Relating Population Abundance of Groundfish Species to Habitats Using Predictive Models and Broad-scale Seafloor Maps

Principal Investigator: Mary Yoklavich
Co-Principal Investigator: Lisa Wedding

Mary YoklavichDeep rocky banks and outcrops, underwater pinnacles, and submarine canyons are important habitats for hundreds of species of demersal fishes in California waters. Rocky areas on the continental shelf and upper slope off central California are dominated by more than 40 species of rockfishes, of which seven have been declared overfished by NOAA Fisheries. Sedentary rockfishes living in heterogeneous high-relief rocky habitats are particularly difficult to appraise accurately with conventional methods such as bottom-trawl gear. The first objective of this project is to develop statistical models that predict densities of individual demersal fish species and multispecies fish assemblages over broad spatial scales. We will base these models on a number of associated habitat variables (e.g. depth, substratum type, patch size and configuration) and the densities of co-occurring fish species, using a subset of our database from central California. Issues related to spatial scale also will be explored. The second objective is to couple these models with the broad-scale seafloor habitat maps in a geographical information systems (GIS) environment to forecast fish densities on a regional basis. Such efforts have been limited in deep water systems because of the lack of detailed habitat maps from which broad-scale fish densities can be derived. RockfishThe recent availability of detailed and accurate habitat maps from the multibeam-acoustic surveys of the seafloor within California’s territorial waters makes this proposed effort possible. From these predictive models and maps of density for various demersal species, population size (total abundance and biomass, when coupled with size composition) can be estimated in the study area. , in addressing such needs as (1) the design and monitoring of marine protected areas, (2) identification of essential fish habitats, and (3) identification of areas important to the restoration or rebuilding of depleted stocks.

The spatial models of rockfishes and habitats developed during this project are the focus of a new project that is focused on extending the geographic and temporal scope of these efforts in support of stock and habitat assessments relevant to NOAAs Habitat Blueprint Southwest Regional Initiative in the Southern California Bight (SCB).