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Marine Ecology Progress Series

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MEPS 655:123-137 (2020)  -  DOI:

Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries

Tracy M. Grimes1,*, M. Tim Tinker2, Brent B. Hughes3, Katharyn E. Boyer4, Lisa Needles5, Kathryn Beheshti2, Rebecca L. Lewison1

1Department of Biology, San Diego State University, San Diego, CA 92182, USA
2Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA
3Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
4Estuary & Ocean Science Center, San Francisco State University, Tiburon, CA 94920, USA
5Center for Coastal Marine Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA
*Corresponding author:

ABSTRACT: Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

KEY WORDS: Enhydra lutris · Dungeness crab · Species recovery · Predation · Foraging ecology

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Cite this article as: Grimes TM, Tinker MT, Hughes BB, Boyer KE, Needles L, Beheshti K, Lewison RL (2020) Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries. Mar Ecol Prog Ser 655:123-137.

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