Bejarano et al. 2011

scientific chapter | Proc Gulf Caribb Fish Inst | open access

Use of Mixed-gas Rebreathers to Access Fish Assemblages in Mesophotic Coral Ecosystems (MCE) off La Parguera Shelf-Edge, Puerto Rico

Bejarano I, Nemeth M, Appeldoorn RS


Diver-based visual census is commonly used to evaluate reef fish communities for ecological and fisheries purposes but depth limits to conventional scuba (~30 m) could bias the data. Fishes from Mesophotic Coral Ecosystems (MCEs) are important to scientists and managers because it is thought that these assemblages (1) contain the lower distribution of many shallow species, (2) contain additional commercially important species limited to these depths, and (3) are difficult to assess using other technologies due to the extreme geomorphology of slope environments. This study surveyed the fishes associated to six MCE sites off La Parguera from 50 to 85m depth, using rebreather trimix technical diving. Seventy-five fish species were identified in 64 transects and 30 species in 60 roving surveys. This rich ichthyofauna includes both common inhabitants of shallow reefs and species confined to deep habitats. MCEs are dominated by zooplanktivores (one-third of species; 63% of abundance) while herbivores dominate shallow reefs. Surveys found a higher abundance of fishery commercial species compared to shallow reefs, suggesting that MCEs serve as refugia for heavily exploited fishes. Depth and topographic complexity could shape MCEs assemblages; there is a greater abundance of zooplantivores and fishery-exploited species at more rugose sites. Research and monitoring of MCE fish assemblages are critical to enhance our knowledge on species composition and to compare ecological processes with shallow reefs.

Depth range
50- 85 m

Mesophotic “mentions”
54 x (total of 2523 words)

Methods and Technology


Puerto Rico


Author profiles
Ivonne Bejarano ( 6 pubs)
Richard Appeldoorn ( 10 pubs)