Informing sea otter reintroduction through habitat and human interaction assessment

MT Tinker,LG Torres,DV Kone

doi:10.3354/esr01101

Abstract

Sea otters Enhydra lutris have been absent from Oregon, USA, following their extirpation over a century ago. Stakeholder groups and native tribes are advocating for reintroduction to restore historic populations. We investigated the potential for successful reintroduction by: (1) estimating expected equilibrium sea otter densities as a function of habitat variables to assess sea otter habitat in Oregon; and (2) spatially relating areas of high expected densities to human activities (e.g. fisheries, recreation, vessel activity, protected areas) to anticipate potential disturbance or fishery resource competition. We estimated that 4538 (1742-8976; 95% CI) sea otters could exist in Oregon, with higher expected abundance (N = 1551) and densities (x̄ = 2.45 km-2) within the southern region. Most core habitat areas (97%), representing clusters of high expected densities, overlapped with some form of human activity. While commercial shipping and tow lanes overlapped little (1%) with core habitat areas, recreational activities (58%) and fisheries (76%) had a higher degree of overlap, posing higher disturbance risk. We anticipate higher resource competition potential with the commercial red sea urchin fishery (67% of harvest areas) than the commercial Dungeness crab fishery (9% of high-catch crabbing grounds). Our study presents the first published carrying capacity estimate for sea otters in Oregon and can provide population recovery targets, focus attention on ecological and socioeconomic considerations, and help to inform a recovery plan for a resident sea otter population. Our findings suggest current available habitat may be sufficient to support a sea otter population, but resource managers may need to further investigate and consider whether current human activities might conflict with reestablishment in Oregon, if plans for a reintroduction continue.

Highlights

Throughout history, humans have exploited wildlife populations, and these activities may partially explain Earth’s sixth mass extinction (Barnosky et al 2011, Dirzo et al 2014)
While we show sea otters may interact with people across the entire Oregon coast, we show some areas of more limited interaction potential where these negative interactions may be limited
Our study directly addressed those concerns by assessing potential interactions between sea otters, based on core habitat area distribution, and the Dungeness crab and red sea urchin commercial fisheries in Oregon

Summary

Introduction

Throughout history, humans have exploited wildlife populations, and these activities may partially explain Earth’s sixth mass extinction (Barnosky et al 2011, Dirzo et al 2014). As biodiversity loss has accelerated, the importance of species diversity to ecosystem function, resilience, and services has become apparent (Cardinale et al 2002, Elmqvist et al 2003, Downing & Leibold 2010). Biodiversity loss represents a prominent threat to environmental. Recovery of at-risk species, species vital to ecosystem function, can help maintain ecosystem integrity (Soulé et al 2003). Environmental managers enlist a range of strategies to facilitate at-risk species recovery, such as establishing protected areas, moving threatened populations into captivity, or conducting reintroductions and reinforcements (Briggs 2009)

Methods

Findings

Discussion

Conclusion