Identifying spatial relationships between marine biological hotspots and fronts in the Northern California Current using remote-sensing techniques

Biological hotspots in the marine environment are known to be important to virtually all fish functional groups as well as supporting higher biodiversity.  The goal of the present study is to identify the spatial relationship between marine fish ‘hotspots’ and surface water conditions in the northern California Current, using an innovative remote-sensing technique as opposed to our previous trawling method.  We used LIDAR (Light Detection and Ranging) from a small airplane to sample the surface waters over the continental shelf during August 2005.  Along the flight paths, we collected information on the spatial distribution of fish (surface nekton), sea surface temperature (SST), and chlorophyll concentration.  Satellite SST and chlorophyll data were also included to expand the LIDAR-sampled area.  Data were then incorporated into a GIS for spatial analyses.  Near-synoptic, daily SST and chlorophyll maps were created using a geostatistical approach to determine the locations of fronts.  The locations of nekton were then analyzed with respect to 1) proximity to SST and chlorophyll fronts, and 2) frontal density.  Results indicate that surface fish schools are often associated with fronts, suggesting that fronts may play an important role in the formation of biological hotspots.  Thus fronts, which can be determined via remote-sensing, could be used as indices of critical habitats.  This method will yield valuable information regarding the distribution of marine fish and habitat usage in a more cost-effective way than traditional sampling methods, and ultimately provide better information for management decisions and the design of marine protected areas.