Ontogenetic Shifts in Habitat and Diet of Cutthroat Trout in Lake Washington, Washington

Abstract

Salmonids often display a series of ontogenetic shifts in habitat, and these may also be associated with changes in diet. For example, adfluvial populations rear in streams for several years and then migrate to lakes. The patterns of habitat use, trophic ecology, and movements of such populations are commonly studied during the riverine stages. The lacustrine period is typically less well known, but salmonids may play an important ecological role as lake piscivores. In Lake Washington, Seattle, Washington, cutthroat trout Oncorhynchus clarki are a top native piscivore and may affect the dynamics of the fish and zooplankton upon which they prey. Our objective was to study the growth, diet, and size distribution of cutthroat trout in littoral and limnetic habitats of Lake Washington, with emphasis on consumption of two of the lake's dominant pelagic planktivores: juvenile sockeye salmon O. nerka and longfin smelt Spirinchus thaleichthys. Cutthroat trout entered the lake at approximately age 2. As they grew larger, the cutthroat trout became increasingly piscivorous and tended to occupy the limnetic zone after they reached about 250 mm fork length (FL). Specifically, percentages (by wet weight) of fish in the diet of cutthroat trout increased from 22.5% for cutthroat trout smaller than 200 mm FL to over 95% for cutthroat trout larger than 400 mm FL. Fish made up a higher percentage of cutthroat trout diets in fall and winter in both the limnetic and littoral zones, and a greater proportion of fish was consumed in the limnetic zone than in the littoral zone. Variation in diet was observed among years (1995–2000), apparently reflecting the relative abundance of longfin smelt. The role of cutthroat trout both as the object of recreational fisheries and as a predator on sockeye salmon (valued in commercial and recreational fisheries) complicates management of this large, urban lake.

Predation on native sculpin by exotic brown trout exceeds that by native cutthroat trout within a mountain watershed (Logan, UT, USA)

“…This lower piscivory cannot be attributed to a gape limitation, given that cutthroat trout have a similar length-gape relationship (Reimchen 1991). Rates of piscivory for cutthroat trout > 300 mm in lakes can exceed 50% (Cartwright et al 1998;Nowak et al 2004), but diet studies of large cutthroat in streams are rare. Rates of piscivory for cutthroat trout > 300 mm in lakes can exceed 50% (Cartwright et al 1998;Nowak et al 2004), but diet studies of large cutthroat in streams are rare.…”

Effects of Introduced Fishes on Wild Juvenile Coho Salmon in Three Shallow Pacific Northwest Lakes

“…During the late 19th and early 20th centuries, European settlers and the U.S. Most studies of interactions among introduced fishes and Pacific salmon have been conducted in large, deep lakes, reservoirs, or large river systems (Poe et al 1991;Tabor et al 1993;Fayram and Sibley 2000;Nowak et al 2004). The introductions and subsequent movement of these fishes were widespread, and virtually all lowland lakes and many river systems in the Pacific Northwest region of the United States now contain some introduced fishes.…”

Diel vertical movements, and effects of infection by the cestode Schistocephalus solidus on daytime proximity of three-spined sticklebacks Gasterosteus aculeatus to the surface of a large Alaskan lake

“…and char Salvelinus spp. ; Reimchen and Douglas 1984;Nowak et al 2004;Denton et al 2010). Sticklebacks and S. solidus have become a model system for understanding the ways in which a parasite can affect its host (Heins and Baker 2008), and many studies have compared the behavior of sticklebacks with and without parasites in controlled, laboratory environments (Giles 1983(Giles , 1987Milinski 1985;Barber and Huntingford 1995;Ness and Foster 1999;Barber et al 2004Barber et al , 2008Barber and Scharsack 2010).…”