Abstract:
This study was undertaken to assess some biological aspects of Labeo niloticus; Synodontis schall and Auchenoglanis occidentalis, it was Length-weight relationship, condition factor, Gonadal maturation, Ganado-somatic index and sex ratio as well as to determine the main spawning season, in Upper Atbara and Setit Dams, from September 2019 to January 2020. Samples of fish were collected monthly for a 5 months period. A total of fourteen seventy five specimens of L. niloticus (500 samples), S. schall (five hundred samples) and A. occidentalis (475 samples).The fish specimens used for the study were obtained from fishers operating along Upper Atbara and Setit Dams.Length-weight relationship of studied fish speciestothe total, spinal, standard length and the value of the regression coefficient (b) for L. niloticus,S. schall, and A. occidentalis in the study area were found to be 2.848, 2.838, 2.832; and 2.619, 2.700, 2.651; and 2.823, 1.801, 2.854, respectively with highly significant correlation (r) vary between 0.974, 0.983; and 0.902, 0.907; and 0.724, 0.906 respectively. This indicates allometric growth pattern (b≠3).Very high condition factor values were recorded for L. niloticus,S. schall, and A. occidentalis during the study period; the condition factor's value fluctuated between 3.048, 3.241; and 2.543, 3.253; and 2.151, 2.484, respectively, with an average of 3.12, 2.902; and 2.366, respectively.All collected samples of L. niloticus during this study appear immature. While S. schall exhibited 8.3% maturing. For A. occidentalis spawning season maybe coincided with S. schall spawning season. Two peaks of Ganado-somatic index (GSI) of L. niloticus female were observed in the present study. Simultaneously, the decrease of GSI of S. schall female was observed. Fluctuated GSI value between increase and decrease for A. occidentalis female observed in this study resembles spawning pattern S. schall (stated above).Sex ratio of males to females of L. niloticus, S. schall,andA. occidentalis in the study area was 1:1, 1:1, and 1:09, respectively.
