Abstract

Effects of shrimp trawling on life history parameters and production potential were evaluated for juvenile red snapper (Lutjanus campechanus) in the northern Gulf of Mexico (GOM). In addition, the effects of trawling on the associated fish and invertebrate communities and their habitats were investigated. Quarterly trawl surveys were conducted over a two year period on sand and shell-rubble habitats in conjunction with concomitant remotely operated vehicle (ROV) transects used to quantify habitat characteristics. Similar habitats both within a de facto non-trawl area, and outside of the area where commercial shrimp trawling occurred, were used to evaluate the impacts of trawls. Red snapper collected over sand and shell-rubble areas exposed to trawling exhibited slower daily growth rates in the fall, experienced higher mortality rates, had lower G:Z ratios, and had truncated size distributions when compared to similar habitats in the non-trawl area. In addition, lower numbers of both age 0.5+ (180-364 d) and age 2 and above (730+ d) red snapper were collected in trawled areas. Results of the habitat characteristics and their influence on the biotic community showed that structural characteristics were important for structuring shell-rubble communities and were influenced by the presence of trawling. The highest total number of fish and invertebrates were collected over the non-trawled sand habitat and both evenness and diversity were highest over non-trawled shell-rubble habitat. Length-frequency distributions indicated a truncated size distribution of the most influential fish species characterizing the communities over trawled habitats when compared to similar non-trawled habitats. This study demonstrated the negative effects of commercial shrimp trawling on red snapper demographics as well as the biological community and the associated habitat over the continental shelf of the northern GOM. We suggest juvenile red snapper production and the associated ecosystem may benefit from shrimp non-trawl areas on the northern GOM shelf

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