Abstract

A recently completed survey of the Lesser Antilles pelagic ecosystem used a combination of multi-frequency acoustics and pelagic trawling to locate and estimate the biomass of forage species. Stratified zig-zag transects covered the waters east and west of the Lesser Antilles from Antigua to Trinidad. The acoustic data were grouped into nine broad categories based on the multi-frequency returns considering backscattering strength, aggregation appearance, depth and time of day. The spatial variation of these broad categories displayed several distinct patterns. There was an inshore-offshore segregation of some groups throughout the survey area, but there was little sign of latitudinal gradients in distribution of these broad groupings. In the open pelagic waters, diel vertical migrations were observed by several identifiable acoustic categories, particularly mesopelagic fish (largely Myctophormes and Stomiiformes), and squids. Dusk and dawn vertical excursions were observed daily between depths from 500m to less than 100m

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