Ontogenetic Diet Shifts of Prickly Sculpin in the Lake Washington Basin, Washington

Abstract

We studied the ontogenetic diet shifts of prickly sculpin Cottus asper (the largest North American freshwater cottid) in the Lake Washington basin from a variety of habitat types, including fluvial and lacustrine. In all habitats, prickly sculpin progressively shifted to larger prey, such as fish and crayfish (Decapoda), as they increased in size. In offshore areas of Lake Washington, amphipods were the dominant prey by weight consumed by prickly sculpin of 75-124 mm total length (TL). Although generally uncommon numerically in the diet, fish (primarily small cottids) made up a large percentage of the diet by weight for prickly sculpin larger than 125 mm TL. In the lower end of the Cedar River, juvenile sockeye salmon Oncorhynchus nerka (23-30 mm TL) were most commonly observed in the diets of 50-99-mm prickly sculpin, while larger prickly sculpin tended to consume larger fish, including adult longfin smelt Spirinchus thaleichthys, lampreys Lampetra spp. (ammocoetes and adults), and small cottids. For each habitat type, diet overlap tended to decrease as size-classes became more dissimilar. Overall, the size of fish eaten was strongly related to prickly sculpin size, but the type of fish eaten influenced the relationship between prey size and predator size. The higher percentage contribution of fish to prickly sculpin diets seen here relative to other studies can be explained by the fact that (1) we collected many large prickly sculpin and sampled a wide variety of habitat types and (2) potential prey fish in the Lake Washington system are abundant and diverse. Our results, in combination with other research on the Lake Washington ecosystem, suggest that because of their size, abundance, wide range in habitat use, and breadth of diet, prickly sculpin are an especially important species in the food web of this system. Prickly sculpin are directly linked to the pelagic food web as both predators and prey, and they play a key role as benthic predators.

Assessment of Introduced Prickly Sculpin Populations in Mountain Lakes in Two Areas of Western Washington State

“…Prickly sculpin have been described as an opportunistic predator (Bond 1963, Tabor et al 2007c. Our results appear to be consistent with this characterization.…”

“…For age and diet analysis, fish were sampled from each of four size classes: 1) 50-74 mm, 2) 75-99 mm, 3) 100-124 mm, and 4) ≥ 125 mm TL that corresponded to earlier sampling in Lake Washington (Tabor et al 2007c). For diet analysis, fish were also sampled by depth (1, 5, and 10 m).…”

“…Freshwater sculpins primarily consume benthic macroinvertebrates but in some situations can be a predator of fish eggs (Foote and Brown 1998) or small fishes (Hunter 1959, Moyle 1977, Tabor et al 2007c). Simultaneously, sculpins are an important forage fish for stream- (Lowry 1966) and lake-dwelling piscivorous fishes (Ricker 1960, Elrod and O'Gorman 1991, Tabor et al 2007a) and other piscivores (Toweill 1974, Edgehouse et al 2013.…”

“…Although it is unclear how they were introduced (likely either as bait from anglers or accidentally introduced during trout stockings) and how long they have been in these lakes, individuals were observed by anglers as early as 1990. We hypothesized that because prickly sculpin are large (maximum > 230 mm total length, Tabor et al 2007b) relative to other sculpin species, they have the potential to consume a broader range of prey (Tabor et al 2007c) and therefore may cause a variety of ecological impacts in mountain lake ecosystems. In this study, we documented the presence of prickly sculpin in six mountain lakes and report fundamental ecological data (distribution, size, diet, age, and growth) that could be compared to existing information on native populations and help evaluate their potential to inhabit other mountain lakes.…”

Barriers to upstream passage by two migratory sculpins, prickly sculpin (Cottus asper) and coastrange sculpin (Cottus aleuticus), in northern Puget Sound lowland streams

“…Sculpins primarily eat benthic organisms and can structure the benthic community by selectively feeding upon locally abundant populations of macroinvertebrates (Bond 1963;Moyle 1976;Tabor et al 2007). In turn, they are prey for piscivorous fish and can be an important food source for juvenile salmon and trout (Moyle 1976; Tabor et al 2007). In Baker Lake, Canada, prickly sculpin larvae composed 39% of the stomach volume of juvenile sockeye salmon (Oncorhynchus nerka) (Heard 1965).…”