Influence of a shipwreck on a nearshore-reef fish assemblages off the coast of Rio de Janeiro, Brazil

Abstract

The effect of the Orion shipwreck on fish assemblage distribution near the reef was studied to the northeast of Rio de Janeiro with six different fishing gears: gillnets, mid-water longlines, circular traps, rectangular traps, vertical longlines, and bottom trawling. The study consisted of a pre-monitoring survey four months before the shipwreck in the area (A) and in two control areas (B and C). After 36 months, a total of 56 species were caught in the Orion reef area, 49 in control area B and 59 in control area C. The similarity analysis, considering the number of fish caught during the nine surveys in the three study areas, clustered the pre-monitoring and first post-settlement surveys of the three sites. This occurred due to the low number of fish captured and the dominance of Trichiurus lepturus and Lagocephalus laevigatus. These results differed from all the other studies in the three areas due to the co-dominance of Ctenosciaena gracilicirrhus and Stephanolepis hispidus. Such spatial similarity shows the low influence of the Orion reef in the area after three years. Biomass values were 15% higher in the Orion reef area than in the control areas, representing an increase of up to 1.2 times in wet weight. The increment of fish communities is still insufficient for proposing sustainable fishery activity in the shipwreck area. The monitoring time (32 months) after the sinking of the Orion may be considered too short to assure that the wreckage had reached its maturity as an artificial reef, either as a fish attractor or producer.