Population Dynamics of Pseudotolithus Senegalensis and Pseudotolithus Typus and Their Implications for Management and Conservation within the Coastal Waters of Liberia

The study evaluated some aspect of population parameters of Pseudotolithus senegalensis and Pseudotolithus typus within Liberia’s coastal waters. A total of 177 and 152 samples of P. senegalensis and P. typus respectively were collected from July to December, 2016. Individual fish samples was measured for standard length and analysed using FiSAT II software. From the results, P. senegalensis growth parameter were estimated at asymptotic length (L∞)=66.68 cm, growth rate (K)=0.13 yr-1, the longevity (tmax)=21.49 years, theoretical age at birth (t0)=-1.586 years and growth performance index (φ')=2.762. While P. typus growth parameters asymptotic length (L∞)=66.68 cm, growth rate (K)=0.14 yr-1, the longevity (tmax)=19.3 years, theoretical age at birth (t0)=-2.126 years and growth performance index (φ')=2.294. Mortality parameters for P. senegalensis and P. typus were calculated as total mortality rate (Z)=0.93 yr-1 and 0.70 yr-1, natural mortality rate (M)=0.37 yr-1and 0.39 yr-1 and fishing mortality rate (F)=0.56 yr-1 and 0.31 yr-1 respectively. The calculated fishing mortality rates (F) compared to Fopt=0.4M were beyond the limit for sustainable fishing. The exploitation rate (E) of P. senegalensis (E=0.60) was higher than the Eopt=0.5 criterion. It implies that P. senegalensis is overexploited while P. typus was at the peak of exploitation (E=0.45). Results from the study revealed that the P. senegalensis fishery in Liberia is slightly overexploited while P. typus is at the optimal level of exploitation; as well as the presence of growth overfishing within the two species population within Liberian coastal waters. Thus, to avert the consequences of growth overfishing, sustainable fisheries measures including monitoring of fishing efforts, and increase in mesh size should be implemented and enforced.