Estudo da distribuição vertical e horizontal da lula Ommastrephes bartramii na Costa de Moçambique

Abstract

Ommastrephes bartramii is an oceanic cephalopod widely distributed in subtropical and temperate waters of the Pacific, Atlantic and Indian Oceans. It is an important component of marine ecosystems and a target of fisheries in several regions of the world. The main objective of this study was to describe the vertical and horizontal distribution of O. bartramii along the coast of Mozambique. The data were provided by the Oceanographic Institute of Mozambique (InOM) and were collected with the benthic trawl net during the scientific cruise Dr Fridjof Nansen. The expedition took place during the months of May and June 2023 along the southern and central regions of the Mozambican coast. This database contained information on depth and position of capture, date and time of fishing and the diversity of species sampled. ArcGis version 10.1 was used to produce spatial distribution maps and Microsoft Excel was used to produce vertical distribution graphs, population structure and analysis of first maturity size. The spatial and vertical distribution showed that most of the biomass was concentrated in the latitudes 20oS - 24oS and longitudes 35oE - 36oE, corresponding to the Inhambane coast, and the lowest biomass in the latitudes 24oS - 26oS and longitudes 32oE - 35oE on the Gaza and Maputo coasts, where most of the biomass was juveniles and was found at depths between 0±50 metres and the adults at depths greater than 150 metres. Statistical analysis showed that the squid caught during the study period had not yet reached the first stage of maturation, i.e. the sample and theoretical means show significant differences (t=6.235, p-value<0.05) at 95% confidence level. The study, although preliminary, suggests that the sampling period (May-June) is not suitable for fishing O. bartramii on the southern coast of Mozambique, however additional information from the sampling period is necessary to provide consistent results to outline conservation and management strategies for the resource.