The effect of the Jessica grounding on Galapagos reef fish communities adjacent to the wreck site

摘要

The grounding of the oil tanker Jessica off San Cristobal Island, Galapagos, resulted in generally elevated rather than depressed densities of fishes adjacent to the wreck site 15 weeks post spill. Species richness of fishes declined along transects out from the wreck: however, patterns were inconsistent for different depth strata, with the most clearly defined decline evident for the intermediate 5-7 m depth stratum. Fish species attracted to the immediate wreck site, most notably the surgeonfish Prionurus laticlavius, the damselfish Microspathodon dorsalis and the angelfish Holacanthus passer, were considered to be responding either to the heterogeneity provided by the wreck structure or elevated densities of macroalgae. The fish community at the wreck site lay outside the range of variation for other sites investigated in the region; however, contrary to predictions of grounding impacts, the fish assemblage immediately adjacent to the wreckage showed greater faunal similarity to reference sites than did fish assemblage at 60-90 m distance from the grounding.