Diet and Selection of Major Prey Species by Lake Michigan Salmonines, 1973–1982

Abstract

To elucidate prey preferences, we quantified stomach contents of 1,231 salmonines collected from inshore (21 m or shallower) southeastern Lake Michigan during 1973–1982. Predators ate 12 species of fish. Alewife Alosa pseudoharengus made up 48–79% by weight of the diet of brown trout Salmo trutta, chinook salmon Oncorhynchus tshawytscha, coho salmon Oncorhynchus kisutch, lake trout Salvelinus namaycush, and rainbow trout Salmo gairdneri. Alewives eaten ranged from 23 to 245 mm total length; 46% were 150–200 mm. Rainbow smelt Osmerus mordax eaten were 21–245 mm long and made up 4–11% of the salmoninesˈ prey. There were significant direct linear relationships between lengths of alewives and rainbow smelt eaten and lengths of the five predators. Alewives are currently declining in Lake Michigan. If their population collapses, there should be a shift to alternative prey species. We have seen no such shift through 1982, although more recent data of other investigators show a decline in the importance of alewife in salmonine diets. Diets of the midwater‐feeding chinook and coho salmon were heavily dominated by the pelagic alewife, whereas brown and lake trout diets were more diverse. This suggests that trout should have better survival and growth than salmon, because trout would be able to utilize the more benthic yellow perch, Perca flavescens, rainbow smelt, and, to some degree, bloater Coregonus hoyi. The latter species are becoming more abundant with the decline in alewife. Under the current salmonine stocking regime, alewives will continue to supply a lower and variable portion of the salmonine diet, and predatory pressure on alewife should lead to increases in endemic prey speciesˈ populations.

Long‐term changes in legacy trace organic contaminants and mercury in Lake Ontario salmon in relation to source controls, trophodynamics, and climatic variability

“…Trophodynamic links-In the Great Lakes, coho and chinook salmon aged 2 yr and older feed almost exclusively on alewife (Alosa pseudoharengus) and most selectively on the largest individuals (Stewart et al 1981;Jude et al 1987;Jones et al 1993). Because predatory fish incorporate contaminants mostly from their food (Borgmann and Whittle 1991), we hypothesized that temporal variations in contaminant burdens would be a function of alewife population dynamics.…”

Chinook Salmon Foraging Patterns in a Changing Lake Michigan

“…Additionally, selectivity for Alewife has remained significant for both size-classes of Chinook Salmon despite high variation and overall reduction in Alewife prey abundance. Though it has been well documented that Alewife is the primary forage species for Chinook Salmon in the Great Lakes (Jude et al 1987;Stewart and Ibarra 1991;Rybicki and Clapp 1996;Warner et al 2008), the increase in importance of this item to the further exclusion of other prey items has appeared to result in almost complete diet dependence on Alewife.…”

“…A posteriori observation of the Alewife prey length versus Chinook Salmon predator length data suggested a nonlinear, asymptotic relationship with potentially significant differences in prey size maxima between time periods. Though simple linear regression has been used in previous studies for prey length versus predator length relationships (Jude et al 1987), we determined a nonlinear approach was more appropriate given our data. We used a backward stepwise regression approach using the initial model,…”

“…Despite indications that native Chinook Salmon populations in the Pacific Ocean are generalist predators (Hunt et al 1999), evidence suggests that naturalized Chinook Salmon in Lake Michigan are strongly selective for Alewife, select against Bloater and Rainbow Smelt, and fail to significantly alter foraging preference with changes in prey abundance (Stewart et al 1981;Jude et al 1987). Similarly, Warner et al (2008) found strong Chinook Salmon preference for Alewife above Bloater and Rainbow Smelt, but they also found that with increasing abundance of small Alewives, age-1 Chinook Salmon exhibited increasing preference for small Alewives and decreasing preference for large Alewives.…”

Regime alimentaire et croissance de la ouananiche (Salmo salar L ) du Lac St-Jean

“…Les données du régime alimentaire en 1989 n'a pas démontré de différence significative avec les données de Mahy (1976) en 1972 mais ont différé de celles de Desjardins (1989) Plusieurs auteurs ont démontré que les poissons fourrages et plus particulièrement l'éperlan (Osmerus mordax) étaient importants pour la croissance de la ouananiche (Lackey 1969;Havey 1973;Kircheis et Stanley 1981;Jude et al 1987). En pisciculture la croissance en longueur mais aussi l'état d'embonpoint des poissons sont influencés par la composition de la diète (Barrow et ai.…”