Impact of derelict fish traps in Caribbean waters: an experimental approach

Fish traps are a widely used fishing gear throughout the Caribbean Sea, but become marine debris when lost or abandoned, with uncertain impacts to coral reef ecosystems. Derelict fish traps are thought to cause fish mortality through unintentional fishing or ghost fishing; yet no scientific studies have been conducted to quantify the threat from ghost fishing in Caribbean waters. Using an experimental approach, 12 unbaited traps were deployed at nearshore and offshore locations in the US Virgin Islands to simulate derelict traps. Six traps were set with escape panels closed (fishing) and six had escape panels open. Frequent underwater visual surveys of fishes inside and surrounding traps were conducted to quantify fish assemblage composition, body size, fish behavior, condition, and mortality over 6 mo. Twenty mortalities (2% of trapped fish observed) were documented. All but one mortality occurred in closed traps with an estimated total market value of US$160 over 6 mo or US$52 per trap annually. Skin abrasions were observed on 34 fishes. A permutational multivariate analysis of variance revealed a significant effect of time on trapped fish assemblages regardless of the location. The results demonstrate that ghost fishing does occur, but that simple modifications to fishing gear such as correctly functioning escape panels will significantly reduce mortality from ghost fishing. Further reduction of impact from derelict traps can be achieved through implementation of land-based trap disposal programs.