewife is going to have a lot rougher time making it in the Great Lakes.

Then, exotic species. This is Ed Mills' graph that discusses the sort of pattern of exotic species that have gotten into the Great Lakes -- the usual rogue's gallery of exotic species, including some that we don't think of as exotic -- the brown trout and rainbow trout, but some of the more nastier ones are white perch, ruffe, and zebra mussels that have gotten into the Great Lakes. The primary mechanism of them getting into the Great Lakes has been ship ballast water, as you can see from this particular graph. So, that certainly identifies another problem that we need to work on a lot more.

When we look at the lamprey and the alewife, you can see that they got into the Great Lakes starting in the '20s and the '30s, and the point I want to make is that it took them 25 years to get from Lake Erie to Lake Superior. Some of the exotic species we have now are doing that a lot faster, for example, the zebra mussel probably made it through the Great Lakes in 2 or 3 years. They were first found in June of 1988 and, of course, they are throughout the Great Lakes, and have moved out of the Great Lakes basin into a lot of other areas.

Then we discussed the eutrophication problem, and you all are aware of the declaration of Lake Erie as being dead and, at that time, was because of all the nutrients and toxic substances that were dumped into Lake Erie and Lake Erie, as a result, had a big shift in fish populations over to goldfish, common carp, and channel catfish. Again, the public's expectations were none. The Great Lakes are dead. We don't have to worry about them. We don't even go there any more. That sort of set up an opportunity for fish managers to, and also the people concerned with water quality, to really clean up the Great Lakes and get us on a better track.

Of course, all fishery collapses associated with these changes -- lake trout, lake whitefish, lake herring, and the chubs, and we've had some problems with the yellow perch and, of course, the lake sturgeon was probably one of the first ones that that occurred at.

So there's been great changes and, again, these are sort of those five horsemen of the apocalypse I was talking to you about -- extensive pollution, lumbering, sewage enrichment, habitat changes, removal of the forests, there was collapse of the major predator species, and invasion of the aliens, alewives, sea lamprey and rainbow smelt. So, things sunk probably to the lowest level that we have seen in this sort of time period. We saw a change from what we saw in the pre-1940s from top predators -- burbot, lake trout eating deep-water sculpin, coregonines, and the coregonines feeding on mysis and diaporea -- this simple food web has now changed to one that is dominated by the alewife, and the alewife has had impacts on yellow perch, bloaters, deep-water sculpin, and other zooplankton. Then we've got the salmon and the trout at the top acting as the current number of top predators and they're having an impact on the alewives.

So, there's been dramatic and substantial changes in how the trophic structure of the Great Lakes -- this, of course, is most, best represented by Lake Michigan, Huron, and Ontario and how these changes are manifested. Again, one of the properties that Ryder and Edwards mentioned is that, fish that are large and benthic get replaced by small, fecund species. You can see that pattern shown here with the commercial catch as species like lake whitefish and lake herring and chubs are replaced by rainbow smelt and alewife in Lake Michigan, and a similar sort of pattern in Lake Erie where we've got blue pike going extinct, walleye populations declining and them being replaced by rainbow smelt, yellow perch, carp, and some gizzard shad and some of the other smaller pelagic species in the Great Lakes. Of course, with those changes come a loss in premium species and, as managers, lots of different problems result.

To summarize, lots of things happened in that time period -- lots of extinctions, we lost the blue pike in Lake Ontario, the lake trout went extinct in all four of the Great Lakes, almost in Lake Superior, deep-water sculpin extinct in Lake Ontario, Atlantic salmon lost in Lake Ontario, and we lost five or six of these deep-water ciscos in Lake Michigan. There's been tremendous changes as a result of those extinctions. There's been a great lake herring decline in all four of the Great Lakes and in Lake Superior, we know about the sea lamprey and when they came in, the impact of the alewife. Severe pollution occurred. We had severe eutrophication in Lake Erie. We lost the blue pike in Lake Erie and, of course, there was severe declines in lake sturgeon, lake herring, and lake trout.

This is the section I call the resurrection. I'm not to be giving you always bad news, what's been some of the good news that has happened in the Great Lakes. We are making progress and, I think, around the late '80s and 1990s, we're seeing some big changes in the Great Lakes which certainly portend well for the future of the fisheries in the Great Lakes.

Here's the data from the USGS surveys on trawling in Lake Michigan. You can see a tremendous decline in the alewife that I mentioned -- that happened around 1976, 1977 -- and the fish populations responded. We've seen a big increase in bloater populations, the coregonis hoyi, the smallest of the coregonine species complex and, as a result, there's been some changes in the Great Lakes because of the alewife decline. These are the number of salmonids that were stocked, as managers tried to take advantage of this big forage base in Lake Michigan, and we saw all these different predators -- lake trout, brown trout, rainbow trout and chinook and coho salmon -- being placed in the Great Lakes. And they did their job. A lot of alewives went down their mouths and, because of some cold winters, we saw a big decline in the alewife populations.

These are some data from diets of salmon in the '70s and '80s, data that we collected. You can see that 60 to 80% of the diet of these large fish -- all five of the species are shown at the bottom -- is alewife, and that is continuing to present. There's been some shift to other species, but these predators are still eating a substantial amount of alewives out there. Some decisions are going to have to be made with regard to stocking these fish. This is the curve of the number of salmonids stocked and the decline in the alewife which, presumably, was one of the goals when salmonines were stocked in the Great Lakes but, of course, that conflicts with people who want a put-and-take salmonid fishery.

Then we discussed the big response of yellow perch and bloaters that occurred after the alewife decline. Both of those populations have increased because of the alewife decline. Right now, we've got a situation in 1993 where bloaters dominate the forage base in Lake Michigan. We're seeing a lot more of the native species dominate there, and alewives are now relegated to a lot lesser position in the Great Lakes. So, that's good news, I think, for Lake Michigan.

We've seen some cascading trophic effects of this. The salmon ate alewife. That released pressure on the larger daphnia in Lake Michigan. As a result, daphnia, which eat algae more efficiently, reduced the number of algae in the water, and water clarity increased as a result. We've also seen, because of the decline in alewife, that we've seen native species such as yellow perch increase.

One other species that increased was the deep-water sculpin, which was also preyed on by the alewife. And we've seen burbot increase in the Great Lakes, which has been a cause for concern for managers, because of competition for what they view as the more valuable salmonine species.

Here, the other basic, I think, change that has been made with regard to management in the Great Lakes is the shift from commercial fishing to sport fishing. We're all aware of the implications of that and why it was done, but it is a significant change in how the Great Lakes fisheries have been managed.

So, we've got new fisheries. We've got lake trout that have stocked, starting in the late '50s and 1960s, we've seen really a success only in Lake Superior where it's been declared only wild stocks there -- there's no stocking that goes on in Lake Superior -- but we're still struggling with that in the other four Great Lakes Coho salmon, chinook salmon -- we've seen spectacular examples of that in the Great Lakes. Walleyes -- we've seen two good examples of that and, of course, we've got control of the sea lamprey now. And, as I indicated, there's been some tremendous success with regard to stocking the salmonines, as people catch large numbers of those. The walleye fishery in Saginaw Bay and that in Lake Erie has been declared a world-class walleye fishery, and all kinds of good attention has been brought to that.

We've seen the lake whitefish recovery now in all five of the Great Lakes. It's been, once again, one of those spectacular things that have occurred. The reasons they advance for that is the sea lamprey decline, banning of gill nets, refuges for lake trout are also being used by lake whitefish and they're spawning there, restricted harvest, stocking salmon which reduced the number of alewife which then reduced the amount of predation on lake whitefish, and favorable climate. So, again, a lot of the things that are being done on the Great Lakes, though they may be done for one particular species or another, may have a real, widespread effect and cause all kinds of cascading effects throughout the populations. This is the silver chub, which is endangered in Lake Erie, and its populations have increased.

We've also seen hexagenia come back in Lake Erie, which is a tremendous accomplishment. For those of you who saw them back when they were present, and then they were gone for so many years, to have them come back and be part of the diet of fish and the implications it has. I think back, when I got called by a reporter from Monroe and said, how do I get rid of all these rotten mayflies that are all over the streets? I said, well, you can dump tonnes of sewage back into Lake Erie, or you can dump toxic substances in there, and that'll take care of them. I think people don't appreciate what a big thing the return of hexagenia in Lake Erie and the implications for improving water quality have been.

