An estimation of carrying capacity for sea otters along the California coast

Carrying capacity (K) for the California sea otter (Enhydra lutris nereis) was estimated as a product of the density of sea otters at equilibrium with in a portion of their existing range and the total area of available habita t. Equilibrium densities were determined using the number of sea otters obs erved during spring surveys in 1994, 1995, and 1996 in each of three habita t types where sea otters currently exist. Potential sea otter habitat was d efined as from the California coastline to the 40-m isobath and classified as rocky, sandy, or mixed habitat according to the amount of kelp and rocky substrate in the area. The amount of habitat available to sea otters in Ca lifornia was estimated using a Geographic Information Systems (GIS) program . The estimated mean number of sea otters that could be supported by the ma rine environment to a depth of 40 m in California was 15,941 (95% CI 13,538 -18,577). The GIS-based approach incorporated detailed bathymetric contours , produced repeatable and accurate estimates, and served as an innovative m ethod of measuring sea otter habitat. We believe the approach described in this paper represents the best available information on how a sea otter pop ulation at equilibrium would be distributed along the California coast.