Entangled seabird and marine mammal reports from citizen science surveys from coastal California (1997–2017)

Marine fauna in the California Current System is susceptible to entanglement in anthropogenic debris. We examined beach survey data from six California counties to describe trends of entangled marine birds and mammals (1997–2017). Surveyors reported 357 cases of entanglements among 65,604 carcasses. Monterey County had the greatest average entanglement rate (0.007) of surveyed counties, however, was not statistically different from Santa Cruz (p > 0.05). Twenty-six seabird species (97%) and three marine mammal species (3%), and three non-marine birds were affected. Numerically, Common Murre (23%), Brandt's Cormorant (13%), Western Gull (9.6%), Sooty Shearwater (8%) and Brown Pelican (7%) were the most affected due to abundance, but their entanglement rates were not statistically different (p > 0.05). The most vulnerable species were those frequently documented as entanglement despite low deposition numbers (Merganser spp. 25%). Entangling material consisted primarily of monofilament line (some hooks/lures), but other entanglement items were reported. •We report 354 entanglements between 1997 and 2017.•Seabirds accounted for 97% of all entanglements.•Five seabird species comprised 61.3% of total entanglements.•Seabirds were entangled primarily in monofilament fishing line.•Average annual entanglement rates between counites were not statistically different.