Toxic substances -- we've seen a big decline in the amount of PCBs in lake trout fillets and also in DDT, so I think we're doing real well with regard to toxic substances as well. We've seen water clarity increases in all the Great Lakes, and we've had, I think, favorable actions where the alewife, where we've introduced new predators. For overfishing, we got control of the fishery, set up quotas, and really tried to manage that fishery so we can have sport fishing as well as a managed commercial fishery in some of these lakes. Eutrophication -- we've reduced nutrient inputs by improving the sewage treatment plants across the Great Lakes, and we've had tremendous success, I think, in reducing that and, actually, it might be a problem in some places as defined by some people. And I think we've had success in reducing the amount of toxic substances put in the Great Lakes. Of course, sea lamprey -- I think we've got control of that using TFM. Still a lot work needs to be done, but it was enough of a control for us to start thinking about rehabilitating some of the lake trout in some of the Great Lakes and some of the larger fish, whereas that would not be possible if we did not control the sea lamprey.

So, there's been a lot of changes from the 1950s to the present -- reduced nutrient loading, we've seen some zooplankton species changes, we've seen the alewife decline, salmon success, and sea lamprey control. So, there has been, I think, a lot of things that we can be proud of and looking at. Again, here's a sort of a quick review. I think we can now say that Lake Erie is alive. We've got hexagenia back, we have resurgence of lake whitefish, lake sturgeon are back in small numbers in a number of the lakes, we've seen good walleye fishing, lake trout are better than they were, deep-water sculpin are present in the upper Great Lakes and are providing food for some of the species, we've seen a burbot increase and lake herring success in Lake Superior, and we've seen the small-mouth bass increase in Lake Erie as a result of some of the water quality changes we've seen. There's been progress in the Areas of Concern, decline in PCBs, water-clarity increases, a big improvement in the Bay of Quinte because of reduction of nutrient inputs there, and alewife declines.

So, when we look into the future, what sorts of things do we see coming at us? What is sitting out there in the mist and might be of concern for the future? I've put down a number of things for that and, of course, this is my impending doom section. Jack Christie once told me, he said, you can't be too enthusiastic about talking about some of the good changes that are going on in the Great Lakes, because we've got a lot of work left to do. We can't rest on our laurels. So, this is sort of the things, I think, that we're going to have to be worried about in the future. Zebra mussels, of course. There are all kinds of impacts of them. We've seen some ecological impacts. You're certainly aware of those impacts on industry. We've seen native species decline, the clams decline because of that, and I don't think we've seen all the ramifications of what zebra mussels mean in the Great Lakes.

Tom DeLepa at NOAA has been working on this diaporea decline in Lake Michigan, which we attribute to zebra mussels eating all the algae and filtering out all the algae. These are some of the data -- up to 10,000 diaporea per square meter off of St. Joe, Michigan. This in the '70s and '80s when I worked there and, now, we've got a situation, and Tom has these data published, where there are a lack of diaporea in a lot of the Great Lakes. Diaporea are a very important food for small fish and main food for yellow perch at some life stages. In Lake Ontario, we are seeing the same kinds of impacts going on. Some fish there eat almost exclusively diaporea, such as the slimy sculpin. There's going to be lots of manifestations of this particular problem directly related to the zebra mussel.

We've still got toxic substances running through our trophic pathways. There's all kinds of problems with regard to that. My son drew this sort of food chain thing for the round goby. We've got round gobies eating zebra mussels and small-mouth bass eating round gobies, and man eating small-mouth bass. We don't know what kind of an impact that's going to do. We're currently doing research to address that particular issue.

I mentioned Lake Ontario has a lack of any kind of species in the deep-water abyss, so there's no vertical transport of nutrients or productivity from there. So something has to be done about that. I think, in the future, either restocking deep-water sculpin or perhaps some of the coregonine complex, to try to restore vertical vectoring of energy out of Lake Ontario.

We've still got the Areas of Concern with us -- lots of problems in all of those particular areas. And, most recently, in some of the samples that we collected from eastern Lake Michigan, we found zooplankton with tumors on them. These tumors have been recorded in Europe, but never before in the Great Lakes. We've found them now in eastern Lake Michigan, in Green Bay, in northern Lake Huron, in the St. Clair River, and I just got reports from EPA last week that some were found in Lake Erie. This is one of those things that we don't know what caused it, possibly zebra mussels, possibly toxic substances, possibly viruses. We don't know, but it's something that certainly portends evil, I think, for the future. Will it result in more tumors for fish? We don't know but, certainly, it's one of the issues that we're concerned about.

So, the first part of this impending doom, we've got zebra mussels. We still don't have hexagenia in Saginaw Bay. Toxic substances recycling still continues. Lake Ontario -- loss of species. We've got the Areas of Concern, tumors in zooplankton, and the loss of diaporea. The other thing that's going on is what we call oligotrophication. This is the decline of phosphorus in the Great Lakes. That has also had implications for fish populations. We've got exotic species such as the round goby making its way through all five of the Great Lakes, spawning in beer cans and raising havoc with slimy sculpins especially, but other ramifications of their distribution and impact remain to be elaborated. They're recently been found in the Flint and the Shiawassee Rivers in Michigan. So, they are moving around and, as most exotic species, they seem to do things a little bit different than our native species, and sometimes better. They spawn more often, they grow to larger size, they feed at night, and they are very aggressive.

Then we have the ruffe. It's moving south. Found in Thunder Bay, probably soon to reach Saginaw Bay and then into Lake Erie. The ramifications of that, when it hits Saginaw Bay and Lake Erie still remain to be manifested. The sea lamprey is still a problem in the St. Marys River. People are wrestling with that problem. Lots of the fish in northern Lake Michigan and Lake Huron are still being severely impacted by the sea lamprey there. We have not got the sea lamprey under control, and that's another area they're working on in trying to get control of.

We've got biphotrephes cederstromii, an exotic zooplankter that's entered the Great Lakes in the mid-80s and then, more recently, this predatory zooplankton got one of its cousins in here, cercophagus pengoi. This is another large, predacious zooplankter that's coming into the Great Lakes. It's found in Lake Ontario and, last week, found it in Grand Traverse Bay, so it's also in Lake Michigan. Again, the implications for this, its entry into the Lake Michigan ecosystem are unknown.

We've had a big increase in double-crested cormorants in the Great Lakes. Of course, they are fish eaters, and there's been lots of concern by commercial fishermen and other fish managers about what their impact will be on fish. We've also got the spectre of global warming and what kinds of changes from perhaps cold-water species to warm-water species that might occur.

So, just to review all of these, we've got the oligotrophication problem, exotic species, sea lamprey, no hexagenia, global warming, and two other items -- bacterial kidney disease that have haunted stocking of salmon in the Great Lakes, and the early mortality syndrome. We're making progress on both of those, but they also loom as problems in the future if certain conditions develop.

Then, we've got problems with yellow perch recruitment, which will be elaborated on by my colleagues later on today and, as you probably heard, there has been a lack of reproduction in Lake Michigan by yellow perch since the late-1980s. One of the hypotheses that I've advocated is, perhaps zebra mussels have an impact on algae and therefore zooplankton. There are starvation aspects of that, and also alewife-yellow perch interactions, where the alewife either prey on the larvae or compete with the larvae for food.

We've got white perch showing up in Green Bay and implications for them, impacting the yellow perch fishery there. Brian Belanger and Fred Binkowski are working on that particular problem in trying to elaborate that. Salmon stocking has gotten a lot of concern. The numbers stocked have been reduced in both Lake Ontario and Lake Michigan because of the reduction in the alewife supply. Again, this is going to be a touchy problem. How many is enough? How are we going to manage the salmon population in view of the decline in the alewife?

Then we've got continued assault on our wetlands, where nice wetlands are changed by destruction on the shores. We have the recent example of the Humbug Marsh on the Detroit River that's being developed and, of course, the demand for more marinas, more development, more condominiums along the Great Lakes.

Then, of course, the alewife decline and what implications that may have, as I discussed, is going to be real important problem in the future.

Again, going over these potential areas, we've got energy transfer efficiency problems that we're going to have to consider because of some of these changes that have gone on. Yellow perch decline, white perch increasing in Green Bay, salmon stocking, wetland losses, and decline in the alewife.

What does it all mean? I guess, as we peer into the future and try to predict the sorts of changes that are going on, I hope that you've got some sense of the beauty of the Great Lakes, how important the fish populations are, how man has changed those fish populations, and what some of the vectors were with regard to how those changes were made, and how we can protect ourselves in the future and make the correct changes for the Lake Michigan and the Great Lakes ecosystem.

