Fish diversity in southern California using trawl data from the National Marine Fisheries Service

The Shannon Index of diversity was calculated from National Marine Fisheries Service Groundfish Survey Program (NMFS GSP) fish trawl data. Data from 477 fishery independent trawls ranging from 55-1200 m in depth were collected June-November in 1977, 1989, 1992, 1995, and 1997-2002. Including all fish identified to the species level resulted in 189 fish species. Using ArcGIS, 5 x 5 minute grids were created and mean diversity was calculated for each grid cell containing data. Gear included a nor'eastern trawl (127 mm stretched-mesh body; 89 mm stretched-mesh codend; and 32 mm stretched-mesh codend liner) with a rubber bobbin roller which was trawled for 15-30 minutes on the bottom. Zimmerman's (2003) analysis of benthic species biomass was used to cull out the trawls that did not fish the bottom.