These developments include:
Tillitt and coworkers conducted preliminary evaluations of
visual/motor function of viable swim-up lake trout develop-
1.
the demonstration that early mortality syndrome-like
ing from eggs with very low thiamine concentrations (<1
symptoms can be induced in the laboratory by a
nmol/g) and “normal” thiamine (> 10 nmol/g).  Preliminary
thiamine deficiency or by the application of thiamine
results indicate statistically significant deficits in the low
antagonists;
thiamine group compared to the “normal” group in terms
2.
the implication that inadequate egg thiamine may be
of detail discrimination (visual acuity) and motion detec-
associated with reduced fry recruitment even if the fish
tion (flicker fusion thresholds) evaluated both in photopic
7.3
survived overt mortality;
(day vision) and scotopic (night vision) conditions.  This is
3.
the confirmation that the amount of thiamine degrad-
consistent with other recent studies investigating predator
ing activity in the two exotic forage fish species
avoidance or prey capture (Fitzsimons et al. 2002).
(alewife and smelt) was up to one hundred times the
Investigations on the effects of predator avoidance and
activity observed in the native bloater species;
zooplankton foraging showed significant but variable
4.
thiamine concentrations in forage fish is adequate to
relationships, depending on egg source, between thiamine
meet nutritional requirements but that thiamine
concentration and predator avoidance by fry.  These studies
degrading activity (thiaminase) can be highly variable
set a tentative egg thiamine threshold of effect at 3 nmol/g.
within a species (temporal and geographic variability)
Together, these findings indicate that a majority of the lake
as well as differing among the prey species that
trout and salmon populations are vulnerable to low
elaborate the enzyme; and
thiamine and this may represent a major component in
5.
the isolation of  two microbial strains of thiaminase
understanding the present day lack of recruitment of lake
positive bacteria from alewife viscera suggesting this as
trout in the Great Lakes.
one possible source of thiaminase in these prey
species.
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