水産および畜産生産

抽象的な

Reproductive Biology of Heterotis niloticus (Cuvier, 1829) in Alwero Reservoir, Gambella, Ethiopia

Ojuni Odier, Minwyelet Mingist, Gashaw Tesfaye and Adamneh Dagne

This study was to investigate reproductive biology of Heterotis niloticus in Alwero Reservoir for better exploitation of fish resources which was conducted on monthly basis from December 2020 to November 2021 to know Length-weight relationships, sex ratios and size at first maturity of H. niloticus. Gillnets of 11 different mesh sizes (4, 6, 8, 10,12,14,16,18,20,22 and 24 cm) were used to sample the fishes. Total Length (TL) and total body weight (TW) of H. niloticus were measured to the nearest 0.1 cm and 1 g, respectively. The results of the study showed that the length-weight relationships for H. niloticus (TW = 10.502TL1.4; n =360; r2 = 0.749) and showed a curvilinear relationship, signifying the fishes growth were negative allometric growth, insignificant difference between sexes (P<0.05). The size at first sexual maturity (L50) for H. niloticus females 56.20 cm TL and 52.57 cm TL for males. H. niloticus have an extended breeding period from March to August, with peak spawning in June and July. The main intense in breeding activity occurred during the rainy months of April to August. The mean numbers of eggs per female were 19,698.5 eggs for H. niloticus, with total length range from 44 to 97 cm TL. Fecundity had a significant correlation (P<0.05) with both somatic weight and total length. Based on growth parameters indicated that the fish population is normal fish population with no apparent problems of over exploitation, although there is report in size reduction of fish by fishers. Unregulated open access resource use, illegal use of gillnets and uncoordinated water resources development activities existed.