Monitoring biodiversity using ecosystem assessment surveys and regional ocean models within the California Current

The National Marine Fisheries Service has conducted an annual midwater trawl survey for juvenile rockfish and other pelagic micronekton every May and June from 1983 to the present. Although both the spatial and temporal coverage have varied over time, a “core” region has been sampled continuously for the region that extends from Monterey Bay to just north of San Francisco Bay, California. Stations are located from nearshore waters to the offshore environment, but generally within 60 km from land. The mid-water trawl targets a diverse micronekton community spanning a range of juvenile stages of fishes, adult forage fishes and various invertebrates. Here we use the historical catch data to investigate biodiversity across space and time, specifically through developing indices of richness, diversity and evenness. The interannual variability of these indices is coherent over three unique ecological regions located along the shelf, Monterey Bay submarine canyon, and offshore habitats. Spatiotemporal changes in diversity reflect different taxa such as juvenile groundfish, rockfish and forage fish, and influx of oceanic species to nearshore habitat during anomalous years. Finally, data from CTD casts and from a data-assimilative ROMS model links changes in biodiversity with changing environmental conditions. The results of this project will be used to help inform researchers in the creation of a Marine Biodiversity Observation Network (MBON) in the Monterey Bay National Marine Sanctuary.