Abstract
In this paper the relationship between temporal changes in the occurrence of water masses and Trichiuridae and Gempylidae larvae composition and distribution in the Southwest Atlantic ocean were analysed between 25° and 40° S. Ichthyoplankton was collected during the three expeditions of the Subtropical Convergence Project: Winter and Spring 1977, Autumn 1978 and Summer 1981, realized in the Southwest Atlantic waters. Oblique tows were conducted using a Hensen net with 250 μm mesh size. Steep salinity and temperature gradient were found, where the river outflows from La Plata river (Argentina) and Patos Lagoon (Brazil) met the Tropical Water over the continental shelf between 32 and 36° S. We examined 524 Hensen-net samples that contained about 283 larvae from five species of Trichiuridae and Gempylidae. The most abundant and frequent specie were Trichiurus lepturus Linnaeus 1758 and Diplospinus multistriatus Maul 1948. The mesopelagics species D. multistriatus, Nealotus tripes Johnson 1865 and Lepidopus altifrons Parin&Collette, 1993 were associated with Tropical Water. The benthopelagic T. lepturus and the epipelagic Thyrsitops lepidopoides (Cuvier 1832) were associated mainly with Coastal Water and Subtropical Shelf Water.