Fish diversity ranged from 0.18 to 2.29 bits/individual/haul (Table IV-7). The lowest value (0.18) occurred in the other (non-POTW) mainland subpopulation of the southern inner shelf. The highest value (2.29) occurred in the mainland region in the southern upper slope zone. The median for the Bight as a whole was 1.62, with subpopulation medians ranging from 0.66 (inner shelf, large POTWs) to 2.08 (islands, upper slope). Diversity was slightly higher (more area above the Bight median) in the mainland region than in the island region (Table IV-7; Appendix B-B10). Among the mainland region subpopulations, only the southern region had a median (1.77) above that of the Bight median, while the central (1.43) and southern regions (1.62) were slightly less. Among the islands, the northwest Channel Islands had greater diversity of fish (1.69) than the southeast Channel Islands (1.50; Table IV-7). Comparing among shelf zones, the middle shelf had the greatest median diversity, followed by the outer shelf, upper slope, inner shelf, and bays and harbors; with medians of 1.70, 1.68, 1.61, 0.99, and 0.91, respectively.
Within the upper slope subpopulation (Table IV-7; Appendix B-B11), the islands had higher diversity than the mainland. In the outer shelf zone, large POTWs had the highest diversity. Within both the middle and inner shelf zones, small POTWs had the highest diversity.
The regions within the shelf zones were also compared (Table IV-8; Appendix B-B12). This comparison revealed the greatest median diversity (2.08) was in the northwest Channel Islands within the upper slope zone. Trawl stations were divided into four diversity groups (Figure IV-4). Stations within the highest diversity group (2.04 to 2.29 per haul) were primarily located in the middle and outer shelf (Figure IV-4; Tables IV-7 and IV-8).
Table IV-7. Demersal fish diversity by subpopulation at depths of 2-476 m on the shelf and upper slope of southern California, July-September 2003.
Table IV-8. Demersal fish diversity 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-4. Distribution of fish diversity (Shannon-Wiener) per haul at depths of 2-476 m on the southern California shelf, July-October 2003.
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