Publication Abstract

Fish morphology and estimatingselectivity by gillnets

E.G. Reis and M.G. Pawson

A fleet of gillnets of various mesh sizes was fished in the PatosLagoon, Brazil, to investigate how measurements of a fish's body can best be used todetermine the selectivity by gillnets. Catch data were analysed for four morphologicallydissimilar species: Micropogonias furnieri and Menticirrhus americanus(Sciaenidae), Mugil platanus (Mugilidae) and Brevoortia pectinata(Clupeidae). Fish enmeshed at several positions along their bodies were used to elucidatethe mechanism by which they are caught in relation to mesh size. Capture was found to bemost efficient when the ratio of the girth at the position where the fish was caught tothe mesh perimeter lies in the range 1–1.1. In these four species, fish with similarmaximum girths in the available length range were most likely to be caught by a net of aparticular mesh size, provided that enmeshing rather than tangling was the main mode ofcapture. In this context, gillnets can be considered to be girth-specific rather thanspecies-specific gears. However, total length is closely related to girth, and bothmeasurements can be used to describe the selectivity of a particular net.

Reference:

E.G. Reis and M.G. Pawson, 1999. Fish morphology and estimating selectivity by gillnets.Fisheries Research, 39(3): 263-273.