This is my summary slide that kind of tries to put everything into perspective with the Great Lakes, from Lake Ontario to Lake Superior down, shows the sea lamprey coming in, the alewife coming in, and it took them 25 years to get through all five of the Great Lakes. It shows the apocalypse area in the middle, where we lost lake trout, white perch and then, toward the end, we can see how zebra mussels have gone through all five of the Great Lakes in very short time periods. So have the gobies, and the ruffe are sort of on their way to doing that. So we've certainly seen a tumultuous summary, I guess, or changes in the fish populations in the Great Lakes. And that's all I have.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

************************************************************

Fred Binkowski

If there are any questions, we'll deal with that. What I'd like to do is pass the microphone to the individuals asking the questions.

Maxine Appleby

I live here in Milwaukee and I'm an avid sport fisher on Lake Michigan. I wonder if you could just comment, given the scenario, what happened this year that was so different in the salmon population. We're just about breaking records every day on all of the Great Lakes. The charter captains are so beat up, because they are not used to catching 25 - 30 fish at a time, and they're not accustomed to catching coho salmon that are averaging about, anywhere between 12 to 24 pounds. And the same goes not just for Lake Michigan, but Lake Huron has got a fantastic catch rate. Lake Ontario, recently on the Lake Ontario fall fishing derby, the smallest fish, the smallest chinook was about 43 pounds. That's a pretty good size.

David Jude

I'm going to let Brian answer that question, since that is his area, but I can throw you out what I think is possibly part of the problem, and that is, we had, I think, a decline in effort in the Great Lakes. So, my guess is that there's been a reduced harvest by sport fishermen, because of the big decline that went on. So, there may have been fish out there, or they may have gone out deeper in the water, so I think more of them survived.

The other thing that happened is, in Lake Michigan, we did not see very many alewives this year, at least the adults. But, last year, in 1998, because of the nice, warm year, the El Nino year, we had an amazing production of young-of-the-year alewife. Those fish were so abundant that they didn't go offshore. Normally they go offshore as yearlings and stay in what we call the middle part of the lake. They didn't do tat last year. A lot of them stayed in-shore. I think a lot of the food that these salmon are eating is probably these yearlings that were out there in just tremendous numbers. To get them in-shore is very unusual. We seldom see them. So, my guess is that a combination of a reduction in the harvest of these salmon, perhaps them being off-shore and out of the range of the fishermen, and a bountiful availability of small alewives has resulted in a tremendous growth of the salmon. Maybe Brian can give his opinion when he gets up here. Brad -- I'm sorry.

Fred Binkowski

Are there any other questions?

Unidentified Speaker

You had mentioned how the sea lamprey had been controlled, and you didn't really go into any specifics. I was just wondering exactly what substance was used and how it controlled the sea lamprey.

David Jude

Well, back when the sea lamprey first got into the Great Lakes, the then U.S. Fish and Wildlife Service mounted a tremendous effort, and Vernon Applegate in Ann Arbor was the biologist who worked on trying all different kinds of substances to see which one would control the larval stage of the sea lamprey, because that's the most vulnerable stage. They go into streams and spawn, and then, as larvae, sit in the substrate and filter. They are not predacious until they get big. They spend from 3 to 13 years sitting in mud, filtering mud. So, you can go into streams, put poison into the streams, and kill off all the larval amoceytes. This lasts from 3 to 13 years. You don't have to go in there again and hit them again, because the fish that spawn in there again will take three years before they turn into what they call transformers, and those are the ones that enter the Great Lakes and become predacious. He was able to identify what we call TFM, which is the acronym for trinitrodiphenylmethyl-whatever, which was the chemical that killed the amoceytes. That's been used in the Great Lakes, and I think it costs from like 2 to 3 million dollars a year. The Great Lakes Fishery Commission mounts that program, and they've had pretty good success.

One of the offshoots of improving water quality was that, a lot streams that formerly were too polluted to allow sea lamprey to successfully spawn, are now functioning as ... [tape change] ... the fish they would save are not worth as much as it would cost to treat the St. Marys River. So, they are focusing in on areas, being real specific about where they put the TFM, and they're trying to get control of sea lampreys in the St. Marys River, as well, but it's not the only effort that the Fishery Commission is taking on to try to keep ahead of this exotic species.

Unidentified Speaker

What sort of effect does that substance have on fish?

David Jude

It is, at the right concentrations, pretty specific to larval amocyetes, but there have been incidences where fish species like brown trout and sculpins have been killed, and sturgeon, I guess, are quite susceptible to TFM as well. And I think invertebrates are moderately susceptible. So, you may have heard of incidents where that has occurred, but that is just the price we have to pay in order to keep the sea lamprey under control.

Unidentified Speaker

You implicated zebra mussels in the decline of diporeia in Lake Michigan and Lake Ontario. What evidence do you have for making that inference, especially if you begin to look at zebra mussel populations beginning to level or decline in Lake Michigan, and it appears as though the diporeia decline is relatively recent. In other words, the area of diporeia depletion continues to expand at the same time that zebra mussels may be leveling off or going down.

David Jude

Well, I have not worked on them directly, but I read Tom DeLepa's paper and I've talked to him about it. If you read the paper, there's been some changes in the other benthic populations -- oligochaetes -- but he does not attribute that to zebra mussels. He thinks that might be related to decline in phosphorus in the Great Lakes. So, it's intertwined, as usual, with other effects, but the impact on diporeia was so much more dramatic. Diporeia feed on the diatom rain, and zebra mussels are taking that diatom rain out. So, Tom was pretty confident that it was a zebra mussel-induced effect.

I can tell you my own feeling when I first found a zebra mussel in Lake Michigan when I was doing some seining out there. I thought, well, they are not going to amount to any impact in Lake Michigan, because it is all sand out there. But, after doing some trawling out there, you trawl up 5 or 6 gallons out on the sandy areas, they're covered dune grass, fingernail clams were covered with zebra mussels. So, they are out there and they are having an impact. The water clarity increased, just like in Lake Erie. So, it's pretty dramatic when you're out there and you see the kinds of effects. So, I don't have any problem believing that zebra mussels are certainly one of the main driving factors at the decline in diporeia.

Unidentified Speaker

May I interject? I do an awful lot of diving off of Chicago which is a glacial moraine, rather rocky, and I don't see any indication in the decline in zebra mussels. The rocks are covered over with zebra mussels. But when you see the numbers, it is clear that ... zebra mussels ... the smaller ones are there. But in terms of overall biomass ... And that system ... diporeia ... just around ... [apologies -- the tape is faint]

David Jude

John makes a good point. Southern Lake Michigan is very rocky. There's a tremendous number of zebra mussels there, and then when the water mass comes around there, because that's the way the water circulation patterns go, the zebra mussels are taking out all the algae. Then that water mass comes around and then it gets deposited around Grand Haven, because that's a deposition zone, and then all the diporeia there in the southern part of the lake, and all the way up to, I think, Grand Haven now, are the ones that are being affected. So, it's pretty good evidence to suggest that the zebra mussels are certainly the driving factor.

Fred Binkowski

We'll take two more questions. One over here.

Unidentified Speaker

Some of the literature that I've looked over over the past few years suggests that, while we've cut the number of sea lamprey, we've actually selected for a more robust population. If I remember correctly, the ratio to females has increased, so we have more females. They are reproducing at a younger age, and other things that I don't remember. But I am curious as to what the thinking is currently. This is a few years ago that I looked this over.

David Jude

I talked with -- I can't remember his name right now -- who published a paper on exactly that and he maintained the same thing. Maybe that was the paper that you've read, that the sea lampreys are getting bigger and that they are definitely having more of an impact. So, just based on that, I agree that that is probably a factor, but I don't have any personal knowledge other than what I've read.

John Jackson

Have you seen any connection between the levels, the rises and falls of toxic substances in the lakes, for example, in Lake Ontario, and the well-being of the fish?

David Jude

That's always been a difficult question to answer. Whenever people ask me, what's the smoking gun with regard to the connection between toxic substances in fish and what impact they've had on fish and what impact that they've had on man. There's been all kinds of studies in laboratories where high levels have had, caused problems in rats, and you've certainly heard about certain PCBs that act as endocrine disruptors and estrogen mimickers in rats and can cause an effect. But, at least I am not aware of any study that relates the toxicity or the amount of toxic substances to what we find in fish.

John Jackson

A number of studies on Lake Ontario have made a very good connection between the rise and fall over the past several decades.

David Jude

There may very well be. I'm not aware of it.

Unidentified Speaker

It seems to me, in your account about the sea lamprey that, as our harbors become cleaner and we remove these contaminants, it going to make these sea lampreys who are nesting in this sediment, we are going to have fantastic hatcheries. I think that we are seeing that now, and we are also, we are seeing the same thing with the cormorant population. So those two, as we clean up, which we are supposed to be doing and as that is the end goal, we are going to see more of these problems persist, especially with the sea lamprey. So we are going to actually see more areas that are being treated and more robust lamprey populations.

