Abstract:

Adjustments in fish species diversity, prey selection
and life history characteristics of Nile perch, Lates
niloticus L. in lakes Victoria, Kyoga and Nabugabo before
and after its establishment were examined and compared with
the situation in Lake Albert and other habitats where the
predator is native.
habitats initially decreased from a level that was similar
to that in Lake Albert to one that was significantly lower
and then persisted when species that are apparently
resilient to Nile perch predation remained. Afterwards,
stocks of some species began to recover. The types of prey
eaten in the from predominance of
haplochromines to types, sizes and numbers similar to those
eaten in Lake Albert and other native habitats. The
condition factor of the Nile perch which was initially
higher in the new habitats decreased and remained at values
which although lower than in Lake Albert, are not below the
lowest values recorded in a native habitat. Growth rates of
juvenile Nile perch were within the ranges reported in
native habitats. The size at first maturity shifted from
smaller to larger sizes, which are similar to those in lake
Albert; this increases overall reproductive potential
because fecundity is proportional to the cube of the length.
Only the proportion of females in invaded lakes decreased to
significantly lower values than in but the
reason for this is obscure. Since all but one
new habitats changed
Lake Albert
of the
Fish species diversity in the new the situation where Nile perch has remained in balance with
its prey community for
lakes recently invaded by Nile perch
sustain production.
variables examined have converged on values indicative of
a long time, the fisheries of the
can stabilize and