Addressing Concerns for Water Quality Impacts
from Large-Scale Great Lakes Aquaculture

Based on a Roundtable
Co-hosted by the Habitat Advisory Board of the Great Lakes Fishery Commission
the Great Lakes Water Quality Board of the International Joint Commission

August, 1999


The Food and Agriculture Organization of the United Nations defines aquaculture as the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. Aquaculture began in the Great Lakes in the late 1800s, but experienced an increase in the number of operations in the 1980s. Currently, there are more than 1,000 Great Lakes aquaculturists.

There are several different types of aquaculture operations. The majority of Great Lakes operations are located on land. Land-based operations grow fish or other freshwater food products in ponds, tanks, or containers filled with water. Water quality impacts and permitting of land-based operations are generally more easily managed than in-water operations because the water from these operations is released at one point or pipe.

In-water operations consist primarily of net pens or cages. These nets are fashioned in the form of a large, floating bag which contains the fish, but allow water and waste to flow freely in and out. Currently, there are fewer than 15 caged aquaculture operations in the Great Lakes basin and numbers vary annually. All of these operations primarily raise rainbow trout for human consumption. Net pens or cages vary in size and production, but can have surface areas as large as 370 m2 and can hold 100,000 fingerlings or 30,000 larger fish per cage. As well, many operations have several cages operating at any one time.

Aquaculture is openly promoted by several organizations and government agencies. Indeed, aquaculture provides a much needed alternative to depleting wild stocks of fish and other products. The industry also provides employment and spin-off economic benefits. However, aquaculture can become an issue when an operation has a negative impact on a public trust resource, the water body where it is located. Environmental problems have led to moratoria on the expansion of sites for salmon caged aquaculture operations in three of the world's largest producers of farmed salmon - Norway, Ireland, and Chile (Goldburg and Triplett 1997), and for a time in British Columbia, Canada. Some Great Lakes aquaculture operations, as seen in the case studies provided in this report, have impacted the resource as food waste and fish waste increased loadings of phosphorus and nitrogen leading to reduced water clarity and algal blooms. Fortunately, the majority of aquaculture operations have been properly sited and well managed to ensure a minimal water quality impact.

The future of aquaculture in the Great Lakes is difficult to project. Although the per capita consumption of seafood in the United States is not expected to increase, the demand for seafood is expected to increase in line with the increase in population. Site selection for aquaculture is limited by current available technology, as well as physicochemical suitability. U.S. and Canadian markets are sensitive to world markets affecting price and this, combined with the everyday difficulties associated with other forms of intensive agriculture such as disease, feed costs, weather, etc., will impact the economic viability of aquaculture.

The roundtable was held to encourage discussion of Great Lakes aquaculture, to provide a forum for objective and scientific evaluation of water quality impacts associated with fish and fish feed wastes and to encourage further investigations. However, this report only addresses water quality impacts of large-scale Great Lakes aquaculture. Other issues such as exotic species, disease transfer, use of therapeutics, etc. may be important and must be addressed in the future by management when considering growth and expansion of the industry. It appears the best documentation of water quality impacts comes from large-scale aquaculture operations; this report did not address issues and management concerns which may be unique to small fish farms operating within the Great Lakes watershed.