Evaluation of eelgrass mitigation and fishery enhancement structures in San Diego Bay, California

To offset habitat loss and increase fishery production, an eelgrass mitigation habitat was completed in San Diego Bay, California in 1997. This mitigation effort consisted of the transplantation of eelgrass, Zostera marina L., in the western portion of the bay. In addition to the establishment of a new eelgrass bed, four enhancement reefs made of either quarry rock or concrete rubble were created to further enhance fishery stocks and the area's ecosystem. Two design criteria and a direct comparison between quarry rock and concrete reefs were examined in this 5-yr pilot program. The newly created eelgrass habitat quickly performed at the level of the existing eelgrass bed. The overall analysis found that the mitigation eelgrass habitat was not significantly different from the reference eelgrass habitat in terms of fishes. Neither reef material (quarry rock or concrete rubble) nor original reef design influenced fish utilization. In addition, aspects of fishery enhancement were examined on the enhancement reefs using three target species of Paralabrax (Perciformes: Serranidae). Resource utilization differed among these congeners with differing levels of production. Using enhancement reefs and eelgrass transplantation, enhancement and mitigation goals were achieved in San Diego Bay.