Growth and exploitation rate of Common cuttlefish, Sepia officinalis in Ghanaian Coastal Waters

Abstract

This study presents a preliminary assessment of growth and mortality parameters for Sepia officinalis along the coasts of Tema, Sakumono, and Ningo-Prampram, Ghana. A total of 264 specimens were purchased randomly from fishermen between January and December, 2020. Samples obtained were measured for mantle length and analyzed for growth and exploitation rates using TropFishR software. The mantle length of the species ranged from 3 cm to 26.7 cm with a mean mantle length of 12.4 ± 0.4 cm. Mantle length–frequency data fitted to the von Bertalanffy Growth Function yielded an asymptotic length (Linf) of 30.23 cm, a growth coefficient (K) of 0.57 year⁻¹, and a longevity of 5.0 years. Mortality estimates revealed total mortality rate (Z) of 1.14 year⁻¹, natural mortality rate (M) of 0.89 year⁻¹, and fishing mortality rate (F) of 0.25 year⁻¹, with an exploitation rate (E) of 0.22. The lower fishing mortality rate reflects low commercial demand for S. officinalis in among artisanal fisherfolk in Ghana. The exploitation rate demonstrates that the species in the coast of Ghana is underexploited, though at a sustainable level. Nevertheless, as a precautionary management measure, fishing effort should be monitored to ensure that biological reference points for sustaining this species are not exceeded.