Impacts of Sea Otter Recolonization on Marine Resources and Coastal Communities in Southern Southeast Alaska
University of Alaska Fairbanks
School of Fisheries and Ocean Sciences, University of Alaska Fairbanks
- Zachary Hoyt, PhD program
Please see The Southern Southeast Alaska Sea Otter Project website and Alaska Sea Grant News page for additional information.
This project continues the Alaska Sea Grant project launched in 2010 to investigate the impacts of sea otter recolonization on four commercially important species and their associated fisheries (southeast Alaska sea cucumbers, red sea urchins. Dungeness crab, and geoduck clams). This project will provide stakeholders, resource managers, and policy makers with information needed to consider the impacts of a marine mammal predator on commercially important fisheries.
Sea otter population growth, and predation on commercially important shellfish species, are of increasing concern to commercial fishermen in southeast Alaska. At a recent Alaska Board of Fisheries meeting, seven of sixteen Dungeness crab proposals represented attempts to close specific areas to commercial or sport fishing for shellfish species, as a response to predation by sea otters. The proposals indicate a contraction of the commercial shellfish harvest due to sea otter predation. Finding meaningful solutions to the problems this presents to commercial, sport, and subsistence users is difficult, if not impossible, without a good understanding of the extent and nature of sea otter use of these species. Long-term business planning for commercial and sport shellfish harvesters is more difficult when the future health of the stock is uncertain.
Why is this an Alaska Sea Grant project?
One of Alaska Sea Grant's six key goals outlined in the 2009–2013 Strategic Plan is sustained, well-managed, and healthy marine, coastal, and watershed ecosystems in Alaska. The program pursues this goal through support of research that provides decision-makers with science-based information that can be used to craft well-informed policies governing the use and conservation of Alaska's marine and coastal resources.
How will researchers conduct their study?
Researchers will survey diets of sea otters in areas identified as important to commercial fisheries. In addition we will investigate the diet of 40 sea otters, radio-tagged at the current sea otter population boundary as a part of a companion NPRB project. We hypothesize that the proportion of sea otter diet that is of commercial importance on the colonizing front of a population is greater than in areas where sea otters have occupied habitats for extended periods. Using data obtained through these efforts in combination with Alaska Department of Fish and Game catch and bioassessment statistics, researchers will quantify current effects and project future effects of sea otters on invertebrate fisheries in the region. They will examine historic sea otter distribution by collecting local and traditional knowledge through stakeholder interviews. They will then assimilate this information into a spatial model and present a draft of the model to stakeholders during outreach meetings in five communities in southern Southeast Alaska. At these meetings, researchers also will report findings and engage local communities in discussions about the effects of an increasing sea otter population on local fisheries. After completion of fieldwork and associated data analysis, they will conduct a one-day workshop with federal and state management agency personnel, stakeholders, tribal and community leaders, and outside experts on sea otter/fisheries conflicts to present results and discuss possible management actions for this continuing fisheries conflict.
U.S. Fish and Wildlife Service
Alaska Department of Fish and Game
Southeast Alaska Regional Dive Fisheries Association
Petersburg Marine Mammal Center
Petersburg Vessel Owners Association
United States Geological Survey and University of California Santa Cruz
What researchers learned
Sea otter forage data were collected from throughout southern Southeast Alaska in 2010, 2011, and 2012 to estimate the proportion of sea otter diet that is commercially important. In total, 6,117 foraging dives and 699 bouts (the sampling unit for analysis) were observed using high-powered telescopes. Data analysis is complete and a manuscript draft is currently being prepared.
We have concluded collecting movement data on 30 sea otters implanted with VHF transmitters near Kake, Alaska. The data have been analyzed and a draft manuscript has been prepared. Results show a strong sexual segregation of tagged individuals as well as a change in the distribution of otters in the Kake area from previous years. Tagged sea otters are no longer exploiting new areas beyond the range; rather the distribution of otters has contracted to areas in which sea otters have been present for many years. We conclude these changes may be due to increased hunting pressure in the Kake area.
Anticipated impacts: This project will provide resource managers with information needed to consider marine mammal predator impacts on commercially important fisheries. A proposed one-day otter management workshop will bring together federal and state management agency personnel, residents and stakeholders, tribal and community leaders, and outside experts on sea otter/fisheries conflicts to discuss results and possible management actions for this continuing fisheries conflict.
Results of this project will have direct application to the fishing industry. Long-term business planning for commercial and sport shellfish harvesters and processors will be informed by the results. The future status of commercially valuable marine invertebrate stocks is uncertain, and our project will provide valuable information on the potential outcome. In addition, stakeholders will have valuable data to help make predictions about future earnings in their fisheries or businesses. Information gathered and distributed in this project will allow stakeholders to lobby for management or legislative changes to address predicted declines in shellfish populations. Analysis of declines in commercial marine invertebrate fisheries during this project will inform that discussion. Finally, the inclusive process will increase understanding by shellfish users and the participating public of the biology of sea otters and their shellfish resources. Presentations of this work to the public will include explanations of life cycles, habitat, diet, and other basic information about the important role sea otters play in kelp forest ecosystems.
Anticipated outcomes: Researchers will use the combined collection of foraging data, studies of sea otter movement rates, historic sea otter distribution information, and local and traditional knowledge to analyze fishery impacts and create a spatial model of sea otter activities as a tool to inform long-term business planning for commercial and sport shellfish harvesters, as well as provide information for the future management of sea otters in southeast Alaska. Researchers also will reach out to coastal community residents and stakeholders through meetings and a sea otter management workshop.
A UAF graduate student will be involved in this project and a doctoral dissertation will result as well as peer reviewed manuscripts. Additional research elements include investigations of ecological changes caused by sea otters and trends in the sea otter movements and recolonization, if additional funds became available. Researchers expect a minimum of two manuscripts to result from this proposed study, with target journals including Marine Mammal Science and Ecological Applications. Further, they will present the results of this work at the fall 2012 Alaska Chapter of the American Fisheries Society and the 14th Sea Otter Workshop scheduled in March 2013.
Hoyt, Z.N. 2015. Resource competition, space use and forage ecology of sea otters, Enhydra lutris, in southern southeast Alaska. Ph.D. dissertation, University of Alaska Fairbanks, SGT-15-01, 152 pp.
Newsome, S.D., M.T. Tinker, V.A. Gill, Z.N. Hoyt, A. Doroff, L. Nichol, and J.L. Bodkin. 2015. The interaction of intraspecific competition and habitat on individual diet specialization: A near range-wide examination of sea otters. Oecologia 178(1):45-59. https://doi.org/10.1007/s00442-015-3223-8
Larson, S.D., Z.N. Hoyt, G.L. Eckert, and V.A. Gill. 2013. Impacts of sea otter (Enhydra lutris) predation on commercially important sea cucumbers (Parastichopus californicus) in southeast Alaska. Canadian Journal of Fisheries and Aquatic Sciences 70:1498-1507. https://doi.org/10.1139/cjfas-2013-0025