Juveniles and undersized fish in small-scale fisheries: gillnets are not less implied than trawling

Abstract

Of particular concern in commercial fishing catch is ‘size bycatch’, i.e. the death of early stages of resources that would reach a marketable value when they turn into adults. This event is frequently associated with trawling because of the lower size selectivity of this gear as compared to gillnets. However, this is expected when small-scale fisheries (SSF) employ gillnets simultaneously in setnets + driftnets that mix multiple mesh sizes. This work analyzes fishing captures and compares characteristics of fish catch from gillnets and trawlers with respect to size at first maturation, legal size of capture, and expected discards. Data were obtained from 2007-2021 for SSF in Southern Brazil. A total of 112 fish species were represented in the data. Gillnets exploited fewer species than trawlers; however, most of these constitute fishing resources in the study region. Of the 19 species whose maturation size is known, nine occurred in gillnets as juveniles, and of the 14 species for which the legal size of capture is established, seven occurred in gillnets in prohibited sizes. Gillnets and trawlers presented size bycatch and affected different species between them, with four resources that were present in bycatch from both gillnets and trawlers. The broad range of mesh sizes employed by SSF warns of the discarding of undersized captures, and stresses the importance of policies addressing gillnet management.