Age, growth and mortality estimates for the ridge-scaled grenadier Macrourus carinatus (Günther, 1878) in the south-western Atlantic

Abstract

In light of their life-history characteristics, deep-sea fishes display a higher vulnerability to overfishing than most other groups of fish, and their exploitation may not be sustainable even at low levels. In the Falkland Islands, increasing efforts have been made to target deep-sea species, such as the ridge-scaled grenadier Macrourus carinatus, in the waters off the continental slope. Research findings relating to the age and growth of this species remain conflicting, largely as a result of non-representative sampling of the population, inappropriate ageing methods, and the absence of age validation. We show how M. carinatus display life-history characteristics typical of the deep-water fish community, such as a long life (53 years), late age at maturity (females = 14.00 years; males = 12.28 years), slow growth and low levels of natural mortality (females = 0.104 year−1; males = 0.117 year−1) that highlight the susceptibility of M. carinatus to overfishing. In particular, validated age estimates obtained using improved ageing criteria indicate that longevity is up to 28 years greater than previously reported estimates. M. carinatus were shown to be sexually dimorphic in size, with females growing larger (females = 31.49 cm pre-anal length [PAL]; males = 24.97 cm PAL) compared to males. Updated biological parameter estimates indicate M. carinatus are far more vulnerable to fisheries exploitation than previously thought. A precautionary approach must be followed and conservation measures put in place to ensure sustainable management of a directed fishery or bycatch of M. carinatus and other similar deep-sea species.