Palos Verdes Reef: A test of artificial reef design criteria to increase regional fish production in southern California

The first offshore and in situ restoration rocky reef in California, the Palos Verdes Reef (PVR), was designed to maximize the secondary production of fishes. The overall project goal was to restore 35.2 ha of sediment impacted or buried rocky reef utilizing 52,729 mt of granitic quarry rock modules distributed strategically with a footprint of 3.2 ha. Module design, modeled after a nearby highly productive natural reef feature, incorporated relief and rock size criteria to theoretically withstand sedimentation and turbidity impacts. In a first for temperate reef ecosystems, reefing modules were placed adjacent to the natural reef. Further design criteria included maximization of ecotonal perimeter and soft-bottom halos increasing niche and resource availability. Postconstruction, we documented the relocation of resident reef fishes from surrounding reefs to the newly created habitat. From 2021 to 2023 for reef associated fishes, standing biomass and secondary annual production increased across all modules: total fish biomass increased from 223 to 3286 kg (1372%) and production increased 59 to 690 g m −2 yr −1 (1062%). Halo biomass density increased; from 6.9 to 22.5 g m −2 and production density from 1.8 to 6.0 g m −2 yr −1 . Due to their relatively large area, overall halo production was nearly equivalent to module production. Over the entire restoration site, fish biomass increased 96% and production increased 93%, demonstrating its carrying and productive capacity was almost doubled during the initial three-year period post-construction PVR modules. These metrics of strong success occurred while the system is still developing, despite declining biomass and production at reference sites.