A Biological Assessment of the Warmwater Fish Community in Lake Washington

The limnology of Lake Washington has been studied extensively over the past 100 years, and many changes have occurred during that time that have dramatically altered the fish community and fish habitat.  In the past two decades, researchers at the University of Washington and U. S. Fish and Wildlife Service have conducted many research projects that broadened our understanding of food web dynamics, trophic relationships, and impacts of predatory fishes on outmigrating salmonids.  Although extensive sampling accompanied these research projects, a whole-lake assessment of the warmwater fish community has never been conducted. 

To update our knowledge of the warmwater fish community and draw comparisons to prior sampling, we conducted a "standardized warmwater survey" developed by the Warmwater Program (Washington Department of Fish and Wildlife) in 1997.  Using electrofishing, gill netting, and fyke netting, we sampled a total of 248 locations and captured 40,894 individuals representing 22 species.  Warmwater gamefish comprised 73.7% of the sample by number, but only 33.7% of the sample weight.  Collectively, coldwater gamefish species including Northern Pikeminnow Ptychocheilus oregonensis, Peamouth Chub Mylocheilus caurinus, and Largescale Suckers Catostomus macrocheilus accounted for 50.1% of the biomass.  Threespine Stickleback Gasterosteus aculeatus was by far the most abundant species comprising 70% of the sample by number.  Yellow Perch Perca flavescens was the most abundant warmwater gamefish species sampled and comprised 19% of the sampled biomass; second to Largescale Suckers (35.3%).  Pumpkinseed Lepomis gibbosus was the second most abundant warmwater gamefish, followed by Brown Bullhead Ameiurus nebulosus and Smallmouth Bass Micropterus dolomieu.  Other gamefish including Rainbow Trout Oncorhynchus mykiss, Coastal Cutthroat Trout Oncorhynchus clarkii clarkii, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus salmoides, and Black Crappie Pomoxis nigromaculatus constituted a small portion of the sample.  These results suggest that, similar to other Washington lakes, the fish community of Lake Washington is dominated by "coolwater" species that include Yellow Perch, Pumpkinseed, Smallmouth Bass, and Brown Bullhead Catfish.  Comparisons to 1982 sampling suggest that Largemouth Bass and Black Crappie have declined in relative abundance over the past 30 years, while the relative abundance of Smallmouth Bass has increased.