Abstract

Mesophotic ecosystems (30-150 m depths) are poorly understood due to the inherent difficulties associated with working below recreational SCUBA diving limits. Nonetheless, baseline studies of the community structure, biodiversity and, geographic connectivity of mesophotic reef habitats are essential with increasing threats from climate change, ocean acidification, and invasive species. Multibeam sonar, side scan sonar, and ROV technologies were used in this study to examine the fish communities of two mesophotic ecosystems in Northwestern Gulf of Mexico: North Hospital (27°34'30”N, 96°28'30”W) and Hospital (27°32'30”N, 96°28'30”W) banks. These banks are remnant structures of a relict coral reef paralleling the South Texas shoreline that was extant during the late Pleistocene. Reef fish were identified and enumerated from ROV transect video footage. Side scan sonar was used to quantify water column fish aggregations along transects at each reef site. Collectively, forty species in 20 families were identified including invasive Pterois volitans. North Hospital’s reef fish community had higher species richness (S = 38) and Shannon’s diversity (H’ = 1.94) compared to Hospital (S = 18 & H’ = 1.46). The reef fish communities were 97.5% dissimilar. The three most common species at Hospital Bank were Lutjanus campechanus (32%), members of the family Gobiidae (23.6%), and Lutjanus griseus (7%). The three most common species at North Hospital Bank were Chromis insolata (46.6%), Chaetodon sedentarius (7.4%), and L. campechanus (7%). Approximately 3.5 times more fish were observed per km in ROV and sonar transects at North Hospital than Hospital. Side scan sonar indicated that the majority of fish abundance occurred in high slope areas at 11-20m below the reef crest at both banks.

PDF Preview