The Great Lakes - St.Lawrence Research Inventory

In the project, we will develop models of size selective due to sea lamprey predation, gillnet harvest and trapnet harvast for the two species. We will intergrate these models into a life history model to predict optimal maturation scheduling. We will also develop a statistical model to describe maturation schedules of lake whitefish and simulate how the mortality-induced adaptive changes in life history traits influence fish population dynamics using a eco-genetic model.

Great Lakes food webs have changed dramatically since the establishment of dreissenid mussels, highlighted by large declines in Diporeia abundance. Recent work has linked lake whitefish growth declines in South Bay, Lake Huron to change in the benthic invertebrate community, where whitefish were distributed more nearshore and diets were dominated by energy-poor nearshore prey following dreissenid invasion. In contrast, anecdotal reports from commercial fishermen suggest that whitefish in Lake Huron?s main basin have moved deeper.

Recent changes in Lake Huron?s food web have led to a major change in pelagic-benthic coupling that had not been seen previously in Lakes Huron, Michigan, and Ontario. With the previous pelagic- benthic coupling, there were both pelagic and benthic energy pathways leading to pelagic forage fishes, and both Chinook salmon and lake trout fed on pelagic prey such as alewives and rainbow smelt. The new and current pelagic-benthic coupling is a contrast to the previous one because of the direct involvement and reliance on large bodied fish at top trophic levels of the food web.

RATIONALE: About 9 % of the lake trout in Lake Superior are siscowets, a deepwater morphotype and the main keystone predator. Despite their importance, their spawning locations have not been characterized. In 2 9 a high-resolution bathymetry/seabed classification map for a likely spawning area near Marquette was produced (funded by MN Sea Grant).We will follow-up with this project to locate where eggs are deposited and characterize the physical habitat. Because L.

Quantitative fishery stock assessment is an essential part of fishery management. Great Lakes Fishery Commission?s convention call for ??programs designed to determine the need for measures to make possible the maximum sustained productivity of any stock of fish??. Assessments modeling is essential to this and forms the basis for many specific policy evaluations. The sophistication of approaches has continued to advance, increasing the needed level of expertise to conduct assessments. Needed expertise is in short supply world-wide and in the Great Lakes.

Whether lake and stream ecotypes of brook trout in Lake Superior result from genetic polymorphism or phenotypic plasticity remains unexplored, but has important implications for the conservation and restoration of the declining lake (coaster) ecotype. We will test the hypotheses that individual differences in early behavior of brook trout from polymorphic populations are heritable and that the behavioral differences are linked to allelic variation and differential expression in candidate genes for behaviors that could be linked with migration.

The Great Lakes have been warming. In Lake Erie?s basin, cu¬mulative annual days with air temperatures < °C decreased by .54 d/yr (1956-2 7) and the mean minimum air temperature increased by .23°C/yr (1977-2 7). Increases of 3 to 8°C during winter are expected by 2 7 -2 99 across the Great Lakes, depending on the CO2-emission scenario. These changes, in turn, may be driving recruitment variability in economically and ecologically important fishes.

Egg thiamine data is used by managers to assess the risk of Thiamine Deficiency Complex (TDC; also known as EMS or Early Mortality Syndrome) in lake trout. Mean egg thiamine levels are currently measured in a pooled sample of 1 to 12 eggs per female, and the variability in thiamine among individual eggs within a clutch has not been characterized. Our objectives are to: 1) Determine how female lake trout allocate thiamine among individual eggs; 2.