Abstract:
Minor cyprinids are a term loosely used to
describe those members of the family Cyprinidae which do not
grow to a large size.
In this study the biology of minor cyprinid
species of five reservoirs were investigated. The minor
cyprinid species encountered in the reservoirs were
Amblypharyngodon melettinus (Valenciennes), Barbus chola
(Hami1ton-Buchanan), B .dorsali s (Jerdon), B.filamentosus
(Valenciennes), B.sarana (Hami1ton-Buchanan) and Rasbora
daniconius (Hami1ton-Buchanan).
The study was undertaken to provide information
that would be hopefully usefull for initiation and
sustenance of a fishery for these small cyprinid species in
reservoirs in Sri Lanka.
The aspects studied were species composition and
i
aspects of the biology of individual populations viz. length
composition, length-weight relationship, sex ratio, size at
maturity, distribution of eggs in mature gonads, fecundity,
seasonal variations in gonadal stages and GSI, relative gut
length and diurnal activity and feeding.
Differences in the minor cyprinid fauna were
encountered. The most significant being the absence of
B.filamentosus from all the reservoirs except Murutawela
which is deep and mesotropic, and have flow characteristics
similar to a river. Also A .melettinus was very rare in
Murutawela and B .chola was not recorded in Ridiyagama where
the water level fluctuations are minimal.
The overall sex ratio of the different species
differed between reservoirs. Such as for example the overall
male to female sex ratio varied from 1:1.05 to 1:2.13 in
B .chola and from 1:0.77 to 1:1.31 in B .sarana. In general,
in A .melettinus, R .daniconius and B .chola the percentage of
ma les decreased with increasing size whereas in
B.filamentosus it increased with increasing size.
The mean size at maturity of the minor cyprinids
also differed between reservoirs. For example the Uat of
B .dorsalis varied from 82 to 115 mm and of B .sarana from 126
to 145 mm.
The main probable spawning season for each minor
cyprinid species in each reservoir was deduced from studies
of gonadal maturation and changes in GSI. In general the
main spawning season of most of the species coincided with
the rainy season such as for example in B .chola,
B.filamentosus and R .daniconius. In A .melettinus it
coincided with rainy season as well as with reservoir water
level and in B .dorsalis with reservoir water level but not
with the rainy season.
There is no evidence to believe that the minor
cyprinids spawn in the reservoirs. Perhaps they undertake
spawning migration to streams and rivers.
In minor cyprinids the length of the gut varied
mean relative gut length
between the species. In most of them the (mRGL) tended to
A
increase with increasing body size. In general the diel
activity pattern of most of the minor cyprinids tended to
increase with the onset of darkness which did not apper to
be in agreement with their feeding rhythm.
