Ecological study of Anopheles sundaicus larvae in a coastal village of North Sumatra, Indonesia : II Environmental factors affecting larval density of An. sundaicus and other anopheline species

Abstract

The relationship between larval density of Anopheles sundaicus Edwards and several environmental factors was examined by 215 data which were obtained from April to June, 1982 in 38 ponds in a coastal village of North Sumatra, Indonesia. The data were analyzed by the quantification theory type I method. Density of the larvae was higher in the waters where fish were scarce, salinity was 0.5-0.8%, and/or the surface received much sunlight. Water salinity was most contributive to the density, followed by fish-abundance and sunlight condition. These three factors altogether contributed to 21% of total variance of the density. The contribution of fish-abundance suggested suppressive effect of predatory fish against the larvae in the field. Larval density of anopheline species other than An. sundaicus (mostly An. hyrcanus group) was much lower than that of An. sundaicus. When compared within other Anopheles group, the density was a little higher where water depth was greater (81-100cm), salinity was less than 0.4%, transparency was higher, and/or bloom of fibrous floating algae was luxuriant. Water depth was most contributive, followed by salinity, algal abundance and transparency. Contribution of these four factors altogether was 15% of total variance of the density.