A Biogeographic Assessment off North/Central California

Analyses/Maps

Fish

HSI Integration - Shallow Shelf Assemblage
Shallow Shelf Assemblage Adult and Subadult

About these maps:
The maps displayed here provide one approach to assess habitat suitability based on HSI results for multiple species. HSI model results were averaged to assess the potential distribution of suitable habitats for 4 species of shallow water (70-150 m) shelf species. HSI values range in scale from 10 (highest) to 0 (unsuitable). HSI results were grouped into five classes: highest suitability (10-8), moderate (7-5), low (4-2), lowest (1), and unsuitable (0).

Data sources:
Adult and subadult HSI maps for English sole, lingcod, Pacific sanddab, and Petrale sole (CD-Rom).

Methods:
See HSI Methods (Section 2.1.2, p. 34) for HSI map development. Maps of mean HSI were developed by overlaying each individual HSI map and calculating the arithmetic mean across grid cells. Assemblages were determined by cluster analysis of NMFS triennial trawl survey data (see Section 2.1.1).

Results and Discussion:
English sole, lingcod, Pacific sanddab, and Petrale sole were representatives of a shallow water shelf assemblage. Potential high suitability was predicted to occur over shelf waters; however, adult suitability was predicted to occur at greater depths (50-125 m) than subadults (50-85 m). Approximately 13% of the study area was predicted to be potentially suitable for adults, whereas only 7% was predicted for subadults. While total area of high suitability was lower for subadults, total area of moderate suitability was greater. These areas extended from 85 m to 125 m. Depths greater than 500 m were considered unsuitable for both life stages. Relatively small bands of high suitability extend north and south of sanctuary boundaries.

Interestingly, the representative species that comprise this assemblage exhibit two differing substrate preferences. The soles prefer soft substrates, while lingcod prefer hard, rocky substrate. Mapped results exhibit low suitability for rocky substrates within the study area, while soft substrates are predicted highly suitable. Obviously, the results are biased based on the substrate affinity of the three flatfish species.