• Diets, distribution and population dynamics of Arctic cod (Boreogadus saida) in Arctic shelf ecosystems

      Marsh, Jennifer M.; Mueter, Franz; Danielson, Seth; Iken, Katrin; Quinn, Terrance J. II (2019-05)
      With climate warming and longer open-water seasons in the Arctic, there is an increased interest in shipping, oil exploration and the expansion or development of commercial fisheries. Anticipated natural and anthropogenic changes are expected to alter the Arctic shelf ecosystems, including their fish communities. As a component of the Arctic Ecosystem Integrated Survey (Arctic Eis), this project presented a unique opportunity to assess the ontogenetic, spatial and temporal variability in the distribution, abundance and trophic roles (trophic level and diet sources) of key fish species in the Chukchi Sea. For my dissertation, I addressed three objectives to advance our understanding of Arctic cod (Boreogadus saida) as a key component of Arctic ecosystems. First, I characterized the current range of variability in trophic roles within the system and explored the role of advection in shaping the fish communities' diet (isotopic signatures) with a focus on Arctic cod. Second, I examined environmental and biological influences on the distribution and abundance of Arctic cod and provided an updated stock assessment for the Chukchi Sea. Finally, I broadened the geographic scope and used available time series of survey data at the southern margin of their range in the Pacific (eastern Bering Sea) and Atlantic (Newfoundland/Labrador shelves) sectors to assess the influence of temperature, predators and competitors on their distribution. Compared to age-1+ Arctic cod, age-0 Arctic cod had a less diverse diet regardless of water mass and were limited to colder temperatures. Together, this suggests that younger Arctic cod are more vulnerable to climate change. Estimates of egg production and early survival suggest that the numbers of mature Arctic cod present in the survey area during summer are unlikely to produce the observed high abundances of age-0 Arctic cod in the Chukchi Sea. Moreover, Arctic cod distributions in their southern ranges were highly influenced by temperature and to a lesser extent by competitors and predators. When temperatures were warmer, Arctic cod occupied a smaller area. These results inform the management of Arctic cod in a rapidly changing environment and provide benchmarks against which to assess future changes.
    • Regional distribution, life history, and morphometry of spawning stage Capelin Mallotus villosus

      Ressel, Kirsten N.; Sutton, Trent M.; Bell, Jenefer L.; Seitz, Andrew C. (2019-12)
      Capelin Mallotus villosus is a forage fish that is integral to many Arctic and subarctic marine food webs, but is less thoroughly studied outside the Atlantic Ocean. The goal of this research was to study spawning Capelin in data-poor areas, particularly in waters off the coast of Alaska and the western Canadian Arctic, to enrich baseline data and allude to intraspecies diversity. Chapter one examined the distribution and life history of spawning Capelin in Norton Sound, Alaska, by conducting aerial surveys, collecting sediment samples to characterize beach spawning habitats, and identifying biological attributes of spawners (e.g., body size, age, fecundity, etc.). Chapter two used a geometric morphometric approach (i.e., relative warps) and multiple statistical techniques (i.e., relative warp analysis, Procrustes analysis of variance, estimates of morphological disparity, and canonical variates analysis) to differentiate among and within putative populations of spawning Capelin in the western Canadian Arctic, Newfoundland, Canada, and Alaska. Spawning Capelin in Norton Sound portrayed similar behaviors, occupied similar beach habitats, and encompassed a similar range in biological attributes as fish observed in other regions throughout this species' geographic distribution. However, average spawner body size, age, fecundity, and morphometry differed among regions. These results suggest that Capelin exhibit some similarities in spawning behavior and habitat use across their geographic distribution, but may exhibit population-specific differences in biological attributes among and within regions.