Population Status Abstracts
Pending Publishing Permission
Southern sea otter status as indicated by recent surveys and strandings Julie Yee, USGS Western Ecological Research Center Full Abstract
The southern sea otter population has been counted each spring using the same methods since 1983. We use a three-year running average of the total number of sea otters counted in spring surveys along the mainland and at San Nicolas Island to derive the range-wide index of relative abundance, which is now 3128, down from 3186 in 2017. Regional trends vary, but the overall 5-year trend remains slightly positive in 2018. The sea otter's population range has remained unchanged for a decade. The effort to document all stranded southern sea otters continued. The number of beach-cast sea otter carcasses and live strandings in California continued at an elevated rate in 2018, with the per capita strandings over the last 3 years being above 14% (the number of strandings divided by the 3-year running average of the mainland spring count). Sea otter mortality from white shark bite also continued at high levels in 2018, especially near both ends of the range. This mortality is likely a significant factor in the lack of range expansion. |
Washington northern sea otters: population and causes of mortalities summary
Deanna Lynch, US Fish and Wildlife Service, Washington Fish and Wildlife Office Watch Video (Login required) Full Abstract
Northern sea otters (Enhdyra lutris kenyoni) were extirpated along much of the coast of North America by the early 1900s. During the 1960s and 1970s, otters from Alaska were reintroduced along the coasts of Oregon, Washington, and British Columbia. The minimum population estimate in Washington was approximately 2,058 sea otters in 2017, and this population continues to grow at approximately 9.5% per year. In 2017, approximately 80% of the population occured in a few large rafts within the 40-mile segment of the coast between the Quillayute River and Point Grenville. A centralized stranding response program for voluntary reports in Washington and Oregon began in 2002. Between 2017 and 2018, a total of 75 dead or moribund sea otters were reported, 74 in Washington and 1 in Oregon. Of these, 9 were live strandings, all of which subsequently died or were euthanized. Eleven carcasses that were fresh or moderately decomposed were shipped for necropsy to USGS’s National Wildlife Health Center. Of these11 cases, 7 deaths were attributed to protozoal meningoencephalitis due to Sarcocystis neurona, 2 were heart-related, and 2 were hepatic necrosis. |
A Bayesian model of Washington sea otter population dynamics
Jessica R. Hale, School of Aquatic and Fishery Sciences, University of Washington Watch Video (Login required) Full Abstract
The northern sea otter (Enhydra lutris kenyoni) was extirpated from Washington State in the early 1900s and reintroduced in 1969 and 1970. After their reintroduction, counts of sea otters were collected during coastal aerial and land-based sea otter surveys from 1977 to 2017 and were used to generate indices of population size. We used a Bayesian state space modeling framework to fit a model to the survey data, as this approach easily allows for both process error (reflecting environmental stochasticity) and uncertainty arising from observation error. The model tracks abundance and demographic processes within regions of the Washington coast. We will present preliminary results from this model. |
Pending Publishing Permission
Conservation success, now what? Challenges of maintaining long-term population surveys for a species with an expanding range. Linda Nichol, Fisheries and Oceans Canada (DFO) Full Abstract
Canada’s sea otter population, primarily descendants of a small number of animals (85) translocated from Alaska (1969 to 72), has continued to grow and its range expand, re-occupying historically occupied habitat. But where surveys were once easily accomplished in a period of a few days in the region where the population first established, the population now ranges over a broad area that challenges the current survey methods given the size of the area. Successful conservation, but how to maintain the population growth time series? This talk will discuss the challenges and considerations for ongoing monitoring of this conservation success story and future and emerging objectives for population surveys. |