Analyses/Maps
Fish
Recreational Hook and Line Data from the California Department of Fish and Game (CDF&G)
Managers
have recently begun to understand the importance of studying entire
ecosystems rather than looking at each species individually. This
study took a first step in clarifying multi-species interactions
by determining which species tended to be caught together, and where.
Multivariate statistics were used to analyze fish species assemblages
on the scale of the recreational fishery over marine habitats off
central California. This data set, while fishery dependent, includes
demersal, as well as midwater species captured on variable habitats
including rock, mud, and sand. Some species and habitats in this
analysis are not covered with the other data sets in this study,
and therefore provide complimentary information. Twenty-seven fish
species were grouped into seven species assemblages (Figure), and
4,357 trip/location combinations were grouped into eight site groups
(Table). Unfortunately, due to the nature of the data set, exact
fishing locations could not be mapped. Therefore, the mean depth
associated with each site group is provided in conjunction with
a map showing the fishing locations in 2.5 minute grids, which were
color coded according to the average depth of the fishing trips
within the grid cell. The two analyses mentioned above provide information
on species which were caught together, and locations with similar
catch, but how can these two results be combined? The average frequency
of occurrence of species assemblages (percent occurrence calculated
for each species and then averaged for each fish assemblage) within
each site group was calculated to analyze the interaction between
the species assemblages and site groups (Table). As with all data
sets in this assessment, the most significant result was the effect
of depth. This supports previous work done by Williams and Ralston
(2002), Sullivan (1995), Field et al. (2002), Gabriel and Tyler
(1980), and Matthews and Richards (1991), who found bathymetry to
be an important factor in defining fish assemblages. All attempts
to isolate and remove the effects of depth in order to determine
secondary effects were unsuccessful. Certainly, secondary effects
exist, but at the scale of this study they were not discernible.
Through this analysis, a large amount of information has been condensed
to assemblages of co-occurring species, as well as groups of similar
locations. A map is provided to visually portray the spatial arrangement
of the results.
| Group 26 meters | Group 40 meters | Group 44 meters | Group 59 meters | Group 64 meters | Group 77 meters | Group 98 meters | Group 125 meters | |
|---|---|---|---|---|---|---|---|---|
| N | 581 | 688 | 183 | 235 | 1,501 | 207 | 683 | 279 |
| Depth±SD(m) | 26±13a | 40±16b | 44±27b | 59±26c | 64±18d | 77±22e | 98±21f | 125±32g |
| Gopher Assemblage | 0.36 | 0.23 | 0.14 | 0.09 | 0.09 | 0.01 | 0.01 | 0.00 |
| Blue Assemblage | 0.72 | 0.74 | 0.07 | 0.19 | 0.69 | 0.20 | 0.07 | 0.00 |
| Yellowtail Assemblage | 0.22 | 0.42 | 0.08 | 0.31 | 0.74 | 0.31 | 0.57 | 0.08 |
| Bocaccio Assemblage | 0.01 | 0.05 | 0.00 | 0.05 | 0.23 | 0.25 | 0.43 | 0.22 |
| Greenspotted Assemblage | 0.00 | 0.00 | 0.02 | 0.02 | 0.07 | 0.10 | 0.50 | 0.59 |
| Pacific Mackerel Assemblage | 0.02 | 0.07 | 0.13 | 0.07 | 0.12 | 0.17 | 0.09 | 0.06 |
| Quillback | 0.01 | 0.06 | 0.05 | 0.04 | 0.09 | 0.01 | 0.02 | 0.00 |