Size structure of the Lebranche mullet (Mugil liza) captured by the ringed gillnet fleet off south Brazil

Abstract

The hereby study evaluated the size distribution of the Lebranche mullet Mugil liza captured by the ringed gillnet fleet using different mesh sizes (8, 9, and 11 cm) during the 2018 fishing season in south Brazil. Analyses compared the size distribution and selectivity coefficients of the three mesh sizes concerning the minimum size of catch and the size of first maturity. Three modal sizes were discerned between the frequency distributions, with females being significantly larger. Males showed a unimodal distribution, while females presented two modes, being the larger one present only in the catches of the larger mesh size. The smallest minimum size and the largest maximum size were recorded in the intermediate mesh size in two landings of the same vessel. The largest mean size occurred in the largest mesh size, showing possible effects of selection. The length frequency distributions best fit a bi-normal selectivity model, revealing the presence of different age classes within the capture. All mesh sizes captured individuals above the size of first maturity, but the probabilities of selection showed different results among mesh sizes. The selectivity coefficients provide insights into optimal mesh size regulations for sustainable fisheries management for Mugil liza off South Brazil.