Center for Coastal Monitoring and Assessment (CCMA)

Analyses/Maps

Biogeography of Fishes

The biogeography of fishes section is a robust statistical analysis of fish and a few economically important macro-invertebrates. A two-pronged approach was conducted to examine both fisheriesdependent and independent catch data and model the potential distribution and relative abundance of selected species (Figure 8). Analysis of fisheries data can be a slow process which often requires extensive exploratory statistical techniques to increase our understanding of the data before presenting reliable and salient results. Many data sets were evaluated, however, only four data sets that were spatially comprehensive within the study area were analyzed: 1) the California Department of Fish and Game fishery dependent recreational fishing trips targeting rockfish (CDF&G recreational); 2) the National Marine Fisheries Service fishery independent benthic trawls on the continental shelf (NMFS shelf trawls); 3) NMFS fishery independent benthic trawls on the slope (NMFS slope trawls); and 4) the NMFS fishery independent trawls in midwater (NMFS midwater trawls). Detailed information on these trawls is given in each respective section. The NMFS trawls on the continental shelf and slope provide information on the diverse demersal fish assemblages found on trawlable habitats between 50 and 1280 meters depth throughout the study area. Pelagic fish encountered either as the trawl descended or ascended are also included with these analyses. The CDF&G recreational hook and line data complements the NMFS data sets by providing information on midwater as well as demersal species. The recreational data was collected over soft bottom and hard bottom habitats between 5 and 200 meters depth. The NMFS midwater trawl data targets juvenile rockfish and provides information on fish and invertebrates found in the neritic environment during the upwelling season. Even though the spatial extent of this data set does not cover the entire study area, it provides a source of information on the neritic environment, which is important as juvenile habitat, and as the base of the food web for marine birds, fish, and marine mammals.

Due to time constraints, analysis of all species individually was not feasible. Instead, all four data sets were analyzed using multivariate statistics to identify species assemblages, site groups, and the location of the species assemblages in space using a Geographic Information System (GIS). For the multivariate statistics, species were included in an analysis if they were captured in at least 5% of the collections. Through all four data sets, 119 species were analyzed. A complete list of species included in the assemblage analyses can be found on the CD-ROM. In addition, community metrics, including species richness, species diversity, and rockfish richness were calculated for the NMFS shelf and slope trawls and the results presented spatially using GIS. However, due to spatial and temperal limitations of available data, (i.e. NMFS demersal trawls have no information on rocky or shallow areas (<50 meter) and contain trawls only for the months of June through November) areas such as Cordell Bank and the Farallon Islands are not adequately sampled. Therefore, habitat suitability modeling (HSM) was conducted to supplement the analysis of catch data, and to model the potential distribution of fish and invertebrate species across the study area (Brown et al., 2000). Thirty two species of fish and invertebrates were initially investigated through literature searches to determine if sufficient information was available to model potential distributions. The process of determining which species to include in the modeling procedure included consultation by the sanctuary staff, and integration of information on the economic and ecological importance of the species as well as initial results on species assemblages. Of the 32 species initially investigated, there was sufficient information available to conduct HSM on the adult and subadult stages of 14 fish species, and adult stage of 4 fish and 2 invertebrate species. Habitat suitability models were either derived from an analysis of a portion of the NMFS trawls on the continental shelf and slope or derived from species habitat affinities described in the literature. Model results were validated with NMFS trawls on the shelf and slope (a different subset than that used to create the affinities) or CDF&G recreational catch data. Model results for 3 species are included in the main body of this document, with the models for the rest of the species included in the CD-ROM.