The spring 2008 sea otter count began on 2 May and was completed on 24 May. Overall viewing conditions for this survey, 2.4, were slightly less favorable than those during the spring 2007 survey (2.7, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). Macrocystis surface canopies were noted to be low in many areas and Nereocystis was relatively abundant in some areas for this time of year. The survey boundaries were Point San Pedro in the north to Rincon Point in the south.

The total sea otter count, 2760, was 8.8% lower than the spring 2007 count (Table 1). However, it is important to note that the uncorrected counts are subject to a significant degree of year-to-year variance, associated with differences in counting conditions, otter distribution and other factors. Accordingly, the 3-year running average is the metric the U.S. Fish and Wildlife Service’s Southern Sea Otter Recovery Plan recommends using to reduce the influence of anomalously high or low counts from any particular year. The current 3-year running average for the population as a whole was almost unchanged from last year, at 2826 (Table 1). Although the overall trend suggests a slow-down in the rate of population recovery (Figure 1), there were substantial differences in dynamics observed across the sea otter’s range. Averaged over the last 5 years, the rate of change has been generally positive at the northern and southern peripheries of the range, but close to zero (or slightly negative) in the central portions of the range (Figure 2). The areas in the center of the range showing little or no growth also tend to be the regions with the highest density of sea otters (Figure 3).

Data on sea otter abundance, population dynamics and pup production are summarized for 14 segments of the California coastline in Table 2. Three of these coastal segments (all counted from the air) showed changes of at least 85 otters from the previous year’s survey. The count of independent otters in Monterey Bay was down by about 25% as compared to spring 2007 (Figure 4), although the viewing conditions this year were less favorable. There was also a substantial drop (>100 animals) in the Cayucos to Hazard Canyon segment (Estero Bay), and an increase of almost equal magnitude in the number counted between Pismo Beach and Point Sal. It is quite possible that some of these differences reflect movements of animals between areas, especially males and juveniles, as data from radio-tagged sea otters suggest that such movements are not uncommon.

The number of sea otters counted southeast of Point Conception, 71, was down slightly from the 2006 and 2007 spring surveys, although the number counted east of Gaviota (37) was similar to the number counted in 2007 (39). The majority of these animals were found in the area of Coal Oil Point, 8 km east of the group’s location last spring. Because of the continued presence of sea otters in this area, the mainland range of the southern sea otter is now considered to extend to Coal Oil Point, in Santa Barbara County, while the northern range boundary is considered to occur at the Tunitas Creek mouth in San Mateo County (Figure 5). The mainland range limits are defined as the points farthest from the range center (to the north and south) at which 5 or more otters are counted within a 10km contiguous stretch of coastline (as measured along the 10m bathymetric contour) during the two most recent spring censuses, or at which these same criteria were met in the previous year. It is not unusual to have a few animals counted outside of this official range: the southern-most sightings this year were two animals at Rincon Point, near the Santa Barbara/Ventura County line, while the northern-most sightings were two animals just north of Montara in San Mateo County (Figure 5). We occasionally receive reliable reports of sea otters – almost always single animals – beyond the boundaries of our survey. We believe the number of such animals is negligible, but we will continue to expand our survey search boundaries when more than one or two animals are reported to be in an area for extended periods.

The portion of the range within which reproduction occurs has remained relatively constant for the past 5 years, from Ano Nuevo in the north to Jalama Beach in the south. As with previous surveys, the highest ratios of pups to independent animals were seen within kelp-dominated areas in the central portion of the range (Figure 6). While the total pup count, 326, was the third highest on record, it was 63 less than the record high count last spring (Table 1). No pups were observed north of Pigeon Point or southeast of Point Conception during the survey, although the presence of one pup was verified in the latter area in early April of this year.

Further data summaries, in both tabular and GIS format, are available at the USGS-WERC web site: http://www.werc.usgs.gov/otters/ca-surveys.html. This survey is a cooperative effort between USGS-BRD-Western Ecological Research Center, CDFG–Marine Wildlife Veterinary Care and Research Center, Monterey Bay Aquarium, and many experienced and dedicated volunteers, including docents of the Point Lobos State Reserve and members of the Pacific Cetacean Group. Assistance was also received from staff of the U.S. Fish and Wildlife Service, the California Coastal Commission, and U.S. Minerals Management Service.