David Jude

I agree whole-heartedly with you and, again, that's the response of a fish population to changing environmental conditions, and that's the sort of thing that we would predict and the sort of thing that the Great Lakes fishery is working on, and you are well aware of the cormorant problem. People are shooting them and poisoning their eggs and trying to control the populations. So, again, they are interacting with man, and when man's goals are implicated, they are going to have a response, so I'm not surprised.

Fred Binkowski

We need to move on, so we can finish on schedule. Our speakers will be around, so for those of you who have questions and didn't have them answered, take an opportunity to talk with the speakers afterwards. Thank you, Dave, for that very thorough overview.

We are going to now go from this broad-brush stroke overview to focus down on exotics and what kind of role they are playing in the Lake Michigan story. I can't think of a more appropriate person to tell this story than Dr. John Janssen from Loyola University in Chicago. John's been working with the exotics, and he understands them probably best, because I think he can communicate with them effectively. John will attack this issue with regards to exotics. I'm not exactly sure which ones he's going to talk about. So are just going to put him up there and let him do his thing.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

Effects of Exotic Species Introductions on Fish / Perch Populations

************************************************************

Dr. John Janssen, Loyola University, Chicago, Illinois

I'm going to set up a video.

I'm going to start off with a slide of some people that I'm absolutely afraid of running into every time we launch the boat, because what's going to happen is that they are going to ask me a whole bunch of questions about how are the perch doing this year, why are they so scared, why are the salmon growing so big this year, why were they growing so poorly before. All these questions, so I kind of like to wear a disguise, try to skulk around, but they always find me and hit me with these questions. It's a little fearsome just to launch a boat with these guys harassing me all the time.

Looking at the flip side of that, there are some people that I actually love to see -- there they are! -- because these guys are actually out on the water constantly. They must be absolutely rich to spend all that time fishing, and they are always telling me things that are really, really important, like, we think we are seeing some round gobies over here, you want to go check it out. It looks like maybe there are some juvenile yellow perch over here, you want to go check that out. Maybe they are sending me on wild goose chases, but they actually give me a fair amount of useful information.

My sort of point for that is that, even that we've got people like the four speakers today and other people who are employed to go out and research Lake Michigan, in some sort of sense, we are all researchers on Lake Michigan, at least particularly the anglers, because you are going out and seeing things, and there are many more eyes out there than just the science community. It's everybody that might see something interesting. As evidence for that, generally the instances of exotic species showing up, particularly fishes, come from the anglers, not so much from the scientists. So, at any rate, we are working together on this whole thing.

Now, I'm going to start off with a slightly different frame of reference. I want to talk about exotic species and ecosystems in general before talking about Lake Michigan, so I could think of no better place to start than in my own back yard. So, here is my beat-up back yard. This is a disturbed ecosystem. This beast back here, whenever we come home, starts running in big circles and she digs up divots of grass and stuff. She occasionally fertilizes different areas of the back yard. My wife and I dig this little path here to the garage and stuff. The vegetation back there is alien species. They are not native plants to Illinois. There are some dandelions, the white clover from here is in Europe, all the grass species -- there are about 4 or 5 grass species in there now, they are all European grasses, where lawns originated -- etc. Now, when we moved into the place, we sort of made a compromise. We figured, well, we wanted some kind of lawn back there, but you don't want a high-maintenance lawn. Right? Because if you have a high-maintenance lawn, it cuts down on the amount of time you can spend with the dog playing, or out fishing, or something like that. So, the woman that lived here before had the absolute industry-standard blue grass monoculture lawn. I looked at that and said, wow, is that high maintenance. She has to fertilize it. She has to put herbicides on it. There were no earthworms, which meant that she was pulling off the lawn clippings and probably using pesticides on there, and I didn't want my dog running around in the pesticides. So, what we did was we cut down the watering that first summer. At night, I'd sneak off to the various parks where the grass was still green and full of weeds and, wherever she'd kick up some divots, I'd put little plugs of stuff from the parks in there. Now, despite a relatively dry summer -- we've watered the grass three times during the summer -- well, it's not industry standard, but it's tolerable.

Our neighbors, on the other hand, have the industry-standard blue-grass lawn here. It's very entertaining to watch them watering it constantly. It just got re-sodded, which they do every couple of years, because they're doing all the things that the plants don't want, like pulling off the lawn clippings and stuff like that. That's very expensive.

So, our lawn is some kind of compromise between this very-expensive-to-maintain lawn and -- what I'd probably really like to do, except my wife won't let me -- is turn the lawn into a prairie. We have a 5-foot by 5-foot prairie back there. This used to be all ragweed in this little corner right here, but what we did instead was we went to local plant dealers, got prairie plants and, within a year, we have a system that, from May until October, has something in flower, so at least there's some color in there. It's zero maintenance. We don't have to weed it at all. We don't get ragweed in there like it used to be in there. Right now, there's butterfly weed, there's some bachelor button in flower here. This is it, about a week ago, coming into its fall glory, with the white aster and, right now, this purple aster is pretty much filling up this bit here. So, that's very nice sort of low maintenance.

So, a natural ecosystem without very much tampering is very, very low maintenance. If you want an ecosystem that's going to perform certain things for you, like provides lots of one or two fish species, or four or five fish species, then it's going to be high maintenance, particularly if you have other kinds of disturbances.

So, this is actually almost a synopsis of one of Dave's last slides showing impacts. And this is focusing on aquatic organisms that have been introduced to the Great Lakes. Not all of them but ones that are certainly noticeable. So, a bit over a hundred years ago, carp introduced, apparently as a political project, not as a project initiated by anglers. Rainbow trout and brown trout. Rainbow smelt introduced to a lake in Michigan that was connected to Lake Michigan and got to Lake Michigan. Here's our first big whopping invasion of sea lamprey, and I'm not going to say that these are definitely the costs, but they are numbers I managed to find in terms of maintaining this ecosystem -- what are the costs of maintaining the ecosystem after you get this kind of invasion. Alewife coming in in the latter part of the 1940s as indicated by Fred initially. The salmon initially put in as a pest control on the alewife, and that's sort of an approximate estimate, thanks to Dave Clapp there, I hope, of how much it costs to maintain that predator control. The nice thing about this is that there is a monetary feedback because people are out there fishing for them. Somewhere I found this number as the cost of zebra mussels, which is probably mostly for industry having to clean them out of pipes, etc. But this is sort of a brief synopsis of some major invaders, including one that we think is probably going to be a major invader, but probably not the impact of zebra mussels.

Let's look at them. This is actually not a sea lamprey. I wish we could get lampreys that were sucking down on carp. That would solve a lot problems. This is one of the native lampreys, but there's a lamprey. This is an old photograph from around the Shedd Aquarium in Chicago during the 1967 die-off of alewife, and you can imagine, this was a huge cost to try to clean that up, so that people would actually go to downtown Chicago and other cities. That's the predator control. Here are these guys back to haunt me, and then zebra mussels, and the last little exotic -- this is from the first goby fishing competition down at Calumet Harbor in 1974, and I think that was the largest one caught. They are about this big now down there. One of the fishes that the goby is displacing down there is this -- it's a mottled sculpin. In our part of Lake Michigan, that's an important forage for the perch, and they're pretty well being knocked out by the round gobies. Whether this will replace them as a prey item is something we don't know, or how effective they will be to replace them.

Now, actually the Great Lakes have a long history of disturbance, though not necessarily man-made, and that affects what's happening with exotics now. As Dave indicated before, the glaciers left here about 10,000 years ago -- that's not so long ago -- so this is a drawing from a book of glaciers scouring out Lake Michigan, and the fishes that are native to Lake Michigan and the Great Lakes are not things that are particularly well adapted for the Great Lakes. I wanted to use these distribution maps as evidence of that. Yellow perch is found all over the northern part of North America. Spottail shiners -- one of the commoner minnows you would see around shore -- is also found in a much broader area than just the Great Lakes. Emerald shiners. Even the lake trout isn't so much a lake trout as a big river trout, particularly when you look at the distribution up here. Lake whitefish isn't so much a lake white fish as a large river whitefish, where it's found up in here. And the ciscos aren't so much lake organisms as large river organisms. These all turn out to be organisms that happened to have some characteristics that allow them to live in a large lake.

So this is descriptions from "A Field Guide to Freshwater Fishes." Yellow perch -- lakes, ponds, pools, creeks, and small-to-large rivers. In ponds and lakes, they tend to over-reproduce and become stunted because there's too many of them. So, they reproduce very well in such situations.

