Growth, mortality, sexual maturity and exploitation of the ribbonfish, Trichiurus lepturus (Linnaeus, 1758) (Pisces: Trichiuridae) in Ghanaian waters

Abstract

The ribbonfish, Trichiurus lepturus is actively and locally exploited by commercial fishers along the coast of Ghana. As a contribution to fill the knowledge gap on this species, size composition, growth and mortality as well as sexual maturity and exploitation of the stocks were assessed. Samples were collected from major fish landing sites along the coast of Ghana from September, 2018 and August, 2019. Length-frequency data were used in the estimation of growth and mortality rates and exploitation ratio. Total lengths of T. lepturus sampled ranged between 24.8 and 103.9 cm with a unimodal distribution of 55 cm. The length and weight relationship established that growth was positively allometric. The asymptotic length (L∞), growth coefficient (K) and age at zero length (to) for T. lepturus were estimated as 133.66, 0.46 yr-1 and -0.88 respectively. Total (Z), fishing (F) and natural (M) mortality rates of were estimated at 2.69 yr-1, 2.03 yr-1 and 0.66 yr-1 respectively. The length at first capture (Lc) was lower than the length at first maturity (Lm). Spawning occurred all year round with a peak spawning period from March to June. Fecundity was estimated to be 17,440 ± 1,250 eggs (mean ± SE). There was no significant difference observed in the sex ratio between males and females. The species showed to be vulnerable to overfishing. There is therefore the need for a reduction in fishing pressure of the stocks to promote proper management of this fishery resource.