Analyses/Maps
Fish
Bocaccio HSI map: Potential Distribution
About these maps:
Figure 34 displays HSI model results for subadult (left) and adult (right) bocaccio during June-November. The maps exhibit 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; Feder et al., 1974; Dark et al., 1983; Gunderson and Sample, 1980; Tagart and Kimura, 1982; Eschmeyer et al., 1983; Allen and Smith, 1988; Love et al., 1990; Wolotira et al., 1993; Wilkins et al., 1998; Yoklavich et al., 2000; Lauth, 2001; and Love et al., 2002.
Substrate SI: Feder et al., 1974; Eldridge, 1994; Yoklavich et al., 2000; and Love et al., 2002.
Validation: Wilson-Vandenberg et al., 1996; Wilkins et al., 1998; and Turk et al., 2001.
Life stage information: Love et al., 2002.
Methods:
Bathymetry SI values for adult bocaccio were developed using the literature review method, whereas subadult SI values were assigned based on the regression fitting technique using NMFS trawl data.
Results and Discussion:
Length at maturity information (Love et al., 2002) was used to determine life stage for bocaccio. Adults were defined as: females >360 mm and males >350 mm total length. Depth suitability for subadults was highest from 90-270 m while highest suitability for adults was similar, ranging from 50-299 m (Figure X). Literature sources indicate that adult bocaccio are almost exclusively found around rocky substrates, while subadults exhibit broader affinity among substrate types (Figure X). Comparison of the two HSM maps show that the marked difference in substrate preference for adults yields a more limited spatial distribution than subadults. Less than 5% of the available habitat within each sanctuary was predicted highly suitable (HSI values >8) for adult bocaccio (Cordell Bank – 4.6%, Gulf of Farallones – 2.9%, Monterey – 1.7%) Within the study area, habitat of high suitability occurs exclusively inside sanctuary boundaries. High suitability covers more area for subadults than adults and extends well beyond sanctuary boundaries. Nearly 10% of Cordell Bank’s sanctuary was considered highly suitable for subadults. This percentage drops to 1.6% for Gulf of Farallones, and 2.6% for Monterey. Approximately 556 km2 of potential high suitable habitat was located within the three sanctuaries, while an additional 355 km2 were predicted outside sanctuary boundaries. Although the proportion of highly suitable habitats were similar for adults and subadults, large areas of potentially moderate suitability for subadults were observed throughout the study area; whereas no areas were predicted moderate for adults.
Generally, subadult bocaccio are more commonly found in shallower waters than adults (Love et al., 2002). Current scientific literature does not provide enough information to develop depth SI values for subadults; therefore, limited trawl information was used to develop SI values for bathymetry. Despite this, model performance for subadults yielded a strong positive correlation between observed abundance estimates from CDFG recreational catch data and predicted suitability (see map inset). Model performance for adult bocaccio also exhibited a strong positive correlation between predicted suitability and CDFG catch data. More information regarding bocaccio life history requirements are necessary to strengthen the HSI models; however, the mapped results and validation based on currently available information provide an adequate delineation of potential habitat suitability for adult and subadult bocaccio.