| dc.description.abstract | The relative abundance, distribution, feeding ecology and
the reproductive biology of the blackbass, Micropterus salmoides
(Lacepede) in Lake Naivasha are described. Blackbass population
is low as compared to that of the tilapiines in the lake. Depth
is the major parameter affecting the distribution of the species,
the numbers decreasing with increase in depth ( r= -0.89. P >
0.05).
The food habits of the species changes with the size of
the fish. In order of importance, juvenile blackbass feeds on
corixids, chironomids, young crayfish, fish fingerlings and
aquatic weeds while the adults feed on crayfish, fish
fingerlings, corixids, frogs, chironomids. aquatic weeds and
beetles. The frequency of occurrence of crayfish and fish
fingerlings in the stomach of the adult was almost equal. There
was a positive correlation between the size of the blackbass and
the size of the prey eaten (r = 0.900, P < 0.001). M. salmoides
is a diurnal feeder but shows increased feeding activity at dawn.
around noon and towards dusk. Monthly variation in fullness
index showed active feeding from August to-February.
salmoides in Lake Naivasha has a single breeding
period which extends from August to January. This period is
characterized by the presence of highest numbers of mature male
and female fish in monthly catches as well as high gonadosomatic
index. The minimum size at sexual maturity for females occurred
at a size-class of 30 - 34.9 em while males mature at an early
size-class of 25 - 29.9 em. The numbers of males to females in
the population did not differ significantly from the expected 1:1
ratio (X2 = 18.876, P < 0.100). Fecundity ranged from I, 300
eggs to 3.524 eggs with a mean of 2.203 eggs. There was a
positive corrv.ation between fecundity and : (L) body weight
(r = 0.92) and (Li ) ovarian weight (r = 0.89). A negative
correlation was observed between fecundi ty and: (i) body length
(r ~ 0.06) and (ii) egg diameter (r = -0.98).
The equation for length - weight relationship revealed
that growth in M. salmoides i s allometric. Males showed better
condition than females. Condit ion and feeding acti vi ty were
highly correlated (r = 0.84). There was low incidence of
nematode {Contracaecum sp~ infestation in M. salmoides | en |
