Gulf of Alaska | Ecosystem Perspectives DOCTORATE POSTER PRESENTATION Assessing the effects of sea otters on depth distributions of Dungeness crab in Southeast Alaska Presenter: Carter Johnson , cjjohnson22@alaska.edu, University of Alaska Fairbanks Sea otters ( Enhydra lutris ) consume large quantities of macroinvertebrate prey and have a well-documented history of disrupting fisheries throughout the North Pacific. The expansion of the sea otter population in Southeast Alaska from ~400 translocated individuals in the 1960s to over 25,000 individuals resulted in reductions to invertebrate fishery species, including sea cucumbers and sea urchins. However, the region continues to support a highly productive Dungeness crab ( Metacarcinus magister ) fishery, and it is unclear how this is possible. We are investigating the ecological conditions in Southeast Alaska that may allow commercial Dungeness crab catch to persist in proximity to sea otters. Here we test one hypothesis that Dungeness crab may utilize a depth refuge beyond the diving limits of sea otters to avoid predation. We set 130 crab pots at depths within and below the regular diving limits of sea otters in four bays in Southeast Alaska; two bays that were newly colonized by sea otters and two bays without sea otters. The depth distribution of Dungeness crab was similar among bays with and without sea otters, suggesting crabs are not shifting to deeper habitat. The presence of sea otters, however, was associated with a reduction in size of male Dungeness crab. Future studies could examine if crab seek a depth refuge in areas with long established sea otter populations. We plan to further investigate the spatial and temporal overlap of Dungeness crab and sea otters to better understand interactions between these two species. Jessica Whitney , jmwhitney2@alaska.edu, University of Alaska Southeast Emily Vernon , emilyvernon@u.boisestate.edu, Boise State University Ginny Eckert , gleckert@alaska.edu, University of Alaska Fairbanks
Alaska Marine Science Symposium 2023 157
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