Length-Weight and Length-Length Relationships of Heterotis niloticus (Cuvier, 1829) and Raiamas senegalensis (Steindachner, 1870)

Abstract

The sustainable exploitation of freshwater fish species of commercial value is inevitable for fishery to continuously play its role in the social and economic growth of Nigeria. Heterotis niloticus and Raiamas senegalensis are two commercially available species in Lake Alau. The length-weight relationship (LWR) and length-length relationship (LLR) of these species were investigated to determine their growth patterns and state of wellbeing. Fish samples were collected from fishermen landings weekly for four months. The morphometric indices such as Total Length (TL), Standard Length (SL) and Body Weight (BW) were assessed using standard methods. A total of 1583 specimens comprising 602 H. niloticus (51.61% males and 48.39% females) and 981 R. Senegalensis (56.57% males and 43.43% females) were collected. TL ranged from 10.2 to 42.8 cm; 15.5 to 41.6 cm, SL 9.5 to 39.9 cm; 14.0 to 39.9 cm and weighed between 128.50 and 420.14 g; 123.05 and 401.8 cm for H. niloticus and R. senegalensis, respectively. The growth coefficient (b) ranged between 3.127 and 3.340 for H. niloticus and 2.592 and 3.193 for R. senegalensis. This indicates positive allometric growth pattern for the two-species investigated. The LLR varied from 1.511 to 2.148 and 1.506 to 1.820 for H. niloticus and R. senegalensis, with mean condition factor of 2.04 ± 1.76 (H. niloticus) and 1.97 ± 1.98 (R. senegalensis). This study therefore concludes that Lake Alau is favourable to good growth, reproduction, and survival of these species