Abstract:
Changes in fish species composition and abundance i
n Lake Naivasha were investigated monthly for a
period of 12 months. Data were obtained both from e
xperimental surveys as well as commercial fish
landings. The structure metrics considered included
species abundance and composition, length-
frequency and physico-chemical attributes. Results
of the study showed that the fishery is currently
dominated by the recently introduced common carp,
Cyprinus carpio
accounting for over 95% of the
total fish landings, with the naturalized fish popul
ations performing dismally both in terms of
abundance as well as health conditions. The entry o
f the common carp into Lake Naivasha may have
completely transformed the lake’s ecosystem integri
ty, driving the initially abundant tilapiine specie
s to
near local extinction. The study also confirms a re
stricted distribution of
Micropterus salmoides
to
rocky-bottomed habitats of Hippo Point and Crescent
Lake. Conversely, the long-fin barb,
Barbus
paludinosus,
initially confined to the north swamp and the mout
h of River Malewa, currently exhibits a
lake-wide distribution. The changing climatic condi
tions as manifested in the lake level recessions ma
y
be a real threat to the fish stocks in the lake. Hu
man activities in the catchment areas may also have
contributed to the recent ecological changes witnes
sed in Lake Naivasha. This study proposes a
number of recommendations with a view to ensuring e
cosystem integrity and consequent sustainable
fisheries of Lake Naivasha.
