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Page 3 of 3
  Diaptomus and Epischura are genera of calanoid copepods, present in the lake year-round. The population peaks occur in early spring (March and April) and again in late summer (August and September). In contrast, Daphnia peak abundances are generally in May and June. The role of the copepods in the food chain of Lake Washington is now being investigated, because of recent declines in sockeye fry and smolts. Before the increase of Daphnia in the mid 1970s, Epischura and a summer cladoceran, Diaphanosoma, had been the preferred prey of planktivorous fish in the lake.
Many fish species have been introduced into lakes of the United States, in part by the deliberate actions of the U.S. Bureau of Fisheries in the late 1800s. Some introductions in Lake Washington occurred just after the 1909 Alaska-Yukon Expedition, when fish dumped in Drumheller Fountain on the UW campus somehow found their way into the lake. Such introductions have often resulted in reducing native species through predation, competition, or other interactions. Lake Washington is known to have at least 28 fish species. Examples of introduced species in Lake Washington are large mouth bass, small mouth bass, black crappie, yellow perch, sunfish, brown bullhead (a type of catfish), goldfish, carp, and Atlantic salmon. While a native species such as the northern squawfish often takes the blame for being a voracious fish predator (the state has a bounty program for squawfish in certain areas), it may often be the introduced species that are causing the greatest impacts.
Rainbow trout are native to this area, but only two lakes (Ross Lake and Chester Morse Reservoir) in the state have self-sustaining populations; others are supplemented by hatcheries. The level of stocking in Lake Washington could have significant impact becasue of the trout predation on smelt, Daphnia, and sockeye fry. Crayfish and sculpins are very abundant in many parts of the lake and comprise a significant portion of the diet of several fish predators. Their abundance plays a big role in the lake ecology by acting as a buffer to predation on other species.
The Lake Washington story is an epic in the scientific literature, thanks to Dr. Edmondson and his contingent of students and researchers. His research went well beyond Lake Washington. The literature produced through his UW lab covered five decades, and the influences in science and lake management are enormous. Well known for his work in the Pacific NW, he was also an expert on rotifers (a group of invertebrates, mostly fresh water, with nearly 2,000 species), with publications going back to 1934. Much of the information in this section is garnered from Dr. Edmondson's work. For more information, see the following publication.
Edmondson, W.T. 1991. The uses of Ecology: Lake Washington and Beyond. University of Washington Press.
Sally Abella and Arni Litt, retired co-workers in the UW Zoology Department, kindly reviewed a draft of this section. Sally Abella currently works with the King County Small Lakes program.
Text written by Kevin Li
<<Page 2 of 3, The Lake Washington Story
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