California Sea Lion Stranding Records from Quantifying the linkages between California sea lion (Zalophus californianus) strandings and particulate domoic acid concentrations at piers across Southern California

Pacific Marine Mammal Center (PMMC) is a member of the West Coast Marine Mammal Stranding Network, which was established under the United States Marine Mammal Protection Act by the National Oceanic and Atmospheric Administration (NOAA) to respond to stranded marine mammals. PMMC rescues, rehabilitates, and releases sick and injured marine mammals along the Orange County coastline, which is approximately 68 km of the Southern California coastline (Figure 1). All marine mammal rescue and rehabilitation activities are conducted by PMMC under a Stranding Agreement with National Marine Fisheries Service/NOAA.

Patient case records from 2015-2019 for California sea lions (hereafter, sea lions) were reviewed and collated for each animal’s case presentation including sex, age class, seizure activity, postictal signs, comatose, abortion, and whether the sea lion was diagnosed by the attending veterinarian with domoic acid intoxication following the behavioral diagnostic criteria outlined by Gulland et al., (2002). Multiple veterinarians made diagnoses during the time series based on these criteria which may have introduced some variation in the diagnosis of domoic acid intoxication during the study period. Age classes were defined following Greig et al. (2005) using dentition, straight length, pregnancy status, and sexual dimorphism to classify a sea lion’s age class. The following demographic categories are included in this study: juvenile/subadult male, subadult female, adult male, and adult female. Younger sea lions in the pup and yearling age classes were excluded as sea lions within these age classes are generally the most common patients at the center and often strand due to malnutrition (Bejarano et al., 2008a), and rarely present with acute or chronic domoic acid intoxication during blooms. Adult and subadult age classes are the most commonly affected by domoic acid intoxication (Bejarano et al., 2008a). Only live sea lions that were rescued on the Orange County coastline, brought to PMMC's facility, and assessed by the attending veterinarian were included. Adult and subadult sea lions that died on the beach were excluded from the study cohort because an attending veterinarian could not assess clinical signs to diagnosis domoic acid intoxication prior to death.