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Annual California Sea Otter Census - 2015 Spring Census Summary

September 16, 2015

The spring 2015 mainland sea otter count began on 2 May and wasn't completed until 2 July. The delay in finishing the census was due primarily to limited availability of the survey plane (because of the need for the plane during the oil spill in the Refugio State Beach area). Overall viewing conditions this year were more favorable than those during the 2014 spring census (View Score = 2.6 vs. 2.3, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be about normal for this time of year. Sea otters along the mainland were surveyed (using a combination of ground-based and aerial-based surveys) from Pillar Point in San Mateo County in the north, to Rincon Point in the south at the Santa Barbara/Ventura County line. A separate ground-based survey of the sea otter population at San Nicolas Island was completed earlier (April 17-April 20). Surface kelp canopies at the time of survey were estimated to be below normal and survey viewing conditions were fair to good (View Score = 1.5). The population of sea otters at San Nicolas Island, the most remote of the Channel Islands in southern California, is the result of a translocation effort in 1987-1990 and remains geographically distinct from the mainland range; however, this population is no longer classified as an experimental population, and beginning in 2013 the San Nicolas counts have been added to the counts for the mainland range to arrive at a California-wide index of abundance. Detailed results from the annual survey are provided in the attached summary report.

Publication Year 2015
Title Annual California Sea Otter Census - 2015 Spring Census Summary
DOI 10.5066/F7F47M5C
Authors M. Tim Tinker, Brian B Hatfield
Product Type Data Release
Record Source USGS Digital Object Identifier Catalog
USGS Organization Western Ecological Research Center - Headquarters