Effects of a De Facto Marine Protected Area on Decadal Trends in Nearshore Fish Abundance

Biologists have been monitoring the abundance of shallow-water fishes near the Diablo Canyon Power Plant in San Luis Obispo County since 1977 using subtidal visual transects. The studies were designed to monitor impacts from the DCPP thermal discharge, which began full 2-unit operation in 1986. In addition to serving this primary purpose, the monitoring data has been useful for documenting other long-term changes, including apparent declines in the 1990s that were concurrent with sharp increases in the live-fish fishery in the Morro Bay-Port San Luis area in species targeted by the fishery. The events of September 11, 2001 led to the immediate establishment of a no-entry security zone around DCPP that precluded all commercial and recreational fishing along this 2-mile stretch of rocky coastline. We have been able to track the recovery of some fishery species within this de facto marine protected area that has now been in place for over 10 years. These responses to changes in fishing pressure have occurred while the plant has continued operation.