Distribuição e dieta de tubarões capturados na pesca industrial de a sul de Moçambique

Abstract

The present study aimed to determine the distribution and diet of some shark species in relation to the area, depth, and time of day captured along the southern region of Mozambique in three areas (Boa Paz, Bazaruto, and Banco de Sofala) for experimental fish fishing during 2 llP cruises aboard the R/V FENGUR. The data analysis by depth was done for Boa Paz and by time of day for Boa Paz and Banco de Sofala. 105 trawls were carried out, whose distribution by area was similar between Boa Paz and B. de Sofala. In Boa Paz, 3 depth strips were also sampled. Most hauls were carried out in the morning for both areas. There was a greater number of sharks by trawling in Boa Paz and a smaller number in Bazaruto. Greater number of sharks was obtained at a depth of 20-50m and the number of sharks per trawl was similar in the morning and in the afternoon. 56 sharks corresponding to 14 species, 11 genera and 10 families were captured. The three most abundant species were Squatina africana, Carcharhinus sealei and Loxodon macrorhinus. The total length ranged from 59-87cm, 53-160cm and 53-73cm for African Squatina, Carcharhinus sealei and Loxodon macrorhinus respectively. Where the linear regression results showed for all species an exponential growth. The total density of sharks was higher in Boa Paz compared to B. de Sofala and Bazaruto. The densities of S.africana, C.sealei and L.macrorhinus were significantly different by depth in the Boa Paz area, with S.africana being more abundant in the 100-200m range, C.sealei in the 50-200m range and L. macrorhinus in the 50-200m range. Simple quantitative methods (number, percentage) were used to determine the food composition and degree of overlap of the diets. In both cases, it was found that the species had different eating habits, with a tendency for piscivorous feeding more accentuated in S.africana. The diet of S.africana was essentially composed of fish (77%), (Pagellus natalensis, Decapterus russelli and Saurida undosquamis), of C.sealei by crustaceans (Charybdis ferriata 33.8% and Scyllarides elisabethae 32.3%), and Lmacrhinus of cephalopods ( Sepia pharahonis 35%). It was not possible to identify most fish species in the diet of Carcharhinus sealei and Loxodon macrorhinus species. The verification of the level of exploitation of food resources by the 3 species indicated a biologically insignificant overlap CHmedium = 0.224. (TRADUÇÃO NOSSA)