Analyses/Maps

Fish

Blue rockfish HSI map: Potential Distribution

About this map:
This map displays HSI model results for adult blue rockfish during June-November. The map exhibits the potential distribution of the species based on affinities to bathymetry and substrate. Predicted HSI values range in scale from 10 (highest) to 0 (unsuitable) and were grouped into five classes: highest suitability (10-8), moderate (7-5), low (4-2), lowest (1), and unsuitable (0). SI values for bathymetry and substrate type are shown in the graphics below the mapped HSI results. Model performance graphics and statistical details are displayed in the map insets.

Data Sources:
Bathymetry SI: Alverson et al., 1964; Miller and Geibel, 1973; Miller and Hardwick, 1973; Eschmeyer et al., 1983; Wilkins et al., 1998; and Love et al., 2002.
Substrate SI: Turner et al., 1969; Miller and Geibel, 1973; Feder et al., 1974; Love and Ebling, 1978; Hallacher and Roberts, 1985; and Love et al., 2002.
Validation: Wilson-Vandenburg et al., 1996.
Life stage information: Love et al., 2002.

Methods:
Bathymetry SI values for adult blue rockfish were developed using the literature review method. For more detailed descriptions of these techniques, see the discussion of Habitat Suitability Modeling.

Results and Discussion:
Lifestage information was reported by Love et al., 2002, and adults were defined as: females > 350 mm and males > 320 mm total length. Depth preference was calculated from reported ranges where nearshore waters to 100 m were considered the most suitable. Suitability was moderate from 100 to 200 m and low from 200 to 549 m. Depths greater than 549 m were considered unsuitable. Rocky substrate was the preferred substrate reported with no apparent distribution over soft substrates. Based on these data, model results depict limited areas of potential high suitable habitat. All rocky substrates on the shelf were predicted highly suitable, whereas all soft substrates were predicted unsuitable. Overall, less than one percent of the study area is potentially suitable for adult blue rockfish. Most of these areas are located in Monterey Bay sanctuary (149 km2) followed by smaller areas in the Gulf of the Farallones (91.4 km2) and Cordell Bank sanctuaries (38.3 km2). Potential suitability for habitats outside of sanctuary boundaries were predicted to be low or unsuitable.

Recreational catch data from CDF&G were used to assess model performance. Positive trends were observed between mean abundance and predicted HSI values; however, additional data are needed to support SI development and provide adequate data for testing model performance.