Influence of Predation Mortality on Survival of Chinook Salmon Parr in a Lake Michigan Tributary

Abstract

Predation mortality among Chinook salmon Oncorhynchus tshawytscha parr can act at small spatiotemporal scales and cause variability in parr survival and potential recruitment. We analyzed predator diets and multiplied per capita consumption rates by predator population estimates to evaluate the relative effect of predation by stocked sport fishes on the variability in survival of Chinook salmon parr in the Muskegon River, Michigan, from 2004 to 2007. Brown trout Salmo trutta were a major predator of Chinook salmon parr, consuming from 15% to 34% of the total number available, while walleyes Sander vitreus consumed from 0.2% to 15%. Walleyes also consumed large quantities of brown trout and rainbow trout O. mykiss. Brown trout predation on Chinook salmon parr was largely dependent on parr size, while walleye predation was buffered by the availability of rainbow trout and brown trout. Predation mortality appeared to be responsible for a more than three-fold difference in the survival of Chinook salmon parr in the Muskegon River. The vulnerability of Chinook salmon parr to predation appeared to be controlled by parr growth rates, brown trout stocking dates, and the number of brown trout stocked. Fishery regulations to manipulate piscivore abundance may lead to higher survival and lower variability in the survival of Chinook salmon parr.

Received May 6, 2010; accepted November 30, 2010

ACKNOWLEDGMENTS

Funding for this study was provided by the School of Graduate Studies and the School of Natural Resources and Environment at the University of Michigan, the Great Lakes Fishery Trust (2001.71), the Saginaw Bay Walleye Club, and Trout Unlimited. We thank Lori Ivan, Dan Ruberg, Dennis Donahue, Steve Pothoven, John Hanson, Christine (Diana) Crissman, Ember Vannoy, and James Roberts for their assistance in the field; James Diana and Deborah Goldberg for manuscript edits; and NOAA's Great Lakes Environmental Research Laboratory for laboratory space. This is contribution number 2010–079 from the Great Lakes Environmental Research Laboratory.