Biointegrity indices for fish, invertebrates, and combined fishes and invertebrates (Allen et al. 2001a) were used to assess the extent of altered assemblages on the southern California shelf. Two fish indices, the fish response index (FRI) and fish foraging guild (FFG) index were used to assess alterations in fish assemblages. The FRI was applied to the entire survey area whereas the FFG was applied only to the middle shelf area. The megabenthic invertebrate response index (MIRI) was used for invertebrate effects and the trawl response index (TRI) was used for combined fish and invertebrate effects. Index values by station are given in Appendix D-D14.
Based on the FRI, 96% of the area of the SCB (165 stations) was classified as reference (normal) and 4% (25 stations) as nonreference (abnormal or disturbed); no index could be calculated for 1 station in San Diego Bay and 24 on the upper slope due to being shallower or deeper, respectively, than the range of 10-200 m depth range from which the index was developed (Figures VI-17 through VI-19). The highest percent of nonreference area in a subpopulation for fish assemblages was on the inner shelf (24%), followed by bays and harbors (15%); none of the middle shelf sites were classified as nonreference and only a few outer shelf stations were nonreference (Figures VI-17 and VI-18). Inner shelf small POTWs had the highest percent of nonreference area in the inner shelf zone (47%), followed by other mainland inner shelf areas (24%; Figure VI-18). Some of the nonreference inner-shelf POTW areas had high abundance of speckled sanddab and curlfin sole; the latter species was typical of the Palos Verdes Shelf in 1970s but not so in the 1980s and 1990s.
The FFG index indicated that 81% of the middle shelf zone was classified as reference and 19% classified as nonreference for fish assemblages (Figure VI-20). In the middle shelf zone where the index was applied, the Channel Islands had the highest percent of nonreference area for a region (41%). Of two subpopulations in this region (NW Channel Islands and Southwest Channel Islands), 46% of the NW Channel Islands and 36% of the SW Channel Islands were nonreference (Figures VI-20 and VI-21).
Figure VI-17. Percent of nonreference area by subpopulation on the southern California shelf and upper slope at depths of 2-476 m for the Fish Response Index (FRI), July-October 2003.
Figure VI-18. Percent of nonreference area by shelf zone subpopulation on the southern California shelf and upper slope at depths of 2-476 m for the Fish Response Index (FRI), July-October 2003.
Figure VI-19. Distribution of response levels for Fish Response Index (FRI) on the southern California shelf at depths of 2-476 m, July-October 2003.
Figure VI-20. Percent of nonreference area by shelf zone subpopulation on the southern California shelf and upper slope at depths of 2-476 m for the Fish Foraging Guild Index (FFG), July-October 2003.
Figure VI-21. Distribution of response levels for Fish Foraging Guild Index (FFG) on the southern California shelf at depths of 2-476 m, July-October 2003.
For the MIRI index, 84% of the area of the SCB was classified as reference and 16% as nonreference; an index could not be calculated for 30 stations in the area, mostly on the upper slope and in San Diego Bay. By shelf zone, the highest percent of nonreference area for invertebrate assemblages was in bays and harbors (53%), followed by the inner shelf zone (32%) (Figure VI-22). By human-influence subpopulation, all bay/harbor subpopulations were relatively high in nonreference areas, with the other mainland subpopulation being the highest (64%; Figure VI-23). Similarly, all mainland region inner shelf populations were relatively high in nonreference areas, with the other mainland subpopulation (usually near river mouths) being the highest (64%). In the bay/harbor subpopulation, nonreference sites were most common in LA/LB Harbor (Figure VI-24). The index could not be calculated for a relatively high number of sites in San Diego Bay and the upper slope due to insufficient numbers of appropriate species for calculating the index.
Using the TRI, 92% of the area of the SCB was classified as reference and 8% as nonreference. The TRI had the highest percent of nonreference area in the bays and harbors (35%), followed by the inner shelf zone (31%; Figure VI-25). Of subpopulations within the inner shelf subpopulation, percent nonreference was 32% for other mainland and 27% for SPOTWs (Figure VI-26). In the inner shelf zone, nonreference areas were generally found near river mouth areas (Figure VI-27).
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