Analyses/Maps

Fish

Yelloweye rockfish HSI map: Potential Distribution

About this map:
This map displays HSI model results for adult yelloweye rockfish during June-November. The map exhibits the potential distribution of the species based on affinities to bathymetry and substrate (see graphics below map). 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; Allen and Smith, 1988; Wilkins et al., 1998; Yoklavich et al., 2000; and Love et al., 2002.
Substrate SI: Rosenthal, 1980; O’Connell and Carlile, 1993; Murie et al., 1994; Love et al., 1996; O’Connell et al., 1998; and CDFG, 2002.
Validation: Wilson-Vandenburg et al., 1996.
Life stage information: Love et al., 2002.

Methods:
Bathymetry SI values for adult yelloweye rockfish were developed using the literature review method. For more detailed descriptions of these techniques, see the discussion of Habitat Suitability Modeling, Section 2.1.2, p. 34.

Results and Discussion:
Adults were defined as females > 440 mm and males >400 mm total length (Love et al., 2002). Trawl information for yelloweye’s were not sufficient to develop SI values for depth, thus literature sources were used to establish relationships with depth and substrate. According to literature sources, adults prefer depths within 50-299 m and are absent at depths greater than 550 m. A strong preference was reported for hard substrate with rare occurrence over mud or sand. Mapped model results display very limited habitat that is highly suitable (less than 1% of the study area) and all are located within sanctuary boundaries. Most of these areas (228 km2) are intermittently located throughout Monterey Bay sanctuary at depths of approximately 150-275 m. Approximately 97 km2 (2.9%) of the Gulf of the Farallone’s available habitat was considered highly suitable, while 62 km2 (4.5%) of Cordell Bank’s available habitat was predicted highly suitable. Similarly, moderately suitable habitat was limited throughout the study area, comprising 1.3% of the total area. No moderately suitable areas were predicted within Cordell Bank or Gulf of the Farallones sanctuaries. The majority of this habitat occurred within a large area of mixed mud/rock in the southernmost region of the study area.

Model performance was assessed using CDFG recreational catch data. Although data were limited, positive correlations were observed between mean abundance and predicted HSI values. Additional data are required to strengthen suitability indices and validation assessment.