Distribution and abundance of fish larvae in the Patagonian Shelf-break Front

Abstract

The distribution and abundance of fish larvae were investigated in three sections across the Patagonian Shelf-break Front, in the Southwest Atlantic, between 44° and 47° S during springtime. Hydrographic sampling covered the shelf edge, slope and oceanic waters down to 3160 m depth. Larvae were collected with a Hydro-Bios Multi-net of 0.25 m² mouth size at 48 stations. Sampling covered the outer shelf, slope and oceanic waters. Each station was sampled during day and night at five depth levels from the surface to 200 m. At each station, temperature, salinity and fluorescence profiles were obtained to characterize water masses and detect the front. The variation in salinity between shelf and Malvinas Current waters was the most obvious sign of the frontal area. Twenty-two different species belonging to 10 orders and 16 families were found. On the outer shelf, were detected larvae of Perciformes and Scorpaeniformes, in low relative abundances. The slope was characterized by the presence of larvae of Myctophiformes and Gadiformes, while in the open ocean area, larvae of mesopelagic fishes such as Myctophiformes, Argentiniformes and Stomiiformes predominated. The highest abundance of larvae was found at the levels closest to the surface in the night stations. This study is the first one to obtain information on the ichthyoplankton composition of the Patagonian Shelf-break Front ecosystem for the austral spring period.