Fish Mortalities and Management Measures of Fish Species of the Andoni River, Niger Delta, Nigeria

Abstract

Length-frequency data of 11 fish species sampled from catches of five randomly selected artisanal fishers that use unmotorized canoe were fed into FiSAT (FAO-ICLARM Stock Assessment Tool). The total natural and fishing mortality coefficient result showed that Sarotherodon melanotheron (R.) (2.24 year-1), Galeoides decadactylus (B.) (1.96 year-1), Eucinostomus melanopterus (B.) (1.58 year-1), Tilapia guineensis (B.) (1.44 year-1), Pseudotolithus elongatus (B.) (1.22 year-1) and Ilisha africana (B.) (1.08 year-1) had the highest natural mortality rates and indicative of fast growth (i.e., rapidly approaching asymptotic length (L[infinity])) with the reverse being true for Chrysichthys nigrodigitatus (Lacepede) (0.66 year-1); Pomadasys jubelini (C.) (0.74 year-1); Ethmalosa fimbriata (B.) (0.78 year-1); Lutjanus goreensis (V.) and Liza grandisquamis (V.) (0.87 year-1). The generally high total mortality values of 0.88-3.83 year-1 points to death due not only to legal fishing activities but also great impacts from illegal and obnoxious fishing practices, pollution and environmental degradation and the consequent need for management of this fishery. Management measures should include enforced licensing and registration of fishers and fishing craft, establishment of marine reserve areas and fishing registration centers.