Breeding season, fecundity, length-weight relationship and condition factor of oreochromis niloticus L. (pisces: cichlidae) in Lake Tana, Ethiopia
1997
Zenebe Tadese (Bahir Dar Teacher's College, Bahir Dar (Ethiopia))
The breeding season, fecundity, length-weight relationship and condition factor of Oreochromis niloticus from Lake Tana, Ethiopia, were studied from monthly samples collected using a bottom trawl between March, 1992 and march, 1993. In Lake Tana Oreochromis niloticus spawns throughout the year, with a high activity between April and August peaking in June and July. The peak spawning coincided with the onset of the rainy season. There was a curvilinear relationship between fecundity and total length (TL) (logF = -0.01 + 2.01 LogTL, r = 0.86, p less than 0.001) and a linear relationship between fecundity and body weight (W) (F = 234.65 + 1.51TW, r = 0.84, p less than 0.001) and gonad weight (GW) (F = 394.55+29.1GW, r = 0.67, p less than 0.001). The length-weight relationship was less than a cube, LogTW = -1.373+2.742LogTL, n=680, r=0.97, p less than 0.001 indicating allometric growth of the fish. the length-weight regression coefficients for both males (2.748) and females (2.747) were almost the same. A significant seasonal fluctuation (ANOVA, p less than 0.001) was observed in the condition of the fish. The relatively low values during April to August may be due to the high energy cost of spawning.
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