Population Surveillance of Poecilia reticulata in Kolkata, India: Implications in Mosquito Regulation
Background: The guppy, Poecilia reticulata (Cyprinodontiformes: Poeciliidae) is promoted as a biological control agent of mosquitoes. Augmentative release of guppy has led to the elimination of the mosquitoes at a local scale, though resurgence is possible in absence of adequate population of guppy in the larval habitats. Surveillance of the guppy population in the introduced habitats is therefore required to support the use and enhance the success of biological control.
Objective: Monitoring of the guppy population in the sewage drain larval habitats where P. reticulata have been released to justify the colonization and establishment in the habitat. Assessment of the aquatic community that can sustain the population in absence of the target prey will substantiate the vector management strategy employing guppy as a bio control agent.
Method: Random sampling of guppy with associated local fauna during every season from different sampling sites of Kolkata and adjoining areas in consecutive three years was carried out. The population of guppy was categorized in terms of the size groups and temperature regimen. Analysis of the relative density of mosquito and guppy was made to highlight the effects of guppy in the sewage drains.
Results: The population of guppy varied significantly with reference to the samples and the size classes constituting the population. Variations in the population size classes corresponded significantly to the ambient water temperature explaining ~70% variation of the data observed on the population abundance of guppy. Significant differences in the composition of the macro invertebrates (prospective prey) and the guppy population was observed, that could be represented through a Principal component analysis which explained for more than 60% variations of the data obtained on the relative abundance of the representative members of the aquatic community. A negative correlation was observed for the relative abundance of mosquito immature and guppy in situations where both the groups were present. Overall, the relative abundance suggested the colonization and establishment of the guppy and the local elimination of the mosquito immature in the sewage drains sampled.
Inference: From the results it is apparent that the guppy population colonized and established in the sewage drain habitats following the augmentative release to regulate mosquito. The heterogeneity in the size class of guppy population was evident in the sewage drain habitats. Alternative prey population in the sewage drain ensures the sustenance of the guppy in the long run. A negative correlation between mosquito immature and the guppy suggests that the availability of the guppy in the habitats reduces availability of mosquito both as a direct predatory impact as well as indirect effect on the oviposition. The observations indicate that guppy can colonize and sustain in the sewage drain habitats for long time period and reduce the possible colonization of the mosquito in the sewage drain habitats.