Mesh size selectivity of drift gillnets for skipjack tuna (Katsuwonus pelamis) in Gulf of Oman

In this study, gillnet selectivity of skipjack tuna (Katsuwonus pelamis) is determined for the data came from Oman sea in south-east coast of Iran during 2017-2019. For this purpose, girth measurements for opercular (OP) and front of dorsal fn (D1) of the nets with stretched mesh sizes of 140 and 146mm were incorporated into the theoretical selection curves based on cumulative function of standard normal distribution. Analysis of covariance (ANCOVA) showed that girth at D1 is determined as a maximum girth of skipjack tuna. Data on capture process showed that most fish is enmeshed by the nets, and hence it justifes the use of the selectivity model. The selectivity curves were in consistent with length distributions and the optimum selection length was estimated at 53 and 55 cm for 140 and 146 mm nets, respectively. The fndings of the present papers suggest that the commonly used drift gillnets are not destructive for skipjack in terms of size selection, as most fsh are allowed to spawn at least once before capturing. More issues on skipjack fshery management in Indian Ocean are discussed.