Where the wild things are: predicting hotspots of seabird aggregations in the California Current System

Abstract

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.

Using risk prediction models and species sensitivity maps for large-scale identification of infrastructure-related wildlife protection areas: The case of bird electrocution

“…For example, species distribution prediction models have been widely applied to optimize the design of protected aeas, e.g. marine reserves (Nur et al, 2011;Arcos et al, 2012;O'Brien et al, 2012), or to identify potential areas for protection in poorlyknown terrestrial ecosystems (e.g. Raxworthy et al, 2003;OrtegaHuerta and Peterson, 2004).…”

Persistence of hotspots and variability of seabird species richness and abundance in the southern California Current

“…First, from a food web perspective, biological hotspots in pelagic ecosystems are ecologically important areas with high concentrations of marine species where high rates of trophic transfer may occur (Nur et al 2011, Santora et al 2011b, Sigler et al 2012; thus, their identification will advance our understanding of how pelagic marine ecosystems are spatially organized. Moreover, little v www.esajournals.org is known about species richness patterns in marine ecosystems, so establishing where species richness hotspots form and are maintained is of great interest for advancing theory on how marine systems are structured (Myers et al 2000, Worm et al 2005.…”

“…Therefore, understanding trophic interactions within persistent seabird hotspots could benefit EBFM and development of harvest rules for forage fisheries. Third, marine spatial management in the CCE requires information on the distribution and connectivity of biological hotspots (Halpern et al 2009, Nur et al 2011, Santora et al 2011b, Adams et al 2012) in order to avoid potential negative interactions (e.g., seabirds and fishing vessels, oil spills; Hyrenbach et al 2000, Hooker and Gerber 2004, Lascelles et al 2012.…”

“…Quantifying biophysical drivers of seabirdforage hotspots will reduce uncertainty about numerical responses between seabirds and forage fish (Cury et al 2011, Santora et al 2014, and promote identification of critical marine habitat important for sustaining seabird populations in the CCE (Nur et al 2011, Adams et al 2012. To that end, numerical response models should compare the spatio-temporal persistence of seabird hotspots to long-term changes in hydrographic conditions and forage fish abundance.…”

“…The assessment of seabird populations at sea is dependent on the size of an area surveyed and the consistency and repeatability of surveys across many years (Nur et al 2011, Lascelles et al 2012, Santora and Veit 2013. Seabirds tend to concentrate in suitable foraging habitat; some species concentrate near the coast, whereas others are more oceanic and found 500þkm offshore (Hyrenbach and Veit 2003).…”