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Marine protected areas (MPAs) provide an important tool for conservation of marine ecosystems. To be most effective, these areas should be strategically located in a manner that supports ecosystem function. To inform marine spatial planning and support strategic establishment of MPAs within the California Current System, we identified areas predicted to support multispecies aggregations of seabirds ("hotspots"). We developed habitat-association models for 16 species using information from at-sea observations collected over an 11-year period (1997-2008), bathymetric data, and remotely sensed oceanographic data for an area from north of Vancouver Island, Canada, to the USA/Mexico border and seaward 600 km from the coast. This approach enabled us to predict distribution and abundance of seabirds even in areas of few or no surveys. We developed single-species predictive models using a machine-learning algorithm: bagged decision trees. Single-species predictions were then combined to identify potential hotspots of seabird aggregation, using three criteria: (1) overall abundance among species, (2) importance of specific areas ("core areas") to individual species, and (3) predicted persistence of hotspots across years. Model predictions were applied to the entire California Current for four seasons (represented by February, May, July, and October) in each of 11 years. Overall, bathymetric variables were often important predictive variables, whereas oceanographic variables derived from remotely sensed data were generally less important. Predicted hotspots often aligned with currently protected areas (e.g., National Marine Sanctuaries), but we also identified potential hotspots in Northern California/Southern Oregon (from Cape Mendocino to Heceta Bank), Southern California (adjacent to the Channel Islands), and adjacent to Vancouver Island, British Columbia, that are not currently included in protected areas. Prioritization and identification of multispecies hotspots will depend on which group of species is of highest management priority. Modeling hotspots at a broad spatial scale can contribute to MPA site selection, particularly if complemented by fine-scale information for focal areas.

Tidal rips and jets are common features associated with archipelagos and complex coastlines. In habitats where rips and jets develop, energy flow to piscivorous predators is hypothesized to be strongly associated with tidal phase due to interactions between currents, plankton, and schooling planktivorous fishes (the 'tidal coupling hypothesis'). This study tests 1 component of the tidal coupling hypothesis, that the feeding activity of piscivorous predators and the availability of planktivorous fishes are both strongly associated with the same tidal phase. During 1994 to 1997, I made visual counts of actively feeding, mixed-species seabird flocks and hydroacoustic measurements of the relative abundance and distribution of schooling fishes. Median feeding activity, median backscatter m -1 transect, and median prey encounter probabilities were greatest during the tidal periods Slow flood 1 and Fast flood. Positive feeding anomalies and positive prey-encounter anomalies were significantly associated with tidal flood phases, but positive backscatter anomalies were not. The results support the tidal-coupling hypothesis, but suggest that changes in the distribution or behavior of schooling fish are as important as, if not more important than, changes in relative fish abundance when determining prey availability and predator foraging-success. The data show that tidal currents can play an important role in structuring nearshore predator-prey interactions.

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