UW Aquatic & Fishery Sciences Quantitative Seminar
NOAA Northwest Fisheries Science Center
Using stable isotopes to assess potential sea lamprey damage to Lake Superior fishes
Accurate diet information has been unavailable for invasive sea lamprey (Petromyzon marinus) in the Great Lakes, which leads to oversimplified impact assessment. We examined stable isotope ratios of sea lamprey in six regions of Lake Superior in order to generate quantitative diet and host mortality estimates. According to two equilibrium mixing model techniques, top predators such as lake trout (Salvelinus namaycush) comprised 60-90% of sea lamprey diet in all areas except Black Bay, Ontario, where lake whitefish (Coregonus clupeaformis) and catostomids were the major hosts. We integrated stable isotope data and sea lamprey growth data into an individual-based sea lamprey feeding model and generated host-specific estimates of blood loss and mortality. Coregonines accounted for the majority of host deaths. Fewer lake trout deaths occurred, relative to a traditional impact model in which lake trout were the only hosts. In this diverse host assemblage, sea lamprey have more complex community-level effects than portrayed in current impact models.