Study of the fisheries biology of Atlantic thread-herring, Opisthonema oglinum , in Cascavel county, Ceará State, Brazil

Abstract

The Atlantic thread-herring, Opisthonema oglinum, is a species of the family Clupeidae. In Ceará State, it exploitation spans the entire coast throughout the year, with the best harvesting period occurring from May to December.  The present work was designed to study the fisheries biology of this species off Caponga Beach, in Cascavel county. In order to obtain data on length and weight 1,200 specimens were sampled from March through August, 2012. For the investigation into the selectivity of the fishing gear 240 specimens were sampled in July with 5.0 cm- and 5.5 cm-meshed gill nets with the same procedure being repeated in August. The collected data were displayed in scatter plots of weight and length distributions, where the 86.8 g and 22,3 cm classes were shown to be the most representative with 27.83% and 31.5% of their respective frequencies. The equation that represents the weight-length relationship was Y = 0.0081 X 3.0028.  Gill nets with 5.0 cm and 5.5 cm mesh sizes display a very low probability of catching individuals below the minimum landing size, and thus have a great importance for the sustainability of the stock of Atlantic thread-herring in Cascavel  county, Ceará State.