Spottail shiners -- sandy, rocky pools and runs. I don't see Lake Michigan on there at all, but it's certainly abundant there. Emerald shiner -- the same kind of thing. Lake trout, you may be surprised -- restricted to relatively deep lakes in the southern part of its range, our part of the range, in shallow and deep waters of northern lakes and streams. Lake whitefish -- lakes and large rivers. Cisco and lake herring -- open waters of lakes and large rivers. So these fishes have characteristics that allow them to prosper, if there is not a whole lot else in something the size of Lake Michigan, but they are not particularly adapted to something like Lake Michigan, which leaves the lakes invasable to things that might be better adapted to large bodies of water.

I'm going to get to some consequences of that. I'm going to bounce over to perch for a while, and then we're going to come back to exotics. The description of what happens to perch during the first month, month and a half of their life, is pretty much based on a paper that came out in the mid-80s, based on a lake in Minnesota called Lake Icasca, which is a small lake. Now, one of the things that we've discovered in working on yellow perch in Lake Michigan is that, whatever determines the year-class strength, that is, how good reproduction is for a year, is probably determined in the first month to month and a half of the fish's life. So this is really, really important. So, the fish spawn sometime in the spring, they do what's called a pelagic migration, that means they tend to go offshore, they're not close to shore and, after about 40 days, maybe a little bit younger, they'll come near shore and feed on things that are associated with the bottom. While they're out here, they're feeding on small little animals, little zooplankton-type things.

What I wanted to do was to run some video at this point, to give you, maybe, a better idea of what it might be like to be a baby yellow perch. This is a perch egg mass from Lake Michigan we got during a dive. It's a big gelatinous mass maybe about that long, and there'll be thousands and thousands of eggs in there, and you can probably see them as individual dots.

Unidentified Speaker

Is that from more than one fish?

John Janssen

No, that's one fish, one female. This is some daphnia swimming around in a tank but, here and there, you'll see some baby perch just a couple days old. If you're lucky, you'll see one actually feed on something. It will form a little S-loop with its body and leap at something. Now, the stuff that they're feeding on is much smaller than the fish. It's too small to actually show up on the camera. This actually looks a little bleached out with the projector. The larger dark things in here are all daphnia, a large species of daphnia, which is a common zooplankter and even that's too large for these little fishes to feed on at this stage in their life.

Here's the larger daphnia in here, but the stuff that's important for these small perch to feed in are these smaller things swimming around here. Here's a close-up on this. This is the very earliest stage of something called a copepod, called anopeleus. That's a juvenile copepod. Here's another little anopeleus that darted off there. Another type of copepod here. Well, some other things in there. But that's what the baby perch have to find to feed on very early in this life. This is a relative of biphotrephes, the spiny water flea, a little bit bigger but something that a perch would feed on later during this pelagic phase of its feeding. This one's given the name polyphemus. That's something that perch would feed on -- it's called a bosmina -- while they're still quite small, something around 10 mm.

And, to finish it off, we have a nice spiny water flea biphotrephes coming into view, as soon as we've got it there. Big, ugly monster, and actually the perch, as they're about the size that they'd be coming ashore, seem to be feeding on a fair number of these. Is that right, Dave?

David Jude

Yeah. They'd be about 100 mm.

John Janssen

Let's shut the video off and go back to slides. I hope that gives you a better idea of what's like to be a tiny little perch in a very big lake.

The data that we have from Lake Michigan, this is what I've sort of gathered from a group that we call the yellow perch task group, which is a bunch of researchers all around Lake Michigan, including Wisconsin, Michigan, Illinois, and Indiana. This is data from 1998. What I've indicated on here is a larval peak, when they were reporting the most number of larval perch, and when they started first seeing juveniles coming ashore. What you get here is a gap of about a month to 40 days in which the perch are basically offshore and, in terms of our present sampling technology, we haven't been able to catch them yet, probably because they are too dilute, or at least that's my thought on it. So this is consistent on what happens in the small lake, Lake Itasca, in terms of timing between when the larvae hatch and when the juveniles start coming ashore at about that size, about 4 inches or so, 3 to 4 inches.

The other thing that's interesting, and it's not explicit on this, is that the abundance of the larvae and the juveniles -- I don't have numbers on juveniles here -- varies considerably around the lake. Last year, the highest abundance of larvae occurred up in northern Michigan here. The highest number of juveniles occurred in Indiana, with some lesser numbers further south in Michigan, but almost no juveniles in northern Michigan. This year, from the data that I'm seeing on the e-mails, the highest abundance of larvae came out of Chicago. We had a whopping load of larvae. I haven't seen a juvenile perch in Illinois. There's been a few at the Illinois-Wisconsin border, and Wisconsin has gotten a few, and there's sparse, but better, numbers in Michigan, but still extremely sparse. So there seems to be some kind of disconnect. Where you have an abundance of larvae doesn't mean that's where you're going to get an abundance of juveniles. And, that's probably a matter that we're dealing with a very, very large lake that has large currents.

Now we go to the third part of the media. Actually, let's do the slide.

Lake Michigan gets large water currents because it's so big and the wind can have such a big effect of it. This is something called an upwelling, which the anglers will be familiar with, where you have cold water near shore, generally a wind going like that -- let me get the pointer again. These are temperature lines. That line indicates a constant temperature, and over here at Muskegon, there's a shore temperature of 7^o centigrade, which translates to the middle degrees Fahrenheit. Over here, in Chicago, the temperatures are in the mid-70s, and the warm water has been pushed from east to west because of the wind conditions in this, a very old diagram of this. So, the warm water essentially gets blown off shore.

Let's go to the overhead. With what we call an upwelling, what might happen to a bunch of baby perch is, assume that we had a bunch of larval perch hatching here, along the Michigan side, with the warm water, where they're hatching, moving offshore. What's going to happen to those baby perch is they're going to get pushed off somewhere like that, so they're offshore, that on top of their tendency to move offshore. What happens to them after that can get very complicated and in ways that we don't totally understand.

Because the currents get more complicated than that, I really love this diagram for complication, when the wind shifts, particularly if it comes out of the north, you can get eddies of currents, moving water around like this, you get patches of cool and warm water. We saw some of that this summer. You look at the temperature readings off of your own recording instruments, and you sometimes run into cool patches and you're, like, where did that come from? Well, it's because of the strange currents. You can get jets of water that, if you imagine some baby perch here, that gets swept offshore to somewhere off here. So, for that reason, it's going to be probably very unpredictable where the juvenile yellow perch -- if they survive, which is a big question -- are actually going to come ashore.

I pulled out some -- this is from the late '70s -- this is drifting buoys being monitored by a satellite over a two-month period, but most of what happens, happens in a month. What these people did was, they deployed one, two, three, four buoys off Muskegon at various distances and the satellite tracked where they were. So this is a recording of where the satellites drifted. If you look at this, you can see basically that it's very unpredictable where a particular buoy would go. Here's several that, well, one that beached down in southern Michigan, and then here's this one that beached way up here north of Frankfort.

If you imagine a patch of larval perch that have been swept out to the middle of Lake Michigan, where they're feeding on zooplankton -- there's pretty good zooplankton abundance out there -- but if you imagine that, instead of a buoy here, you have a patch of larval perch, it's going to be very hard to predict where a bunch of perch that were spawned here are going to end up, or where a bunch of perch that were spawned off of Chicago or Milwaukee are going to end up in that 40-day period. They could end up just about anywhere, which is probably the reason why, where we get the largest number of larvae -- one year here, the second year here -- does not predict where we are going to get the largest number of juveniles. So, figuring out what's happening to these perch during this critical month is going to be a very, very difficult sort of problem.

But there are fishes that are better adapted to that kind of situation, and those are marine fishes, particularly fishes that spawn offshore. Now, alewife is a marine fish, but it is a little different because it spawns in fresh water ponds, which are fairly predictable types of habitats in terms of water currents. There's not a lot of water currents and stuff. Rainbow smelt also run up small streams, so they're not putting their babies into currents, and this is the only native fish on this whole diagram.

What I've done is pair these fish that you're familiar with, with some strictly marine fish that spawn in a marine environment, and this is how they deal with an unpredictable large environment where wind creates lots of water motions. If you don't believe that, look at some of the North Carolina hurricane stuff. The alewife spawns for one or two months, in any particular area, just a couple of weeks. The Atlantic herring spawn from April to November, an extended spawning period. The rainbow smelt spawns for a month in Lake Michigan, a couple of weeks in any particular area. Its nearest marine relative, the capelin, a huge commercial fish off Newfoundland, spawns from June to August, several months. The yellow perch -- two weeks. The bluefish, that's about the closest thing I could find marine, spawns from June to August, very extended spawning periods. It's a way of dealing with a very unpredictable sort of environment.

