Analyses/Maps

Fish

Petrale sole HSI map: Potential Distribution

About these maps:
These maps display HSI model results for subadult (left) and adult (right) petrale sole during June-November. The maps exhibit the potential distribution of the species based on affinities to bathymetry and substrate (see graphics below maps). 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; Wolotira et al., 1993; Vetter et al., 1995; Wilkins et al., 1998; PFMC, 1999; and Lauth, 2001.
Substrate SI: Pearcy, 1978; NOAA, 1990; Love et al., 1996; and CDFG, 2002.
Validation: Wilkins et al., 1998 and Turk et al., 2001.
Life stage information: PFMC, 2002.

Methods:
Bathymetry SI values for adults were developed using the literature review method, whereas subadult SI values were assigned based on the regression fitting technique using NMFS trawl data. For more detailed descriptions of these techniques, see the discussion of Habitat Suitability Modeling, Section 2.1.2, p. 34.

Results and Discussion:
Length at maturity information (PFMC, 1999) was used to differentiate adults from subadults. Adults were defined as: females > 432 mm and males > 381 mm total length. Depth preference for adults was determined using ranges reported from literature sources. Highest suitability was estimated to occur from 100 m to 449 m. Moderate suitability was observed from 50 to 99 m and from 450 m to 499 m. Depths greater than 650 were considered unsuitable. Subadult depth suitability was limited to shallower depths, ranging from 50 to 90 m. Moderate suitability was predicted over a greater range, 90 to 369 m. Depths greater than 510 m were unsuitable. Both adults and subadults exhibited preference for soft substrates exclusively. Rock/mud habitats were also ranked highly suitable. Based on these results, both adult and subadult potential high suitability occurred over much of the shelf area. These areas are more noticeable in the northern portion of the study area where the shelf is much broader. Large areas of potential high suitability for adults were predicted within Cordell Bank (814 km2), Gulf of the Farallones (1901 km2), and Monterey Bay (2915 km2) sanctuaries. Similar results were observed for subadults: Cordell Bank – 615 km2; Gulf of the Farallones – 1829 km2; and, Monterey Bay – 2603 km2. Significantly large areas (approximately 1000 km2) of high suitability were located outside sanctuary boundaries. These areas extend north from Cordell Bank and Gulf of the Farallones sanctuaries and south of Monterey Bay sanctuary. A smaller area of high and moderate suitability was located within rock/mud habitat approximately 59 km west of Point Sal.

NMFS trawl data were used to assess model performance. Although data were limited, strong positive correlations were observed between mean abundance and predicted HSI values. Additional fisheries independent data are required to strengthen the relationships for suitability indices and to provide additional data for model testing.