**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract for this completion report are provided below. For a copy of the full completion report, please contact the author via e-mail at dobieszn@msu.edu or via telephone at 517-355-0126. Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

UNDERSTANDING CHANGING PATTERNS OF SIZE-SPECIFIC MARKING OF LAKE TROUT BY SEA LAMPREY

N.E. Dobiesz¹, J.R. Bence¹

¹ Quantitative Fisheries Center, Michigan State University, East Lansing, MI

May 2015

ABSTRACT:

Parasitic, non-native sea lamprey cause wounds on Great Lakes fish, increasing their mortality rates. Of particular importance to fisheries managers is the negative impact this mortality has on lake trout restoration efforts. Sea lamprey-induced mortality has been found to correlate with the frequency of sea lamprey marks per fish. In this study we found that marking rates increased asymptotically in a general logistic shape, but showed substantial variation in overall marking rate and inflection point of the relationship both spatially and temporally. Because foraging theory suggests that predation may favor larger hosts, we also examined how lake trout abundance may influence wounding rates. The results suggest that large lake trout abundance, by itself, is not a strong predictor of spatial differences and temporal trends of sea lamprey size-selectivity. Finally, we examined whether season, lake trout strain, or depth of collection influences sea lamprey marking rates on lake trout. While some general trends were evident, such as the lowest wounding rates occurring in the summer across all lakes, and higher wounding rates on Great Lakes origin and Finger Lakes origin strains over other strains, common patterns of wounding rates were not found for these factors and many did not appear to be influenced by lake trout size.