Avaliação da fauna capturada pelas artes de pesca banidas (arrasto e chicocota) no estuário dos Bons Sinais e suas implicações ecológicas pós- regulamentação

Abstract

The study of fauna in periods before and after the enactment of specific legislation in estuarine environments represents a relevant tool for evaluating the effectiveness of the regulation in environmental conservation and the maintenance of fish stocks. This study aimed to evaluate the fauna captured by banned fishing gear (chicocota and trawling) in the Bons Sinais Estuary, comparing the pre- and post-regulation periods. To this end, historical data from sampling carried out by Reno and Simango in 2019 (before the enactment of the law) and data from sampling carried out between 2023-2024 (after the regulation) in the Chuabo Dembe and Icidua fishing centers were acquired. Statistical analyses were performed in Excel, where species abundance and ecological diversity index were determined. Subsequently, the indices were tested using Hutcheson's t-test to assess the significance of the observed difference in the index. The results indicated the capture of 48 species, a figure almost the same as that recorded by Reno and Simango (2019), who identified 47 species in the pre-legislation period. The most dominant species was Penaeus indicus, which represented 55% of the total abundance in 2019 and 33.8% in 2023– 2024. Other commercially important species, such as Sardinella albella, Tryssa vitrirostres, Johnius dussumieri, and Stolephorus indicus, collectively accounted for 30% of the total abundance in 2023– 2024, while Hilsa kelee, Johnius dussumieri, Pomadasys Kaakan, Sardinella albella, Stolephorus commersonii, and Tryssa vitrirostres represented 32% in 2019. The comparative analysis of the biodiversity indices (Margalef, Shannon-Wiener, and Pielou) revealed a significant ecological improvement in 2023, with all indices showing higher values (e.g., H′ increased from 2.43 to 2.73). This result suggests a positive effect of the regulation on species diversity and evenness. However, the analysis of the population structure demonstrated that the highest frequency of capture for most high-value commercial fish species (Mugil cephalus, Johnius dussumieri, Pomadasys kaakan) occurs at sizes significantly smaller than the length at first sexual maturity (Lm), highlighting the mass capture of juveniles. For Penaeus indicus, the predominant capture of subadults in the estuary, while optimizing immediate fishery yield, interrupts its life cycle before recruitment to the marine spawning stock. The results underscore the low selectivity of the prohibited gears and suggest the persistence of these practices, despite the regulation in force."