Characterizing fish communities associated with drifting fish aggregating devices (FADs) in the Western Indian Ocean using underwater visual surveys
|Other titles||Caractéristiques des communautés de poissons associées aux DCP (dispositifs de concentration de poissons) observés en plongée dans l'ouest de l'océan Indien|
|Author(s)||Taquet Marc1, Sancho G2, Dagorn L3, Gaertner J4, Itano D5, Aumeeruddy R6, Wendling B6, Peignon C7|
|Affiliation(s)||1 : IFREMER, CRH, F-34203 Sete, France.
2 : Coll Charleston, Grice Marine Lab, Charleston, SC 29412 USA.
3 : UR Thetis, CRH, IRD, F-34203 Sete, France.
4 : Ctr Oceanol Marseille, LMGEM, CNRS, UMR 6117, F-13007 Marseille, France.
5 : Univ Hawaii, JIMAR, Pelag Fisheries Res Program, Honolulu, HI 96822 USA.
6 : Seychelles Fishing Author, Victoria, Maha, Seychelles.
7 : UR 109 Thetis, IRD, Victoria, Maha, Seychelles.
|Source||Aquatic Living Resources (0990-7440) (EDP Sciences), 2007-10 , Vol. 20 , N. 4 , P. 331-341|
|WOS© Times Cited||50|
|Keyword(s)||Indian Ocean, Reunion Island, Seychelles, Fish aggregations, Visual census, Drifting FAD, Pelagic fishes|
We adapted a visual census method, mainly used in demersal and reef fish studies, to characterize fish communities associated to drifting fish aggregating devices (FADs) in the Western Indian Ocean. Drifting FAD associated fishes from both equatorial (Seychelles) and tropical waters (Reunion Island) were examined by divers. A total of 32 species (belonging to 16 families) were observed associated with drifting FADs in equatorial waters, and 24 species (14 families) were found around FADs in tropical waters. Twenty species were found in both regions. The highest number of species observed at a single FAD was 18 (12 +/- 2, mean +/- SD) in equatorial and 13 (10 +/- 3) in tropical waters, not counting circumnatant species loosely associated with the FAD. Some species like Kyphosus vaigiensis, Canthidermis maculata, Elagatis bipinnulata, Acanthocybium solandri and Coryphaena hippurus were observed on all or most of the surveys. In this study, the contribution in biomass of the 18 common species associated with drifting FADs (but excluding circumnatant species), represents more than 98% of the biomass. The overall biomass values of closely associated species remains well below tuna biomass estimates for circumnatant tuna schools at FADs, estimated as high as 200 tons. The species that most significantly contribute to the by-catch in tuna purse-seines logically match those that showing the highest biomass values in our surveys (Carcharhinus spp., Elagatis bipinnulata, Coryphaena hippurus, Canthidermis maculata, and Acanthocybium solandri). One of the most abundant and ubiquitous species in our study was the spotted oceanic triggerfish Canthidermis maculata that sometimes formed massive schools of many thousands individuals around the drifting FADs. Future research is needed to explore the role of such non tuna species in the attraction and aggregation processes of tuna around drifting FADs.