Population dynamics and stock status of cobia, Rachycentron canadum, caught in Australian recreational and commercial coastal fisheries

Abstract

Abstract Age and growth of Rachycentron canadum (L.) was studied in northern and eastern Australia to provide data for a preliminary assessment of the stock and to explore possible fisheries management strategies using minimum legal lengths. Fish collected from commercial and recreational fisheries ranged in size and weight from 125 to 1633 mm fork length (FL) and 0.031 to 55 kg respectively. Annual growth increments in sectioned otoliths formed by November–December. Estimated ages ranged from 0 to 7 yr for both genders. Longevity was estimated to be at least 13 yr. Von Bertalanffy growth function parameters were L = 1160 mm FL, K = 0.63 yr−1 and t0 = −0.21 yr−1. Rachycentron canadum reach 600 mm FL in their first year and over 1000 mm FL in 3 years. Natural and total mortalities were estimated at 0.35 yr−1 and 0.85 yr−1, respectively. Populations of R. canadum may be vulnerable to growth overfishing under the current minimum legal length of 750 mm total length (TL) in Queensland waters. An increase in minimum legal length to 850 mm TL is recommended.