Abstract:
Biological control of Aedes mosquitoes has gained a wide attention as a successful vector control method for dengue. The present study investigated the predatory potency of selected freshwater fish species over Ae. aegypti larvae, in laboratory conditions. Adult fish specimens collected from aquaria or the wild were acclimatized in tanks with dimension of 60 × 30 × 35
cm, while colonies of Ae. aegypti were maintained under insectary conditions to supply fourth
instar larvae for the experiments. Individuals of six fish species (two being introduced and four
being native and endemic to Sri Lanka) were introduced into separate tanks with a density of
200 Ae. aegypti larvae in 1L of de-chlorinated water as the predation trials, with supplemental mosquito larvae when necessary. Prey mortality was recorded at six hour intervals for a
period of 48 hours. Each experiment was replicated five times. The predatory efficiencies of
six fish species denoted significant variations (p < 0.05), when evaluated using the General
Linear Model. The highest predation efficiency per unit mass was shown by Puntius bimaculatus (59.77 ± 5.48) followed by Poecilia reticulata (52.47 ± 5.12), Xiphophorus hellerii (48.15
± 2.76), Apolochilus dayi (43.57 ± 6.19), Rasbora naggsi (40.67 ± 13.05) and Belontia signata (24.93 ± 2.94), revealing both the native species Pu. bimaculatus and Ap. dayi as good
candidates for biological control of Ae. aegypti compared to introduced Po. reticulata and X.
hellerii. ANOSIM and cluster analysis suggested associations (in terms of their predation over
Ae. aegypti) among B. signata - Ap. dayi (exotics) and Po. reticulata - X. hellerii - R. naggsi
(predominantly exotics), leaving Pu. bimaculatus alone, indicating the latter to be unparalleled
as a mosquito bio-control agent. While further investigations are suggested, present preliminary
findings are important in the light of Po. reticulata been identified as an invasive species that
threatens the freshwater biota in Sri Lanka, after its introduction for mosquito bio-control.
