Analyses/Maps
Fish
California market squid HSI map: Potential Distribution
About this map:
This map displays HSI model results for adult California market
squid 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), high (7-5), moderate (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: Wilkins et al., 1998 and Lauth, 2001.
Substrate SI: Street, 1983; Maupin, 1988; CALCOFI, 1999; Leet et
al., 2001; and CDFG, 2002.
Validation: Wilkins et al., 1998 and Turk et al., 2001.
Methods:
Bathymetry SI values for adult California market squid were developed
using 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 x.
Results and Discussion:
Length data for market squid captured in NMFS trawls were not available,
thus the data most likely represent adult and juvenile individuals.
Determining depth affinities by life stage from the literature was
difficult, thus the two life stages are grouped together for these
analyses until additional information becomes available. As such,
squid depth preference was predicted to occur in nearshore waters,
up to depths of 90 m. Depths greater than 190 m were considered
unsuitable. No data were available for depths within 1-50 m, which
is probably preferable squid habitat based on the frequency of abundance
of squid landings in the 50-90 m range. Market squid are primarily
pelagic; however, literature sources revealed affinity for soft
substrate due to spawning activities; therefore mud and sand substrates
received higher SI values than hard substrates. Mapped model results
based on these SI values display the majority of highly suitable
habitat in the northern region of the study area where the shelf
is broader. Highly suitable habitat does exist in the southern portion;
however, it is narrow in width south of Monterey Canyon. Overall,
6.4% of the study area was considered highly suitable for market
squid. Within the Gulf of the Farallones sanctuary, high suitability
covers almost 38% of the available habitat, while only comprising
8.7 and 10.4% of available habitat in Cordell Bank and Monterey
sanctuaries, respectively.
Model performance was assessed by regressing predicted HSI values on mean abundance values from NMFS trawl samples (1998-2001). A strong positive correlation existed between predicted HSI value and mean abundance (see map inset). More information is recommended to refine SI values for both depth (i.e. 0-50 m depths) and substrate. Additional life history information is also needed to examine habitat shifts in relation to squid growth.