So I made this cartoon to try to put this in some kind of perspective. Here we have a perch at the gambling casino and, to get a good year class, it's got to have enough food for its babies, it's got to avoid being eaten, it has to avoid not being blown off to what I've just called Oz, some place where the larvae aren't going to live, and it says, I gamble once a year, and every few years I win, which is sort of the pattern we see. Every few years, if the perch are lucky, they get a good year class. It's just been a long time since we've had a good year class.

Here's a marine fish. It says, I gamble early and often -- which is pretty much how people vote in Chicago, early and often -- and most of those particular gambles will fail but, because the fish is gambling so often, each year it usually wins, that is, it gets some good spawns in that year. This is, we would argue, a matter that this is a fish not adapted to strong currents in big bodies of water. This is how you adapt to those and, in 10,000 years since the glaciers left, there hasn't been enough time for that kind of adaptation to occur.

Now I actually want to divert a little bit and blunt something I hear a lot from anglers which is, well, if the perch year classes are so variable, it's hard to get much spawning success, why don't we stock perch? For that, I want to actually defer to another authority -- a book here, and he's not here to answer questions -- but this is what the enlightened fish managers think about stocking these days. So I'll read this for those of you who can't read it, because you're further back. It says, Supplemental stocking is an intuitively appealing approach to addressing issues of stock deplacement. If it wasn't intuitively appealing, we wouldn't have so much stocking going on in the first place, and a long history of it. However, such efforts have proven to be more destructive than helpful to many wild fish stocks. As an example, nearly a century of stocking fall-run chinook salmon into the Little White Salmon River contributed to the extinction of the native stock because of the introduction of new genetic strains. Then it goes on for pages with other catastrophes, based on trying to augment populations by stocking.

Now, actually, a place that hasn't had much stocking yet sort of provides a good illustration of this enlightened approach to fisheries management. My wife and I were up in Alaska about a month ago -- this is a bunch of coho, she caught them all, I can't catch them -- they look small next to the Michigan ones now, right -- they guides that we talked to pretty much claimed that they could pretty much recognize what run of coho they were getting, that is, what stream they would spawn in. They would just say, well, that's from such-and-such a river, that's from such-and-such a river. I won't vouch that they're that accurate, but I actually believe it. The fact that these things home to particular streams and, therefore, have their own genetic races, affects the management of the system.

I don't expect you to read all this, but this is the regulations for fishing for trout and salmon around Juneau, Alaska. So there are all these streams going in here, and every bloody little stream has its own little regulation, and that's all designed to try to maintain the genetic stock for that particular stream. Now, a lot of these streams get fish stocked into them, but they catch fish that are native to that stream. They raise those fish in that stream, and then they release them in the stream. They clip them as they're released, and they'll let you catch lots of fin-clipped fish, but they'll allow you to harvest almost no fish that are wild fish and that. So they're trying not to destroy the genetics of the system. They've learned the mistake that we've made down in the lower 48 states about stocking.

Fishery managers are very concerned about stocking things, augmenting the perch population by stocking, for fear that we might ruin something that's special about the Great Lakes perch, something that's evolved in the last 10,000 years.

Let's get back on target here. We're in the situation where we'd like to enhance the perch population or at least predict what's going to happen to them, if and when we are going to have good year class strengths. So, let's go back to this diagram showing the early life history of a yellow perch, and I want to ask sort of a question, these are sort of rhetorical questions, and the first one goes something like this -- you have three researchers here, the authors, who took two years to work this out on Lake Itasca. Let me pull that up once more -- if it takes three researchers two years and a lot of previous background to figure out what goes on to figure out what goes on in something like Lake Itasca, which is -- that's about the size of Lake Itasca, I couldn't get a good drawing of its size on there -- you know, that's a trivial lake. What is this, with Minnesota is the land of lakes? The land of trivial little lakes. Okay? Now you compare that to Lake Michigan, that's small, small lake -- that's trivial next to Winnebago, and Winnebago is trivial next to Lake Michigan.

Actually, maybe the one lake in which we have the best sort of model of what controls perch populations comes from a lake in England. This is a European perch. It's a little bit different than ours. You'd probably mistake it for our perch, but these things get to 8 pounds. I've seen 4-pounders in Europe, and I can see somebody wants to stock those, right? Don't do it! At any rate, in Lake Windermere, which is -- that's about the size of Lake Windermere, it's about 15 miles long, it's skinny -- we have sort of the best model of what happens to a perch population, what controls its year-class strength.

So, this is actually an old paper, but I like the graph better than the more recent stuff. This is sort of a map of Lake Windermere here. It says 10 km, so that's about 6 miles there, and Windermere has several basins, so it's not one distinct lake, and you see that there's some correlation -- oh, and we have a time range from the '40s and this is to the early '60s, and this actually extends in some other graphs to the '70s, but they're kind of not as interesting -- so you see that, you know, in some part of the lake, you get a good year class here in 1955, here's another one in '55, but some other basin doesn't get such a good year class. So, even with a lake that size, you get this disconnect between different parts of the lake, variation in year-class strength of the European perch.

So, we shouldn't be surprised that we get a disconnect in Lake Michigan, between where we get lots of larvae and lots of juveniles. They came up with a model that you won't be able to read from there, but let me go through it of factors -- actually, it's a contingency diagram -- of factors that affect perch reproduction. This was put out actually about 20 years ago. So this actually sort of an axis here with, towards the bottom here, you have reproductive failure -- not many juveniles that year -- and at the top here, we have success. Now, that's not drawn as a graph line, but think of success as being something up high here and failure as something down low here.

Over here, we have basically questions, and the first question that you ask, if you are going to predict Windermere perch recruitment is temperature. If it's relatively warm, you're more likely to get a good year class. If it's relatively cool, a poor year class. I think that's probably happening in Lake Michigan.

Second question is, you ask about how much food there is for the larvae -- those little tiny things that were swimming around in the vide -- and that can be low, or intermediate, or high. Actually, that's right here. Then you ask about predation. The predator in this case is a predator on the juveniles, not on the larvae. It turns out to be the pike, which is not very abundant at all in Lake Michigan, so it's certainly not a factor there. Then there's questions about ice cover. Well, we don't get serious ice cover on Lake Michigan.

But this is the kind of diagram that we'd like to generate and attempt to get at it is, I think, what Dave Clapp is going to talk about. This is what we'd like to have for Lake Michigan, but we have this problem in terms of actually generating it, and this is going to get back to exotics.

So, here's a comparison. Here's the diagram that we had for Windermere for 20 years, with the populations going up and down in the different basins, and there's also records of the pike population and the food population, the temperature, and stuff like that. Here's the diagram I had earlier -- it's titled on its side -- showing invasions. If you take a 20-year period -- let's take a 40-year period -- from alewives first showing up in Lake Michigan -- the sea lamprey's already been there -- you have all these changes in the lake in that time, plus some other ones.

Windermere has the luxury that they've got the same biota that they started with over that 40-year period. We have the problem -- the difficulty -- that our biota keeps changing over those years. One of the big problems, we think, is probably this guy, the alewife, that may be the last thing that a baby perch sees is the gill-rakers inside an alewife mouth. Dave will probably talk more about that, right Dave? Good.

But as researchers and the people that are managers, this is sort of the problem that we've got, which I've stolen from ...

[At this point there is a 30-minute recording gap]

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

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David Clapp, Michigan Department of Natural Resources, Charlevoix, Michigan

Accompanying Visuals(Large PowerPoint Presentation - Slow downloading)

Questions and Discussion

Abstract

Catch of adult yellow perch in Lake Michigan declined dramatically between 1988 and 1998, and the population age structure shifted toward older fish due to an almost complete lack of recruitment. Steps taken to address this decline included coordinated regulation of commercial and recreational yellow perch harvest, and formation of a multi-agency Yellow Perch Task Group to expand research aimed at identifying likely causes for the lack of perch recruitment.

Three hypotheses currently being addressed by activities of the Yellow Perch Task Group are:

• Mortality at the egg stage influences yellow perch recruitment;

• Inappropriate diet limits survival; and

• Alewife predation limits recruitment.

There appears to be little evidence to support the idea that factors at the egg stage directly influence perch recruitment, but experiments have shown a relationship between adult female yellow perch size and GSI and larval perch length and yolk volume. This relationship suggests that building spawning stock diversity will produce offspring with enhanced probability of successful recruitment in a variable environment.

