Alternate Title

Experimental Evaluation of Potential Effects of Habitat Size and Presence of Conspecifics on Habitat Association by Young-of-the-Year Red Snapper


The potential effects of habitat size and the presence of larger conspecifics on habitat association by young-of-the-year (YOY) red snapper Lutjanus campechanus was evaluated in 2.2 m3 laboratory tanks. Our results indicate that YOY red snapper have a strong affinity for structure, which ranged in these experiments from open-sand bottom to concrete-block, artificial reef-like habitats. Mean distance of YOY red snapper from the blocks decreased significantly and the time spent near the structures increased significantly as the size of the habitat increased. However, when larger subadult snapper were present, both distances to the reefs and time that YOY spent near them was significantly reduced, as the larger conspecifics actively defended the structure from occupation by YOY. If similar interactions occur in situ, small snapper that attempt to move onto reefs from the shrimping grounds that serve as nursery areas for juveniles may be subject to predation pressures by piscivorous fishes inhabiting the reefs. Finally, in experiments that used both larger conspecifics and alternate prey similar in size to the YOY red snapper, results indicated that larger snapper preferentially consumed the alternate prey and did not cannibalize the YOY red snapper. Nevertheless, YOY still were not permitted to occupy the artificial reef habitats in any experiments when larger conspecifics were present in the tanks. If results of these experiments are exportable to the field, they may partially explain the observation that YOY red snapper in natural populations are more often found in shallower water on shrimping grounds, whereas larger juveniles begin to recruit to the offshore reefs once they have obtained a size refuge. If additional studies conclude that YOY red snapper are attracted to larger or more complex habitats but avoid these structures because of pressure from larger juveniles and/or adults, the strategy of continued placement of artificial reefs large enough to attract adult snapper and other piscivores in and near the inshore shrimping grounds should be reassessed.