LENGTH-WEIGHT RELATIONSHIP, BODY CONDITION AND SEX RATIO OF TILAPIA (OREOCHROMIS NILOTICUS L.) IN LAKE CHAMO, ETHIOPIA

Abstract

The length-weight relationship of 1429 fish ranging in
size from 120 to 610 mm Total Length (TL) and from 36 to 4800 g Total
Weight (TW) w<\s computed based on monthly samples collected
between March 1996 and Ma,rch 1997. Th~ relationship between total
length and b?tal weight for both sexes was curvilinear and statistically
significant. The regr~ssion equation for the females was
TW=0.0225TL2-97 r2==0.98, P<O.05 and that for the males was
TW=0.0211TL2-99 r2=0.98, P<0.05. There was a significant variation in the
mean monthly condition factor of both sexes (ANOVA, P<0.05). The mean
± SE Fulton's condition factor ranged from 2.10 ± 0.03 to 2.35 ± 0.10 for
the males; from 1.96 ± 0.03 to 2.1 ± 0.04 for the females. Sex ratio of O.
niloticus was not sigrrificantly different from 1:1 in the total samples.
However, numerically females were significantly more (P<0.05) in
number than males in samples taken between March and May whereas
males dominate in samples taken between October and February. There
was also a significant variation in sex ratio in samples of fish larger than
400 mm TL and dominated by males (P<O.05). However, sex ratio did
not deviate significantly from the theoretical ratio 1:1 (p>0.05) in
samples of fish less than 400 mm TL.