Lake Michigan zooplankton populations have changed considerably between the 1980s and 1990s, and evidence collected to date shows a significant positive relationship between zooplankton density and yellow perch survival. Additionally, long-term data collections in southern Lake Michigan continue to show a negative relationship between alewife abundance and yellow perch recruitment. Maternal factors, diet, and predation probably act in concert, along with harvest and "natural" density-dependent functions, to regulate yellow perch abundance. Successful management of perch populations will require knowledge of the interrelationships among all of these factors.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

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Brad Eggold, Wisconsin Department of Natural Resources, Plymouth, Wisconsin

... of those early days. Here's a graph of harvested lake trout in Lake Michigan from 1920 to 1965, and you can see, back in the '20s and '30s, we were harvesting about 2 to 3 million kilograms of lake trout, essentially going down to zero in the early 1950s. So they did have a profound effect on the lake trout populations, obviously.

At that the same time, alewives came into the St. Lawrence Seaway through the same way the lamprey came in and did, again, have a dramatic impact on the prey biomass at the time. As Dave mentioned -- I guess he was too small to remember this, but, luckily, I wasn't born at this time but, so, similar -- in the 1950s, '60s, and '70s a common occurrence of dead alewives showing up on the beaches, many times many feet thick. The ancillary effects of these coming into the lake and washing up on the shores is that people didn't want to go down to the lakefront any more. Many of the towns that had been set up through commercial fishing of lake trout and lake sturgeon, in the early days of some of these small towns, like Cheboygan and Port Washington in Wisconsin, people didn't want to go down there any more because they had this scenario going on. So, it was a big problem at that time.

Well, in the mid-1960s, Dr. Tanner created some of these slides that are steps toward a Great Lakes sport fishery and, right now, as we saw the situation in the early '60s, alewives were dominant and there was a need really to reduce their abundance. Sea lamprey had been brought under somewhat control in 1960, and we started stocking lake trout in those years, and there was a deep-water predator, the lake trout, but there was still a need to get at some of these alewives that were in the upper water column.

The fact that we had lake trout, we still needed some more predators. So Dr. Tanner advocated that we needed to stock salmon and trout. And it was an opportunity not only to reduce the alewife population but, hopefully, produce a sport fishery. In addition, he thought that, by stocking salmon and trout, we'd control the alewives, we'd have a sport fishery on salmon and trout, but an extra dividend might be valuable in-shore species would be coming back. And, in fact, we saw this in the '80s and '90s that today, much of his vision in 1967 has come true. We've seen a reduction in the alewives through predation of salmon and trout, we've seen other in-shore valuable species like yellow perch, small-mouth bass, and others are once again abundant to some degree. So, it has actually provided an excellent fishery.

When we think about it, when we stock salmon and trout, is the salmon and trout fishery and it actually has been a world-class fishery. We've got anglers from all over the United States as well as the world come to catch huge trout and salmon, and we have people come in from Alaska, the west coast, and marvel at the size and number of fish that we can produce in Lake Michigan. So, it really was a huge success.

A typical catch on a boat fishery might be lake trout, chinook, and really is a mixed bag of all species -- chinook, coho salmon, brown trout, and rainbow trout.

In addition to the boat fishery, we also have a tremendous fishery in our streams that feed into Lake Michigan. We stock these streams with the salmon and trout and, in the fall and the spring, anglers go back into these stream to catch it. Catch-release has become quite popular in recent years, as people go into these streams with fly-fishing equipment and catch some of these huge chinook salmon and rainbow trout that come back into these streams.

Once we had salmon and trout stocked in Lake Michigan, we wanted to find out what's going on with them, how do we know how many are harvested, what are some of the conditions -- growth, size -- so many of the state agencies created creel surveys along Lake Michigan and, through the use of creel surveys, we were able to get the number of species harvested -- the numbers, weights, growth rates, and diet compositions of the catch in Lake Michigan.

In addition to the creel survey, because we needed to catch returning salmon and trout to capture the gametes, many weirs were set up on streams flowing into Lake Michigan. We were able to get return rates, growth rates, as well as some health factors of fish returning to these weirs.

If you take a look at the harvest of salmonids in Lake Michigan from 1920 to 1997, we can see this kind of picture. Where we had lake trout in the early days at between 2 and 3 million kilograms, essentially going down to zero in the 1950s, now we're seeing a harvest of about a million kilograms per year. In addition to lake trout harvest again, we are also seeing a harvest on brown trout, rainbow trout, coho salmon and, to a dominant degree, chinook salmon. You can see where, back in the early days of the fishery, we were harvesting under 3 million kilograms, we are now probably harvesting at least that much in the lake trout combined with the other salmon and trout.

What the salmon and trout fishery has done is really revitalize many of the towns and lake shores along Lake Michigan. Where had people not wanting to come down to the lake front in the '50s and '60s and '70s, now people were coming back down there. They were coming down to fish for salmon and trout. Improvements in access to marinas prevailed. We saw a lot of development -- I guess for good or bad -- down at the lake front, which really brought a lot of people in down to those areas.

Nearshore species such as the yellow perch, small-mouth bass were again present in the fishery. Many of the harbors and nearshore areas of the lake were once again teeming with these nearshore species. It really provided a huge economic benefit for not only these small towns and cities but also the entire region to have people come here and fish for these salmon and trout. Contests like the Cheboygan coho derby again cropped up all over Lake Michigan, bringing people back down to the lake front and enjoying the catching of salmon and trout. Where we might have seen nobody on the piers in the '50s and '60s, we now saw large amounts of people down there. What really brought about these changes, if you look at the Lake Michigan fish community, pre-1900 the major predators were lake trout and burbot. In post-1970, we looked at lake trout stocked as well as burbot and the other salmon and trout species.

The planktivores went from seven species of cisco, two species of whitefish -- lake herring and emerald shiner -- really to one species of cisco -- the bloater chub -- two species of whitefish and, of course, the two exotics, smelt and alewife.

The benthivore fish community -- lake sturgeon, four species of sculpin and suckers pre-1900 switching to suckers, the two species of sculpin, and carp.

Once these planktivores came in and the two exotics -- smelt and alewife -- really are the major components of the prey fish biomass in Lake Michigan, if you take a look at the graph, and we've seen this several times today, the biomass in tonnes of the different prey fish, you can see that, prior to 1983, the alewife really dominated the prey fish biomass. Since 1983, chubs have really come on and now constitute a large percentage of the prey biomass in Lake Michigan.

Well, once we started to have the alewife under somewhat control, we became kind of concerned that, maybe, those levels were getting too low and we might have some problems on the horizon and, in fact, that's what happened. If you look at sport fishing effort from Wisconsin and Michigan anglers -- Wisconsin has a continuous creel survey since like 1969 -- we saw our fishing effort start to decline through the late 1980s. As well as Michigan who started its creel program and saw a sharp decline in sport fishing effort in the late 1980s.

More troubling than the sport fishing effort is probably the chinook salmon catch rates. Here we see catch rates from Wisconsin and Michigan anglers and you can see, in the late 1980s, we were up at around 0.18 fish per hour, dropping drastically in the mid- to late-1980s. So, combined with the catch rate, we knew that something was going on and, in fact, we started seeing dead any dying chinook showing up on our beaches in the late 1980s. Bacterial kidney disease was the likely culprit. It's a stress-mediated disease brought on by starvation and poor nutritional diet. We saw a lot of our chinook salmon at that time succumbing to this disease and washing up dead and dying on the beaches.

Now, BKD had been around in Lake Michigan for some time, but it had never really manifested itself in the dramatic fashion that we saw in the late 1980s and, indeed, from like 1987 through 1990, there was a lot of mortality on primarily chinook salmon but other salmon and trout as well.

When we took a look at all those factors involved -- we looked at the prey fish biomass, we looked at what was going on with chinook salmon catch rates, we then looked at annual stocking of salmon and trout in Lake Michigan and what we saw was that, at the mid-1980s, we were stocking a lot of salmon and trout, and the feeling is that there was not enough biomass out there for them to eat. So, in 1991 Wisconsin, Illinois, and Indiana reduced stocking of chinook salmon by 25% to reduce the forage pressure on alewives and to reduce the potential for starvation and the onset of bacterial kidney disease. We instituted that in 1997 and I think it had some effect. We were able still to maintain a pretty good fishery through the 1990s. We saw Lake Michigan was still capable of producing large fish through the 1990s.

Really, fishing since 1994 really has been tremendous for salmon and trout. In Wisconsin alone, since 1995, we've broken our record fish once for chinook salmon, twice for steelhead, twice for brown trout, and once each for coho salmon and brook trout. We've seen a kind of an oscillating. We've had a tremendous fishery through the mid-1980s. We did see some decline in the late 1980s and early 1990s.

