Increasing Thiamine Concentrations in Lake Trout Eggs from Lakes Huron and Michigan Coincide with Low Alewife Abundance

Abstract

Lake trout Salvelinus namaycush in the Laurentian Great Lakes suffer from thiamine deficiency as a result of adult lake trout consuming prey containing thiaminase, a thiamine-degrading enzyme. Sufficiently low egg thiamine concentrations result in direct mortality of or sublethal effects on newly hatched lake trout fry. To determine the prevalence and severity of low thiamine in lake trout eggs, we monitored thiamine concentrations in lake trout eggs from 15 sites in Lakes Huron and Michigan from 2001 to 2009. Lake trout egg thiamine concentrations at most sites in both lakes were initially low and increased over time at 11 of 15 sites, and the proportion of females with egg thiamine concentrations lower than the recommended management objective of 4 nmol/g decreased over time at eight sites. Egg thiamine concentrations at five of six sites in Lakes Huron and Michigan were significantly inversely related to site-specific estimates of mean abundance of alewives Alosa pseudoharengus, and successful natural reproduction of lake trout has been observed in Lake Huron since the alewife population crashed. These results support the hypothesis that low egg thiamine in Great Lakes lake trout is associated with increased alewife abundance and that low alewife abundance may currently be a prerequisite for successful reproduction by lake trout in the Great Lakes.

Received January 4, 2011; accepted July 20, 2011

ACKNOWLEDGMENTS

We thank the many individuals that collected eggs for thiamine monitoring, including Steve Robillard and Dan Makauskas (Illinois DNR); Brian Breidert and Randy Brindza (Indiana DNR); Tom Burzynski and Bradley Eggold (Wisconsin DNR); Steve Lenart (Little Traverse Bay Band of Ottawa Indians); Erik Olsen (Grand Traverse Bay Band of Ottawa and Chippewa Indians); Archie Martell (Little River Band of Ottawa Indians); Sergiusz Czesny (Illinois Natural History Survey); Dale Hanson, Mark Holey, Scott Koproski, Adam Kowalski, and Aaron Woldt (U.S. Fish and Wildlife Service); Ji He and James Johnson (Michigan DNR); Mark Ebener, Amanda Handziak, and Greg Wright (Chippewa Ottawa Resource Authority); and Adam Cottrill, David Reid, and Jeff Speers (Ontario Ministry of Natural Resources). Courtenay Vining, Michael Gabor, Kimberly Smith, Christina Accardi, Blake Snyder, and Robert Gerroux provided technical assistance during sample analysis. Clifford Kraft, Don Tillitt, David Warner, and two anonymous reviewers provided comments that improved the manuscript. John Van Sickle (U.S. Environmental Protection Agency, Corvallis, Oregon) provided helpful statistical advice. D. Bunnell provided alewife abundance data for Lake Michigan. This work was funded by the USGS–GLSC, the USGS Leetown Science Center, the Great Lakes Fishery Commission's Fishery Research Program, and the Great Lakes Fishery Trust. This is Contribution 1638 of the USGS–GLSC. Reference to trade names does not imply endorsement by the U.S. Government.