The influence of oceanographic conditions on the spatial and temporal patterns of Pleuronectiforms larvae (Teleostei) in the equatorial Atlantic Ocean

Abstract

In this study, we analyzed the composition, distribution and abundance of Pleuronectiform larvae in relation to abiotic factors (temperature and salinity) and biotic factors (phytoplanktonic and zooplanktonic biomass) in the equatorial Atlantic Ocean. The working hypothesis was that the composition and distribution pattern of Pleuronectiform larvae species present differences between the areas studied according to the hydrographical environment/factors analyzed. Ichthyoplankton was collected during Period: 1 (August - October 1995), 2 (January - April 1997), 3 (April - July 1998) and 4 (September - December 2000), in the equatorial Atlantic Ocean. We examined 562 Bongo-net (500 μm) samples that contained 719 Pleuronectiform larvae belonging to three families: Bothidae (Bothus ocellatus and Engyophrys senta), Paralichthyidae (Syacium papillosum, Citharichthys spilopterus and Citharichthys sp.) and Cynoglossidae (Symphurus sp.). The Pleuronectiform larvae accounted for 4% of total fish larvae and occurred at 37% of the oceanographic stations. B. ocellatus was the species with the highest relative abundance (70%), the greatest value occurring during Period 3 (77%), whereas the lowest relative abundance (57%) was recorded in Period 1. S. papillosum was the species presenting the second highest relative abundance (14%), with higher values during periods 1 and 4. The results demonstrated that environmental factors influence the distribution and abundance of Pleuronectiform larvae so that each species occurs in a more favourable period and place for spawning and growth. B. ocellatus was related to warmer waters and greater phytoplanktonic and zooplanktonic biomass, while S. papillosum occurred in saltier waters and at lower temperatures.