A comparison of finfish assemblages on subtidal oyster shell (cultched oyster lease) and mud bottom in Barataria Bay, Louisiana

Recent research suggests that oyster reefs provide unique three-dimensional hard bottom habitat for many fish species. Along the northern shore of the Gulf of Mexico, oyster shell bottoms are predominantly flat, subtidal and cultched, lacking the vertical relief and spatial heterogeneity provided by natural reefs. This study compared finfish assemblages, gut contents, and macroinvertebrate assemblages at subtidal oyster shell (cultched oyster lease) and mud bottoms in Barataria Bay, Louisiana. Three mud and three shell sites were sampled on seven dates from October 2001 to October 2002, using gill nets and substrate trays. Data from the gill nets were used to compare fish assemblages, as well as to document feeding habits through gut content analysis. Data from the substrate trays were used to document benthic fish and invertebrate communities associated with the two bottom types. Finfish abundance was greater at shell (N = 234) than mud (N = 179) bottoms. Substrate trays collected significantly greater numbers of benthic fishes (p = 0.001) and decapod crustaceans (p = 0.001) at shell bottoms. Gut contents showed predation on fishes, bivalves, and decapod crustaceans. These results show that cultched shell bottoms support a more abundant finfish assemblage than mud bottoms, and provide a potentially important food source for transient fishes due to abundant benthic fishes and decapod crustaceans