Species Richness (Number of Species per Haul)
A total of 142 species of fish were taken during the survey (Table IV-5). The number of fish species per haul ranged from 3 to 25. The lowest value occurred in the southern region within bays and harbors and the highest number of species occurred in the southeast Channel Islands within the middle shelf zone. The median for the SCB as a whole was 12 species per haul, with subpopulation medians ranging from 8 (inner shelf small POTWs) to 18 (upper slope Channel Islands). More of the area with species richness above the Bight median occurred in the island region than in the mainland region (Table IV-5; Appendix B-B7). Among the islands, the southeast and northwest Channel Islands were identical (both with a median of 16 species). Among the mainland region subpopulations, only the southern region had a median (14) above that of the Bight median, while the northern region (9) was lower and central region (12) the same. Of the five major shelf zones, the middle shelf had the highest median number of species, followed by the outer shelf, upper slope, inner shelf, and bays and harbors; with medians of 16, 15, 9, 9, and 8, respectively. Within the upper slope zone (Table IV-5; Appendix B-B8), the island region had greater species richness than the mainland region. Within all shelf zones, the large POTWs had the highest median number of species.
Comparing the regions within the shelf zones (Table IV-6; Appendix B-B9) revealed that the median number of species (18) occurred at the northwest Channel Islands on both the outer shelf and upper slope. Trawl stations were divided into four richness groups (Figure IV-2). Stations within the highest richness group (20 to 26 species per haul) were primarily located in the middle and outer shelf (Figure IV-2; Tables IV-5 and IV-6).
Table IV-3. Demersal fish biomass by subpopulation at depths of 2-476 m on the shelf and upper slope of southern California, July-October 2003.
Table IV-4. Demersal fish biomass by region within shelf zone subpopulations at depths of 2-476 m on the shelf and upper slope of southern California, July-October, 2003.
Table IV-5. Demersal fish species by subpopulation at depths of 2-476 m on the shelf and upper slope of southern California, July-October 2003.
Table IV-6. Demersal fish species by region within shelf zone subpopulations at depths of 2-476 m on the shelf and upper slope of southern California, July-October, 2003.
Figure IV-2. Distribution of fish biomass per haul at depths of 2-476 m on the southern California shelf, July-October 2003.
Figure IV-3. Distribution of number of fish species per haul at depths of 2-476 m on the southern California shelf and upper slope, July-October 2003.
Share with your friends: |
