Swordfish growth pattern in the strait of Gibraltar; implications for Atlantic and Mediterranean stock mixing

Abstract

A growth study of the swordfish in the Strait of Gibraltar was carried out, based on monthly size frequency data collected from the Moroccan driftnet fishery during the period 2006-2011. The growth parameters were estimated by the modal progression analysis (MPA), using both the Bhattacharya and NORMSEP methods. The standard von Bertalanffy growth function (VBGF) for length was found to be: Lt =253.6 [1-exp (-0.17(t + 1.30))]. The growth pattern of swordfish in the Strait of Gibraltar was found to be very similar to that obtained from past studies in various Mediterranean areas. Given the existing growth differences among Atlantic and Mediterranean swordfish, this suggests that the majority of fish caught in this area most likely belong to the Mediterranean stock. However, further studies are needed to identify the degree of stock mixing.