Using seabird habitat modeling to inform ocean zoning in Central California's National Marine Sanctuaries
Understanding seabird habitat preferences is critical to future wildlife conservation and threat mitigation in California. The objective of this study was to investigate drivers of seabird habitat selection within the Gulf of the Farallones and Cordell Bank National Marine Sanctuaries to identify areas for targeted conservation planning. We used seabird abundance data collected by the Applied California Current Ecosystem Studies Program from 2004-2011. We used zero-inflated negative binomial regression to model species abundance as a function of near surface ocean water properties, distances to geographic features and oceanographic climate indices to identify patterns in foraging habitat selection. We evaluated seasonal, inter-annual and species-specific variability of at-sea distributions for the five most abundant seabirds nesting on the Farallon Islands: western gulls (Larus occidentalis), common murres (Uria aalge), Cassin’s auklets (Ptychorampus aleuticus), rhinoceros auklets (Cerorhinca monocerata) and Brandt’s cormorants (Phalacrocorax penicillatus). The waters in the vicinity of Cordell Bank and east of the Farallon Islands emerged as highly selected foraging areas across all species. Further, we conducted a preliminary Marxan exercise to optimize seabird conservation areas where potential human-wildlife conflicts would be minimized. We explored three conservation targets where 10, 30 and 50 percent of these highly selected foraging areas would be conserved. We compared results in relation to existing marine protected areas (MPAs) and the future alternative energy footprint identified by the California Ocean Uses Atlas. Our results show that the majority of primary seabird habitat selected by Marxan lies outside of state MPA’s where threats from shipping, oil spills, and offshore energy development remain. This analysis illustrates a method for innovative marine spatial planning efforts and provides a foundation upon which to build more comprehensive zoning and management in California’s National Marine Sanctuaries.