Monitoring fish in California Channel Islands marine protected areas with a remotely operated vehicle: the first five years

In 2003, California established a network of marine protected areas (MPAs) in the northern Channel Islands, offshore of Santa Barbara. In this paper, we analyzed data from remotely operated vehicle (ROV) surveys of fish on deep-water (31-100 m) hard-bottom substrates. We tested the null hypothesis that there is no significant difference in density of target species inside and outside MPAs and also evaluated changes in density over time. The con founding variables water depth and substrate type were controlled by equalizing sampling effort. For the analysis, we used ANOVA with the factors treatment (MPA vs. fished), location of site pair (San Miguel Island, north Santa Rosa Island and southwest Santa Rosa Island) and time (2005 to 2008). Because the main factors were crossed, interactions between factors were used to indicate possible significant effects. Multiple t-tests were used to test for significant treatment effects depending on the type of interaction. Most significant interactions were associated with location. There was only one significant interaction between treatment and time. Using multiple comparison tests instead of averages from the main factors in the ANOVA exposed the underlying variability. No species was consistently more abundant in MPAs than in fished sites at all locations. This study evaluates the first 5 yr after implementation of the MPAs. With additional time, we expect densities to change and the full dimensions of protection should become evident.