Composite fish diversity off southern California

This map shows composite diversity averaged between 4 data sets: RecFIN recreational hook and line, SCCWRP trawls, NMFS benthic trawls, and kelp diver surveys. Diversity (H') was calculated independently for each of the four large datasets on a total of 364 species using the Shannon index of diversity (Shannon and Weaver, 1949). Using ArcGIS, 5 x 5 minute grids were created and mean diversity was calculated for each grid cell containing data. To provide an overall map of diversity, results from the four datasets were combined. To standardize, gridded results from each dataset were divided into quintiles with 5 denoting the greatest diversity and 1 the least diversity. The standardized diversity was averaged where more than one diversity estimate was available for a cell. Standardization re-scales the results from all datasets to the same scale. This process can remove some differences that result from variable collection methods; however, it can also minimize actual differences between habitats.