Using Spatially Explicit Data to Evaluate Marine Protected Areas for Abalone in Southern California

Abalone populations have declined dramatically in southern California. The white abalone (Haliotis sorenseni) is now (2001) on the federal endangered species list. To aid in the restoration of white, pink (H. corrugata), and green abalone (H. fulgens), productive marine protected areas need to be selected. We used spatially explicit fishery data (1950-1995) to identify the most productive marine areas in southern California. To assess the role of existing marine protected areas we compared fishery-independent data (1983-2001) inside protected and fished areas. San Clemente Island produced the greatest cumulative catches of white, pink, and green abalone, the most white abalone per hectare of deep reef (25-65 m), and the most green abalone per kilometer of rocky shoreline. Santa Barbara Island, however, produced 10 times more pink abalone per hectare of kelp canopy, making this area an excellent candidate for restoration and protection. Pink abalone surveyed in the Kelp Forest Monitoring Program were most abundant at three sites surrounding Anacapa Island: (1) protected, (2) protected but less visible, and (3) fished. The protected sites, despite having lower abundances of pink abalone initially (1983), had significantly more abalone (H = 9.0; df = 2; p = 0.011) than the nearby fished site over time. Size-frequency distributions revealed that the protected site had more (30%) commercial-size abalone (≥158 mm shell length) than the less visable site (6%) or the fished site (2%). Mean size was significantly larger at the protected site, yielding the highest estimate of biomass and potential egg production (2555 million eggs/site/year) of all the sites. Marine protected areas need to be selected and enforced so that abalone-restoration efforts can be enacted before remnant populations die. Restoration sites for a wide variety of depleted species can be selected based on previous levels of productivity identified by spatially explicit data.