CA Harbor Seal Populations
Abstract: In May of 2001, the California Department of Fish and Game (CDFG) conducted an aerial photographic survey of the California coast and the offshore Channel Islands to obtain a minimum estimate of the population of harbor seals (Phoca vitulina richardsi) living in California. The developed photographs were examined to count the number of harbor seals present and determine the location of each haul-out site by comparison to photos taken in previous surveys. This survey was successful in obtaining nearly complete coverage of all known haul-out areas. The 1995 survey was the last complete coverage. The total county for 2001 is 12,312 harbor seals. This result is the lowest ever recorded by CDFG for a combined count of the mainland and all offshore islands. The California Department of Fish and Game (CDFG) conducted two surveys in 2002 in an attempt to provide better coverage and to lessen the chances of weather related problems. A total of 16 days were scheduled for aerial surveys from May 19 to July 19, 2002. Total count for Survey 1 was 10,541 harbor seals, while that for Survey 2 was 8,374 harbor seals. Camera problems that produced un-readable film and poor weather conditions prevented a complete assessment by either survey. The lack of complete coverage by either Survey 1 or 2 limited the total number of harbor seals counted. This is especially true in areas where past surveys revealed high concentrations of seals such as the northern Channel Islands and Point Reyes - Sonoma County coast. The California Department of Fish and Game (CDFG) conducted two aerial surveys in 2003 in an attempt to provide better coverage and to lessen the chances of weather related problems. A total of 20 days were scheduled for aerial surveys from May 25 to July 20, 2003. Complete coverage was achieved in both surveys. This was the first time CDFG conducted these surveys using a digital imaging camera. Total count for Survey 1 was 17,415, while that for Survey 2 was 17,778 harbor seals.
Purpose: The purpose of this project is to survey the abundance and distribution of harbor seals (Phoca vitulina richardsi) at all known haul-out sites in California coastal waters and offshore islands during the peak of the molt cycle.
Supplemental Information: CDFG has monitored the numbers of harbor seals on the mainland coast of California, as well as offshore islands during the peak of their molting season since the early 1980s. Funding from the Pacific States Marine Fisheries Commission allowed CDFG to continue that effort. CDFG has used a single survey to census harbor seals along the California coastline and offshore islands since 1982. Because of unexpected low counts for the 2001 survey, a workshop was convened to review methodologies and to make recommendations for future surveys. The West Coast Harbor Seal Abundance Workshop was held March 28-29, 2002 at the NOAA/NMFS Southwest Fisheries Science Center in La Jolla (Barlow 2002). The workshop participants concluded that the 2001 survey was most likely scheduled too early and missed the peak molt period. Recommendations for the 2002 survey included: 1) splitting the survey into a southern California section (Channel Islands and the southern central coast to Point Sur) and a northern California section (the northern central coast and remainder of California north coast), 2) conducting the southern section in May or June and the northern section in July to more closely follow the peak molt period. 3) surveying the Channel Islands in the afternoon may be more important tha The protocol used for this survey was essentially the same as that originally developed by Miller et al (1983), and last reported in Fluharty (1999). We have added our own improvements by taking advantage of new technology. The mainland coast as well as the Channel Islands were surveyed using the Department's twin engine, high wing Partenavia P68 "Observer ll" aircraft. This aircraft is equipped with a large photographic-observation port located in the floor of the aircraft behind the pilot's and copilot's seats. Use of this port enabled the photographer to locate and identify harbor seals and photograph them from directly overhead. The survey was conducted from an altitude of 600 to 700 feet, with an average altitude of 650 feet, depending on visibility and other conditions. In 2001 Color photographs were taken using a motor-driven Hasselblad 2003 FCW camera, Zeiss F3.5 100mm lens and large capacity film magazines containing 70mm Kodak E100S Ektachrome Professional film. In 2003 For 2001, the aerial photographic surveys were scheduled and flown on May 1, 2, and 3 for the Channel Islands, and on May 14-17 for the mainland. The mainland survey started at Point Mugu and finished at the Oregon border. All areas of San Francisco Bay and all major rivers and bay were covered. Approximately 30 miles of coastline north of Santa Cruz and just south of Half Moon Bay were not covered due to low lying coastal fog. We tried to re-survey that area later in the day, but the fog was still present. The mainland survey was completed in four days without further incident. Weather, visibility and tidal conditions were optimal over most of the survey period. Ground counts were obtained for Children's Pool and Seal Rock in La Jolla, San Diego County just prior to the mainland aerial survey. We requested and obtained ground counts for the Farallon Islands for the time period of the mainland survey. For 2002 the survey was conducted form May 19 through July 19. For 2003 the survey was conducted
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