Cephalopod paralarvae in a tropical Brazilian basin: distribution throughout oceanographic features and water masses

Abstract

The composition and distribution of cephalopod paralarvae were investigated in the Campos Basin, a tropical area on the southeastern Brazilian continental margin with extensive oil exploration. Zooplankton hauls with a multi-mesh net system were conducted during two seasonal oceanographic cruises in 2009 along eight isobaths (25–3000 m) and vertical sampling in five water mass cores (1–2300 m depth). A total of 825 paralarvae belonging to 11 families and at least 16 genera were captured. The majority had a dorsal mantle length of less than 2.60 mm, with a mean of 1.50 mm. The rainy summer showed higher total densities and number of families compared to the drier winter. Most paralarvae were collected at Surface Water (1 m depth), only four at South Atlantic Central Water (250 m), and two at Antarctic Intermediate Water (800 m). Enoploteuthidae and Ommastrephidae were the most abundant families and were positively associated with temperature, with higher densities during the rainy summer. Loliginidae were collected exclusively in the neritic zone. In the oceanic zone, Cranchiidae, Onychoteuthidae Octopoteuthidae, and Tremoctopodidae were collected at 1 m depth, and Ancistrocheiridae and Thysanoteuthidae at 250 m depth. Density peaks of paralarvae occurred during the summer along the continental shelf break and slope, an area known for frequent upwelling driven by cyclonic meanders of the Brazil Current.