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Establishing a protocol for systematic surveys of stranded marine mammals in Humboldt County
Between October 2011 and September 2013, I designed and implemented an effort-based beach survey protocol for stranded marine mammals and seabirds in Humboldt County. This study was designed to create a baseline data set that is comparable to other programs in the state. I analyzed differences between historical records at Humboldt State University, findings from the systematic surveys, and findings from another program that conducts effort-based surveys for stranded marine vertebrates, the Coastal Observation and Seabird Survey Team (COASST). A mean of 6.0 x10-2 marine mammal carcasses per kilometer (encounter rate) was documented. Seasonal stranding patterns were detected for California sea lion and harbor seals. Three hotspots, or areas of higher encounter rates, were detected at the southern end of the survey range. The average number of marine mammal strandings per year and species diversity per year were compared to those of the historical stranding records from 1975 through 2010. There were more marine mammal strandings and more pinniped species per year documented during systematic surveys than in the historical records. On overlapping beaches, the encounter rate for seabird carcasses was lower for HSU’s MMSP than for COASST. HSU’s MMSP documented a higher encounter rate for marine mammal carcasses than COASST. This may be due to different methods, timing of surveys, or different objectives for the programs. In conclusion, protocol for systematic surveys was designed and pilot-tested, a baseline data set documenting stranding patterns in Humboldt County was established, and collaboration with another effort-based survey program was initiated.