The influence of the environment on the variability of monthly tuna biomass around a moored, fish-aggregating device
|Author(s)||Doray Mathieu1, Petitgas Pierre1, Nelson Laetitia2, Mahevas Stephanie1, Josse E3, Reynal Lionel2|
|Affiliation(s)||1 : IFREMER, EMH, F-44311 Nantes 03, France.
2 : IFREMER, Lab Ressources Halieut Antilles, F-97321 Le Robert, Martinique, France.
3 : IRD, US Acoust Halieut, Ctr IRD Bretagne, F-29280 Plouzane, France.
|Source||ICES Journal of Marine Science (1054-3139) (Oxford university press), 2009-07 , Vol. 66 , N. 6 , P. 1410-1416|
|WOS© Times Cited||9|
|Keyword(s)||Lesser Antilles, tuna, environment, geostatistics, biomass estimation, fish aggregating device|
|Abstract||Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided highresolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FADassociated fish biomass, with a sampling error of 27%. Environmental variability was summarized by a small set of principal components (PCs) derived from profiles of temperature, salinity and dissolved oxygen vs. depth; and maps of chlorophyll a derived from remotely sensed, sea-surface colour. A generalized linear model was used to relate tuna biomass to environmental PCs and revealed a positive correlation between tuna abundance and: i) a micronekton layer sensed at 38 kHz and potentially consisting of preferred prey at about 180 m depth; and ii) low subsurface salinity (6080 m). These favourable environmental conditions may be related to thepresence of North Brazilian Current eddies that migrating tuna follow when not temporally associated with the FADs.|