The utilization of a Pacific salmon Oncorhynchus nerka subsidy by three populations of charr Salvelinus spp.

Abstract

The L(F) -at-age trajectories differentiated two populations of Dolly Varden charr Salvelinus malma and a population of Arctic charr Salvelinus alpinus from the eastern end of Iliamna Lake, Alaska. Salvelinus malma from the Pedro Bay ponds were the smallest for a given age, followed by Salvelinus alpinus from the lake, and S. malma from the Iliamna River were much larger. The utilization of a large sockeye salmon Oncorhynchus nerka subsidy by the three Salvelinus spp. populations was then investigated by comparing diet data and mixing model (MixSIR) outputs based on carbon and nitrogen stable isotopes. Stomach contents indicated that both S. malma populations fed on O. nerka products, especially eggs and larval Diptera that had scavenged O. nerka carcasses, whereas S. alpinus fed on a variety of prey items such as three-spined sticklebacks Gasterosteus aculeatus and snails. Stable-isotope analysis corroborated the diet data; the two S. malma populations incorporated more O. nerka-derived nutrients into their tissues than did S. alpinus from the lake, although all populations showed substantial utilization of O. nerka-derived resources. Salvelinus alpinus also seemed to be much more omnivorous, as shown by stable-isotope mixing models, than the S. malma populations. The dramatic differences in growth rate between the two S. malma populations, despite similar trophic patterns, indicate that other important genetic or environmental factors affect their life history, including proximate temperature controls and ultimate predation pressures.

Stable isotope evidence indicates the incorporation into Japanese catchments of marine‐derived nutrients transported by spawning Pacific Salmon

“…Resident salmonids often feed upon salmon eggs and carcass material when available (e.g. Reed, ; Bilby et al ., ; Denton et al ., ). This diet shift was associated with an increase in the condition factor of Dolly Varden in the Rusha River, as has been seen elsewhere in juvenile coho salmon ( O. kisutch ) and rainbow trout ( O. mykiss ) (Bilby et al ., ).…”

Evidence for genetic distinction among sympatric ecotypes of Arctic char (Salvelinus alpinus) in south‐western Alaskan lakes

“…The relatively low F ST values between Iliamna Lake and Lake Aleknagik suggest that gene flow has occurred recently between them or is ongoing, although Arctic char in both lakes are generally regarded as nonanadromous populations because they are present in the watersheds throughout the summer when anadromous char are typically in the sea and, at least in Iliamna Lake, diet comparisons inferred from stable isotopes do not support anadromous behaviour of Arctic char (Denton et al. ). Anadromy, however, could exist as an alternative, but less common life‐history strategy in these systems (e.g., McBride ); otolith microchemistry analysis of Arctic char from these lakes would provide a definitive test of this idea.…”

Resource polymorphism and diversity of Arctic charrSalvelinus alpinusin a series of isolated lakes

“…are present. In these systems, S. alpinus tend to be large‐bodied and piscivorous (Russell, 1980; Denton et al ., 2010). Even within the limited studies of more remote regions, however, life histories of S. alpinus and Dolly Varden Salvelinus malma (Walbaum 1792) can vary substantially (Russell, 1980; Denton et al ., 2010; Jaecks, 2010).…”