Egg Thiamine Status of Lake Ontario Salmonines 1995–2004 with Emphasis on Lake Trout |
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Authors: | John D Fitzsimons Bill Williston Georgina Williston Lisa Brown Abdel El-Shaarawi Lenore Vandenbyllaardt Dale Honeyfeld Don Tillitt Martha Wolgamood Scott B Brown |
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Affiliation: | 1 Fisheries and Oceans Canada, Bayfield Institute, Burlington, Ontario L7R 4A6;2 Fisheries and Oceans Canada, Prescott, Ontario K0E 1T0;3 Environment Canada, National Water Research Institute, Burlington, Ontario L7R 4 A6;4 Fisheries and Oceans Canada, Winnipeg, Manitoba R3T 2N6;5 Northern Appalachian Research Laboratory, USGS, Wellsboro, Pennsylvania 16901;6 Columbia Environmental Research Center, USGS, Columbia, Missouri 65201;7 Michigan Department of Natural Resources, Wolf Lake Fish Hatchery, Mattawan, Michigan 49071;8 Deceased |
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Abstract: | Alewives (Alosa pseudoharengus), the major prey fish for Lake Ontario, contain thiaminase. They are associated with development of a thiamine deficiency in salmonines which greatly increases the potential for developing an early mortality syndrome (EMS). To assess the possible effects of thiamine deficiency on salmonine reproduction we measured egg thiamine concentrations for five species of Lake Ontario salmonines. From this we estimated the proportion of families susceptible to EMS based on whether they were below the ED20, the egg thiamine concentration associated with 20% mortality due to EMS. The ED20s were 1.52, 2.63, and 2.99 nmol/g egg for Chinook salmon (Oncorhynchus tshawytscha), lake trout (Salvelinus namaycush), and coho salmon (Oncorhynchus kisutch), respectively. Based on the proportion of fish having egg thiamine concentrations falling below the ED20, the risk of developing EMS in Lake Ontario was highest for lake trout, followed by coho (O. kisutch), and Chinook salmon, with the least risk for rainbow trout (O. mykiss). For lake trout from western Lake Ontario, mean egg thiamine concentration showed significant annual variability during 1994 to 2003, when the proportion of lake trout at risk of developing EMS based on ED20 ranged between 77 and 100%. Variation in the annual mean egg thiamine concentration for western Lake Ontario lake trout was positively related (p < 0.001, r2 = 0.94) with indices of annual adult alewife biomass. While suggesting the possible involvement of density-dependent changes in alewives, the changes are small relative to egg thiamine concentrations when alewife are not part of the diet and are of insufficient magnitude to allow for natural reproduction by lake trout. |
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Keywords: | Thiamine EMS alewives lake trout Lake Ontario |
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