by
Department of Fisheries and Wildlife
University of Minnesota
St. Paul, MN
Lake trout were sampled from Lakes Michigan and Superior to determine their thiamine nutritional status. Trout from Lake Michigan consistently had lower levels of thiamine in their blood and eggs than did trout from Lake Superior. A thiamine destroying enzyme, thiaminase, contained in the predominant forage items of trout from both lakes, smelt or alewives, may decrease levels of thiamine in blood and eggs. Lack of successful natural reproduction by Lake Michigan lake trout may be related to their reduced thiamine nutritional status.
At present, about 40 years after the demise of native lake trout (Salvelinus namaycush) in the upper Great Lakes and the initiation of a massive program of lamprey (Petromyzon marinus) control, the goal of re-establishment of self-sustaining lake trout in Lake Michigan has not been achieved (Holey et al. 1995). This is in spite of the fact that tremendous numbers of lake trout have been stocked for over 30 years and that lamprey populations are a fraction of peak abundance. In contrast, naturally reproducing lake trout populations have been reestablished in most of Lake Superior (Hansen et al. 1995). Among the many possibilities for why self-sustaining lake trout populations have not been reestablished in Lake Michigan is a nutritional problem related to the forage base currently available to lake trout. The current study was based on the hypothesis that the diet of lake trout in the Great Lakes contains thiaminase which causes a thiamine deficiency which in turn impairs reproductive success.
Alewives (Alosa pseudoharengus) and smelt (Osmerus mordax), which are major components of lake trout diets in Lakes Michigan and Superior, respectively, contain a thiamine destroying enzyme, thiaminase (Gnaedinger 1964) which may lead to a thiamine deficiency in fish that consume a high proportion of those forage species. Such a nutritional deficiency may result in sub-normal reproductive success because thiamine is an essential vitamin for fish (Halver 1972). Recent studies have implicated thiamine deficiency as the cause of early mortality syndrome (EMS) of Lake Erie and Ontario lake trout larvae (Fitzsimons 1995, and Fisher et al. 1996). EMS symptoms are maternally transmitted and include loss of equilibrium and death at the time of yolk sac absorption. If this syndrome is widespread, it may contribute to the poor reproductive success of Lake Michigan lake trout.
The objective of this study was to determine differences in the thiamine nutritional status between adult female lake trout in Lake Superior and Lake Michigan. A reduced thiamine nutritional status in Lake Michigan lake trout may help explain why re-establishment of naturally reproducing lake trout has been more successful in Lake Superior than in Lake Michigan.
Field Collections
Sampling sites for adult lake trout were in the vicinity of Saugatuck,
MI for Lake Michigan and Bayfield (Apostle Islands), WI for Lake Superior
(Fig. 1). Successful reproduction of lake trout in the Saugatuck area of
Lake Michigan was non-existent whereas naturally reproduced lake trout were
common in the Bayfield area of Lake Superior (Hansen et al. 1995, Holey
et al. 1995).
Lake trout blood was sampled several times in each lake during 1987 and 1988. For purposes of comparison, these sampling times were designated as pre-spawning, spawning, and spring seasons. Fish were captured in gill nets from the Saugatuck area by the U. S. Fish and Wildlife Service except for the spring sampling in 1988 when fish were captured by angling from a charter boat. Samples obtained from the Bayfield area were gill-netted by the Red Cliff Chippewa Band, the U. S. Fish and Wildlife Service, or the Wisconsin Department of Natural Resources.
Egg samples were taken during the fall spawning season whenever possible. Eggs were stored on dry ice during transport and at -20° C in the laboratory before analysis.
Blood Sampling and Analysis
Blood and egg thiamine pyrophosphate (TPP) levels were used as an indicator of lake trout thiamine nutritional status (Masumoto et al. 1987). Five to 10 ml of blood were drawn from the caudal artery of female fish that were still alive when the gill net was pulled. The blood samples were placed on dry ice during transport and were stored at -20° C until the analysis.
TPP levels in blood and eggs were determined by high pressure liquid
chromatography (HPLC). The procedures of Baines (1985) were followed with
minor modifications. 
This work is the result of research sponsored by the Minnesota Sea Grant
Program supported by the NOAA Office of Sea Grant, United States Department
of Commerce, under grant No. R/F-23. We are indebted to personnel from the
Red Cliff Band of the Chippewa, the U.S. Fish and Wildlife Service, and
the Wisconsin Department of Natural Resources for assistance in collecting
fish and to George R. Spangler for providing the intellectual impetus to
conduct this research.
Baines, M. 1985. Improved high performance liquid chromatographic determination of thiamin diphosphate in erythrocytes. Clinica Chimica Acta 153: 43-48.
Conner, D. J., C. R. Bronte, J. H. Selgeby, and H. L. Collins. 1993. Food of salmonine predators in Lake Superior, 1981-87. Great Lakes Fishery Commission, Technical Report 59, Ann Arbor, MI.
Fisher, J. P., J. D. Fitzsimons, G. F. Combs, Jr., and J. M. Spitsbergen. 1996. Naturally occurring thiamine deficiency causing reproductive failure in Finger Lakes Atlantic salmon and Great Lakes lake trout. Transactions of the American Fisheries Society 125: 167-178.
Fitzsimons, J. D. 1995. The effect of B-vitamins on a swim-up syndrome in Lake Ontario lake trout. Journal of Great Lakes Research 21 (Supplement 1): 286-289.
Gnaedinger, R. H. 1964. Thiaminase activity in fish: an improved assay method. Fishery Industrial Research 2: 55-59.
Halver, J. E. 1972. The vitamins. Pages 29-101 in J. E. Halver, editor. Fish Nutrition. Academic Press. New York, N.Y.
Hansen, M. J., J. W. Peck, R. G. Schorfhaar, J. H. Selgeby, D. R. Schreiner, S. T. Schram, B. L. Swanson, W. R. McCallum, M. K. Burnham-Curtis, G. L. Curtis, J. W. Heinrich, and R. J. Young. 1995. Lake trout (Salvelinus namaycush) populations in Lake Superior and their restoration in 1959-1983. Journal of Great Lakes Research 21 (Supplement 1): 152-175.
Holey, M. E., R. W. Rybicki, G. W. Eck, E. H. Brown Jr., J. E. Marsden, D. S. Lavis, M. L. Toneys, T. N. Trudeau, and R. M. Horrall. 1995. Progress toward lake trout restoration in Lake Michigan. Journal of Great Lakes Research 21 (Supplement 1): 128-151.
Masumoto, T., R. W. Hardy, and E. Casillas. 1987. Comparison of transketolase activity and thiamin pyrophosphate levels in erythrocytes and liver of rainbow trout (Salmo gairdneri) as indicators of thiamin status. Journal of Nutrition 117: 1422-1426.
For more information contact:
Ira R. Adelman, Ph.D. Professor Department of Fisheries, Wildlife, and Conservation Biology University of Minnesota 1980 Folwell Avenue St. Paul, MN 55108-6124 U. S. A. Phone: 612-624-4228 Fax: 612-625-5299 e-mail:ira@umn.edu
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Wildlife, and Conservation Biology Date created: Sept. 5, 1996 Last modified: June 16, 2005 Copyright © 1996, Ira AdelmanIRA@umn.edu