Estudo da variação espacial e vertical da diversidade e riqueza dos recursos pesqueiros ao longo da Costa de Moçambique

Abstract

The main objective of the present study was to examine the spatial and vertical variation in the diversity and richness of fishery resources along the coast of Mozambique. For the realisation of this study, data collected during scientific cruises of Dr. Fridtjof Nansen carried out in Mozambique’s Exclusive Economic Zone (EEZ) during the periods of February-March 2018 and May-June 2023.The samples were stratified by depth, ranging from 0 to 1000 meters, using pelagic trawls along transects perpendicular to the coast. The data included detailed records of catches, such as the number of individuals, weight, and other species-associated information. Exploratory data analysis was conducted using R software, organising the data into North, Central, and South regions, as well as into depth layers of 0-50 m, 50-100 m, and >100 m. The Shannon-Wiener, Simpson, and Relative Importance Index (IRI) indices were calculated to estimate species composition, determine specific diversity across regions and depth layers, and analyse species dominance by depth stratum. The results indicated that in the southern region, Sepia (21.4%) was the most dominant species, followed by Champsodon capensis (11.8%). In the Central region, the most dominant species were Decapterus russelli (14%), Carangoides malabaricus (11.7%), and Uroteuthis (11.2%). In the North, Sepia and cephalopods such as Loligo were predominant, contributing approximately 21,4% and 10%, respectively. The Shannom-Wiener and Simpson indices indicated balanced diversity among the regions, while species richness was higher in the North and South compared to the Central region.Species dominance varied across the 0-50m depth layer in all regions. In the southern region, Decapterus russelli was the dominant species at depths of 0-50m, followed by Loligo, which stood out at 50-100m, and the family Myctophidae predominated at depths >100m. In the central region, the dominant species were Encrasicholina punctifer at 0-50m, Pelona ditchela at 50-10m, and the family Myctophidae at depths >100m. In the northern region, Decapterus russelli was dominant at 50-100m, and Myctophidae predominated at depths >100m. Therefore, this study contributes to the development of conservation strategies and sustainable use of fishery resources, ensuring the protection of marine ecosystems and the maintenance of their environmental and socioeconomic benefits.