Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1500
Title: Where the wild things are: predicting hotspots of seabird aggregations in the California Current system
Author: Nadav Nur, Jaime Jahncke, Mark Herzog, Julie Howar, K. D. Hyrenbach, J. E. Zamon, D. G. Ainley, John A. Wiens, Ken Morgan, Lisa T. Ballance, Diana Stralberg
Publication Year: 2011
Journal: Ecological Applications
Volume: 21
Issue: 6
Pages: 2241-2257
Keywords: bagged decision trees, biodiveristy, habitat-association models, marine protected areas, marine rserves, pelagic ecosystems, remove-sensed data, seabirds, spatial predictive models

Marine Protected Areas (MPAs) are 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 Ecosystem, we identified areas predicted to support multi-species 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 US/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-leraning algorithm, bagged decision trees. Sincle-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 4 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 multi-species hotspots will depend on which group of species is of highest management priority. Modeling hotspots a a broad spatial scan can contribute to MPA site selection, particularly if complemented by fine-scale information for focal areas.

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