Competitive interactions between gray triggerfish (Balistes capriscus) and red snapper (Lutjanus campechanus) in laboratory and field studies in the northern Gulf of Mexico

Abstract

Field removal and laboratory studies examined competitive interactions between gray triggerfish (Balistes capriscus) and red snapper (Lutjanus campechanus). In field studies, all gray triggerfish and red snapper were counted and sizes estimated on 24 reef sites. Gray triggerfish were then removed from half of these reef sites, resulting in significantly fewer gray triggerfish on the removal reefs at the start of the experiment. After 7 months the experiment ended and reef sites were resurveyed. Gray triggerfish decreased on both treatments, while the mean number of red snapper did not differ between treatments; however, there were significantly more small (<400 mm total length) red snapper on reefs where gray triggerfish were removed. In seven laboratory growth trials (30 to 35 days each), red snapper held with gray triggerfish had significantly lower growth rates and numerous bite marks compared with red snapper alone. These competitive interactions indicate that management efforts to rebuild and increase gray triggerfish populations may have unintentional negative effects on red snapper populations, particularly for smaller fish.