Steller sea lion (Eumetopias jubatus) strandings and the role of pathogens in reproductive failure

Abstract

Steller sea lions (SSL, Eumetopias jubatus) have faced severe population fluctuations over the last five decades with a myriad of possibilities affecting their SSL population including disease, malnutrition, predation, climate change, entanglement in marine debris, and other factors. This thesis examined the effects that anthropogenic factors and disease may play in SSL strandings and reproductive failure. The goal of this study was to characterize long-term seasonality and spatial trends in SSL strandings and to investigate the role Brucella spp., Coxiella burnetti. Chlamydophila spp. and morbilliviruses may play in reproductive failure including spontaneous abortion and premature parturition. In Chapter 1, we utilized stranding data (n=1507) collected in Alaska, Oregon, and Washington from 1990-2015. We assessed temporal trends by identifying seasonality patterns across all years, analyzing sex, age class, body length, and characterizing signs of human interaction including factors contributing to mortality. Clear seasonality trends were evident, with the greatest number of reported strandings occurring during the spring and summer. Gunshot wounds and fishery interactions accounted for a large proportion (46%) of human interaction cases in strandings. Adult males were the most frequently stranded sex and age class in the Alaska and West Coast Regions. This study attempted to quantify efforts to monitor strandings and determined that the apparent increase in strandings following 2000 was likely due to increased stranding response effort resulting from increased federal grant awards. We encourage conducting further spatial analyses of strandings in addition to continued stranding surveillance monitoring with attempts to improve stranding response time. In Chapter 2 of my thesis, we analyzed archived lung, skin lesion and placenta tissues for the pathogens of interest in SSL fetuses (n=18) and neonatal pups (n=2) collected from 1998 2015 in Alaska. Associated pathological findings and morphometric data were examined to identify signs of pathology or abnormalities in all cases. Marine mammal Brucella was detected in the lung tissue of three cases. This is the first documented detection of Brucella in SSL by PCR methods. Phocine distemper virus was also detected in the skin lesion of two cases and in the placenta of one case, in which the cases with skin lesions exhibited abnormal pathology that included vesiculoulcerative dermatitis. Currently, there is very little available information on the significance of Brucella spp. and morbilliviruses in marine mammal populations inhabiting Alaskan waters. Therefore, this study demonstrates the clear need to continue disease surveillance programs and further investigate the role disease may play in SSL reproductive health, and more generally on cohort population stability.