The Green Bay National Fisheries and Wildlife Conservation Office (NWFCO) surveyed spawning lake trout on Clay Banks Reef in western Lake Michigan.  The annual surveys were completed between October 14^th and November 8^th with a primary objective of collecting lake trout eggs. 

Eggs were collected from live fish that were captured during over-night gill-net sets.  Eggs obtained from Clay Banks, along with eggs collected by other agencies at various locations throughout Lakes Michigan and Huron, are being analyzed at the USGS Great Lakes Science Center for thiamin concentrations. 

Lake-wide egg thiamin levels are of interest because in some areas eggs are deficient in thiamine and this may lead to high egg mortality.  Thiamin deficiencies have been linked to fish diet and therefore continued monitoring throughout the Great Lakes is important to enable scientists to relate current forage conditions to egg survival.  Secondary objectives of this spawn survey were to obtain relative estimates of lake trout spawner densities, determine the presence of naturally spawned lake trout, and to record sea lamprey wounding rates.         

Nearly 15,000 feet of gill-net was set during the survey period and biologists handled nearly 600 lake trout.  Ripe spawning females proved to be elusive and eggs from 8 females were collected for thiamin analysis. 

Spawner densities were relatively high at 41 lake trout per 1000’ of net fished.  Roughly 3% of the captured lake trout were not fin-clipped which suggests either they evaded marking at the hatchery or they were naturally spawned. 

The survey also resulted in recaptures of 165 coded wire tagged lake trout; these recaptures are important because fish strain, age, and stocking location can be obtained with the tags and  provides information on lake trout stocking success and fish movement.