More recently the salmon and trout population seems to be in much better shape. Well, fisheries management was still a little concerned, and we took a look again at the prey fish biomass in Lake Michigan. Again, if you look at the current status that we have now -- chubs making up 70 to 80% of the prey fish biomass, and then alewife and smelt. Well, even though it seems to be a fairly large biomass, somewhat diverse, what is actually available to salmon and trout? We looked at the estimated prey fish biomass that was really available to trout and salmon in those years, and you can see a much different story, primarily alewife available, some smelt and some juvenile bloaters. So, really, the number of prey fish that we had out there available isn't that big when you look at what really is available to most of the salmon and trout.

We kind of verified this with some diet studies that were done by Rob Elliott over in Michigan. He looked at age-3 chinook salmon diet in 1994. Here we have different areas of the lake. We also have each bar represents a different season, and you can see that age-3 chinook salmon dominated by alewife. Even though we 70 - 80% bloater biomass out there, the chinook salmon prefers preying on alewife. There are some bloaters in different areas of the lake, but a very small amount.

In addition to age-3 chinook salmon preying heavily on alewife, we also have adult coho salmon preying on alewife as well. Again, in most parts of the lake, at most seasons of the year, they rely heavily on alewife for their main forage consumption. There is some insects in the south as well as some smelt in different areas but, again, the majority of coho are seeking out and finding alewife.

When we look back at the standing stock of chinook salmon in Lake Michigan, we can see -- and we modelled this after what we saw -- there was an increasing standing stock of chinook salmon through the middle of the 1980s. Then, through probably overstocking, too many predators in the lake, not enough alewives, we did see the chinook salmon population plummet in the late 1980s and, more recently, we've seen that standing stock of chinook salmon go up. Just like for the yellow perch, where we convened a conference in 1994, in 1998 we convened a lakewide stocking conference. We wanted to find out from fishermen around the lake what they wanted to see. Do we continue stocking chinook salmon and have levels approach this red line [on a visual aid] which might again get us back to the situation we had in the mid-1980s. We might see another population crash of the chinook salmon.

Or, we could go another route. We could not stock any fish and rely on natural reproduction, primarily in Michigan streams to provide the fishery. Well, in fact, what we decided to do was to try and hit this target level -- 90% of the consumption that was present in the mid-1980s. We were going to try and hit this range in terms of standing stock for chinook salmon. What we decided to do was, once again, reduce chinook salmon stocking by 25%, hopefully so that sufficient forage exists for not only chinook salmon in the lake but other salmon and trout, and that the population drop that we saw in the late-1980s would not occur again.

In trying to convince the sport-fishing public -- it was tough back in 1991, when we said, well, we're going to reduce stocking by 25%. Then we said, well, in 1999, we're going to reduce it again by 25%. When we looked at the chinook salmon harvest versus stocking, we saw that, through most of the years of stocking, as we stocked more we got a higher harvest. Well, in more recent years, primarily since 1990, it seems like the more fish we stocked, or if we levelled off at that amount, we don't see a continued rise in the harvest rate. So we feel very comfortable with that. By reducing stocking by 25%, it will allow for a healthier and larger chinook and also a healthier and larger salmon and trout population.

Where have we come from and where will we go? You can see that exotics like alewife and sea lamprey had a dramatic effect on the Lake Michigan ecosystem when they first were introduced, as well as continuing today. Stocking of salmon and trout helped control the abundant alewives and really produced a world-class fishery. I really can't emphasize that enough. We've had people come from all over the United States as well as other countries and really marvel at the kind and size and type of fish and the mixture of fish that they can catch in Lake Michigan.

Really, the heyday of the salmon fishery occurred from its inception in the mid- to late-1960s through the middle of 1980, and that kind of stopped when dead and dying chinook started showing up on the beaches. The fisheries managers of the time decided to reduce stocking by 25% in 1991, to address this lower forage biomass that we saw primarily in alewives and, again, even though recent harvest and catch rates for chinook salmon are relatively good, in 1999 we again reduced chinook salmon by 25% lakewide to ensure long-range stability in the Lake Michigan ecosystem.

Some other presenters have touched on some other Lake Michigan fisheries populations, like whitefish and burbot seem to be expanding. We see good, healthy populations of lake whitefish, primarily in the upper part of Lake Michigan, the Green Bay area, as well as burbot are expanding. Nearshore populations like small-mouth bass, walleye, and northern pike are growing and, as we see more non-point and point source pollution controls, we're seeing harbor areas produce excellent small-mouth bass, walleye, and northern pike populations.

Really, I think, in general, the Lake Michigan salmon and trout populations seem to be relatively stable at this time. We're still enjoying good catches and large sizes of salmon and trout. Because they are able to control the alewife, I think they are also allowing other populations like small-mouth bass, walleye, and northern pike to become established in some of our nearshore areas, as well as have an effect on other Lake Michigan fisheries, like lake whitefish and burbot.

There are still some work to be done, obviously, primarily with yellow perch recruitment but, I think, overall, in general, Lake Michigan fishing for salmon and trout as well as other species is definitely bright. Thanks.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance

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Fred Binkowski

I guess we'll take some questions.

Unidentified Speaker

Back in the late-80s, when the alewife started their quick decline, and I know a lot of fish biologists were predicting -- I don't think any of them will admit it now -- a shift heavily over to coregonids and, obviously, that hasn't happened. Is there any research thinking about why that is? Is it strictly a recruitment (?) effort? For one thing, they just don't share the same part of the lake the same time of the year, ... or are they doing most of their eating of bloaters and chubs offshore, ... or that they're just harder to catch? What's the current thought about why they haven't taken more ... of this?

John Janssen

I think to answer your first question, when we first looked at bacterial kidney disease in the late '80s and early '90s, there was some thought that we could have some switching over to bloater chubs, and there was some in the upper part of Michigan where they might consume 30 - 40% bloaters, but everywhere else it seemed primarily on alewives. I don't think they like to eat them, and I think the spatial concern about, they don't occupy the same water column at the same time, they're more of a deep-water species, does not have them come in contact with chinook salmon and the other species as much as you might think. If you looked at that biomass, the tremendous amount of chubs we have, and yet they still aren't eating them. I wish they would. It would probably help us out quite a bit.

Unidentified Speaker

My question is more general. When you considered the different stocking options for 1999, and you considered no stocking, I think, you know, that conversation, what did you consider? When you considered no stocking, we you looking at just no salmon, or no stocking at all? For how long? What were your predictions of what the effects would be?

Brad Eggold

I think because we tried to focus on chinook salmon, primarily because of their huge impact on the alewife population. If you look at the consumption rates of chinook salmon compared to the other ones, they'd probably eat three or four times as many alewives as any other stocked salmon or trout. And when we looked at reduction of the chinook salmon stocking as zero, essentially the only chinook salmon then in the lake would be from some natural reproduction in Michigan. I think the thought at that time that it would be too low a level to control the alewife population and we might see the alewife rebound to such a degree that we would have problems with other nearshore species, like yellow perch, and have them, as Dave mentioned, as a delicate balance between how many alewives do you have out there, how many fish do you stock, compared to making sure you have a healthy population of salmon and trout, and also try and have a nearshore fishery. You have to remember, we had most of these sport-fishing public at that meeting, so I don't think that the no-stocking option was really debated all that heavily.

Unidentified Speaker

What are the estimates of natural reproduction in Michigan waters of chinook salmon? How does that factor into the whole stocking decision?

Brad Eggold

What we did, when we took a look at how many fish we were stocking, we tried to augment that number with how many we thought were coming out of Michigan, and I think the prevailing ideas about possibly 2 million smolts a year. Now, obviously, with wild production, that probably oscillates between 2 million to zero on an annual basis, but we tried to factor that into our decision to reduce the stocking, knowing that we were getting some natural reproduction, and maybe the reason why we saw the problems we started to see was maybe that more natural reproduction was contributing to the chinook salmon recruitment and, therefore, we had more predators than we really thought in the lake, really driving down the alewife biomass, so we took that into consideration when they modelled this, and that's why they went for a fairly drastic cut of 25%.

Fred Binkowski

Any other questions? With that, I'd like to say thank you for coming, and I'd like to give a special thanks to our four speakers. As I said, it was my pleasure to be here with these four people, because I have worked with most of them, and I have known a couple of them for my entire professional career. So again, thank you for coming. I hope that we've provided some valuable information, and we'll keep you posted and updated on how we're doing in our efforts to try to solve the perch problem and any other important species decline on the Great Lakes and Lake Michigan. Thanks again.

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INDEX

Historical Perspective on Lake Michigan Fisheries Trends and Declines

Effects of Exotic Species Introductions on Fish / Perch Populations

A Multi-Agency Effort to Address Declines in Lake Michigan Yellow Perch Abundance