Although steelhead (Oncorhynchus mykiss) is a culturally and recreational important species throughout North America, less is known about its ocean than its freshwater ecology. To provide insights into migratory routes and habitats occupied by steelhead in the North Pacific Ocean, we attached pop-up satellite archival tags (PSATs) to female steelhead kelts from three watersheds on the east coast of Prince of Wales Island, in southern southeast Alaska. PSATs successfully recorded extensive westward post-spawning migrations of nine female kelts across the Gulf of Alaska to areas near the Alaska Peninsula and Aleutian Islands. From the months of June to October, tagged steelhead occasionally dived to 10–20 m, but spent approximately 90

Piscivorous groundfish have been implicated as a major hindrance to Pacific herring (Clupea pallasii) population recovery within Prince William Sound, Alaska (PWS); however, the key piscivores have not been identified. To address this knowledge gap, groundfish were collected from PWS herring nursery fjords (2009–2012) during winter, a period when juvenile herring energy levels decrease, suppressing predator avoidance. Three species, Pacific cod (Gadus macrocephalus), walleye pollock (G. chalcogrammus), and big skate (Beringraja binoculata) were identified as key herring consumers based on diet frequency of occurrence. Their stomach contents were examined to document any variability in prey occurrences and to explore whether pollock or other prey types could mediate herring consumption. For Pacific cod, there was strong evidence of seasonality in herring consumption, with herring occurring in 7% and 50% of stomachs in November and March, respectively. Walleye pollock and big skate diets were more influenced by body size and longitude, respectively. Pacific cod consumed notably more adult herring (ages 3+) than the other piscivores, big skate consumed herring ages 3+ and younger, while walleye pollock was a major consumer of age 0 herring. As groundfish body size increased, all three species consumed larger, age 2+ pollock, suggesting pollock presence mediates herring overwintering mortality and that pollock cannibalism is an important dietary pathway in PWS. By identifying the key groundfish consumers of herring and pollock in PWS, and the spatial, temporal, and biological variables that influence the occurrence of these forage fishes in their diets, this research contributes to a larger body of knowledge seeking to explain the mechanisms responsible for their lack of recovery in PWS and offers novel insight into the importance of pollock as a forage fish in PWS.

The contents of 1056 stomachs were included in a trophic-guild analysis to document separation amongst 16 groundfish species inhabiting Pacific herring Clupea pallasii and walleye pollock Gadus chalcogrammus nursery fjords in Prince William Sound, Alaska and to determine the relative contribution of C. pallasii and G. chalcogrammus to that separation. A total of five multi-species feeding guilds and one outlier species were determined through multivariate analyses. Major gradients of trophic separation spanned from invertebrates (mostly shrimps, crabs and unidentified decapods) to fishes (mostly unidentified fishes, C. pallasii and G. chalcogrammus) a pattern that was influenced by intra and interspecific differences in predator lengths. While C. pallasii and G. chalcogrammus were important to the overall guild structure, within-guild similarities were consistently highest due to unidentified fishes. In general, larger predators consumed the largest C. pallasii and G. chalcogrammus, with the smaller-on-average predators consuming smaller C. pallasii and fewer or smaller G. chalcogrammus. Regardless of guild inclusion, groundfishes primarily consumed pre-recruit C. pallasii and G. chalcogrammus (i.e., younger than age 3 years fishes), which has the potential to negatively influence recruitment of these forage fishes to the adult, spawning population.

Arctic staghorn sculpin (Gymnocanthus tricuspis) and shorthorn sculpin (Myoxocephalus scorpius) belong to Cottidae, the second most abundant fish family in the western Arctic. Although considered important in food webs, little is known about their food habits throughout this region. To address this knowledge gap, we examined and compared the diets of 515 Arctic staghorn sculpin and 422 shorthorn sculpin using stomachs collected over three summers in the northeastern Chukchi Sea (2010–2012) and one summer in the western Beaufort Sea (2011). We used permutational multivariate analysis of variance (PERMANOVA) and non-metric multidimensional scaling (nMDS) to compare sculpin diets between regions and selected size classes. Differences in mouth morphologies and predator size versus prey size relationships were examined using regression techniques. Arctic staghorn sculpin and shorthorn sculpin diet compositions differed greatly throughout the Chukchi and Beaufort Seas. Regardless of body size, the smaller-mouthed Arctic staghorn sculpin consumed mostly benthic amphipods and polychaetes, whereas the larger-mouthed shorthorn sculpin shifted from a diet composed of benthic and pelagic macroinvertebrates as smaller individuals to shrimps and fish prey as larger individuals. Within shared habitats, the sculpins appear to partition prey, either by taxa or size, in a manner that suggests no substantial overlap occurs between species. This study increases knowledge of sculpin feeding ecology in the western Arctic and offers regional, quantitative diet information that could support current and future food web modeling efforts.

Polar cod (Boreogadus saida) is an important link between top predators and lower trophic levels in high-latitude marine ecosystems. Previous findings describe differences in its diet throughout the western Arctic; however, the causes of this variation are not well known. This study examined the diets of juvenile polar cod collected via demersal trawling methods over three summers in the northeastern Chukchi Sea (2010–2012) and one summer in the western Beaufort Sea (2011) to determine the amount of variability explained by biological, spatial, and interannual factors. Prey were identified, measured for length, and aggregated by percent mean weight into taxonomically coarse prey categories for analysis. Within seas, variation in juvenile polar cod diet composition was significantly related to body size, latitude, longitude, depth, and interannual (Chukchi Sea only) factors. Canonical correspondence analysis indicated body size was the most important factor contributing to the total variance in juvenile polar cod diet in the Chukchi and Beaufort Seas. Body size-based diet differences between the Chukchi and Beaufort Seas were evaluated using non-metric multidimensional scaling. This method revealed that similar-sized polar cod consumed similar-sized prey in both seas, but their diets were more benthically influenced in the Chukchi Sea and more pelagically influenced in the Beaufort Sea. Juvenile polar cod diet compositions vary by body size and region of inhabitance throughout their distribution. Here, we show that body size was the primary factor explaining variation in the summer diet of juvenile polar cod within the Chukchi and Beaufort Seas.

Diet information for Arctic Cod (Boreogadus saida), Arctic Staghorn Sculpin (Gymnocanthus tricuspis), and Shorthorn Sculpin (Myoxocephalus scorpius) in the northeastern Chukchi and western Beaufort seas is mostly descriptive. In this study, I examined diet variability due to region, depth, and body size by quantitatively comparing these fishes’ diet compositions. To accomplish this, I analyzed the stomach contents of 1,620 fishes collected over three summers in the northeastern Chukchi Sea (2010-2012) and one summer in the western Beaufort Sea (2011). In general, body size and region accounted for most differences in diets. As body size increased, each species consumed a more varied diet composed of larger prey. Additionally, each species consumed more benthic prey taxa in the northeastern Chukchi Sea than in the western Beaufort Sea. These findings indicate that a combination of both body size and region-specific oceanographic processes are likely driving the observed variability in these species’ diets. Documenting this variability provides a better insight into the present relationships between these fishes and their prey over a large area and offers a benchmark for future diet analyses in the western Arctic.