Highly Migratory Species in the California Bight: Implications for Wildlife Disease
Abstract
The California Bight supports a diverse community of marine vertebrates, including four robust pinniped populations and at least a dozen resident or transient cetacean species. These species vary in their geographic and vertical use of the coastal marine environment. Marine mammals undergo seasonal migrations that carry them across U.S. political boundaries into Mexico or Canada and into habitats as diverse as the relatively remote offshore islands, to beaches and embayments near high-density urban areas, to regions impacted by agricultural or industrial runoff and sewage.1,2,3 They are therefore exposed to and regularly move among areas of varying water quality.4 “Pathogen pollution” from anthropogenic sources has been implicated as a contributory factor in wildlife diseases, including those affecting marine species.5,6 Epidemics of disease may result when infected animals move into an area occupied by naïve populations; conversely, healthy animals moving into new areas (e.g., in response to environmental perturbations such as El Nino7) may experience morbidity and mortality associated with endemic pathogens in that area.8 Infectious diseases in marine mammals vary in their etiology, pathogenesis, zoonotic potential and ecological impact. Pinnipeds may serve as reservoirs for pathogens that can have substantial impacts on terrestrial populations, including humans (e.g., influenza B virus9), domesticated food animals and terrestrial wildlife (e.g., brucellosis10). An understanding of marine mammal movements and disease exposure—not just in U.S. waters but in all the regions they inhabit—is critical to understanding marine ecosystem health in the California ecoregion.
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