Exploitation and Mortality of the West African Fiddler Crab (Uca Tangeri) in Mbo River, Niger Delta, Nigeria.

Abstract:

Studies on the exploitation and mortality of the crab Uca tangeri in Mbo river of Akwa Ibom State, Nigeria, was conducted for 12 consecutive months. Exploitation was calculated to be -1.62. The negative value could imply that the species is not fished or under-fished Length-frequency data was analyzed using FISAT software. Using the Shepherd’s method, asymptotic length (L∞) was 3.99cm, while the Von Bertalanffy Growth Function (VBGF) K was 0.10. Meanwhile, Powell-Wetheral plot estimated asymptotic length (L∞) was 3.58cm and Z/K was 0.72yr-1. The natural mortality(M) of Uca tangeri was 0.71yr-1. However, using length-converted catch curve, total mortality (Z) was estimated to be 0.27yr-1. The instantaneous fishing mortality (F) was calculated to be -0.44yr-1, indicating that it was not a highly fished species.