Current and potential distribution of the invasive apple snail, Pomacea canaliculata in Eastern Africa: Evidence from delimiting surveys and modelling studies.

Abstract

Pomacea canaliculata, commonly known as Golden Apple Snail (GAS), an invasive snail, has successfully invaded ecosystems outside its native ranges with negative impacts being reported. GAS was reported in Kenya in 2020 invading one of the largest rice-producing schemes, the Mwea irrigation scheme. Delimiting surveys were conducted in five major rice production schemes in Kenya to establish the boundary of spread since its first report and to help in the management and development of quarantine strategies to limit the spread of this pest within the scheme and other risk areas. In addition, an Ensemble model approach was used to model the potential distribution of GAS in Eastern Africa. Over 80% of the Mwea scheme’s sections were infested with GAS along the river and irrigation channel gradient from the initial infestation point (Ndekia). The mean adult/m2 and egg clutches count was 8.4 and 7.7, respectively. Significant difference was observed in number of adults/m2 and egg masses among the sections; X2(7) = 138.69, p< 0.001and X 2(7) = 114.17, p < 0.001, respectively. The survey did not find any adults or eggs of GAS in the Ahero, Bura, Hola and West Kano rice schemes. Most of the areas in Kenya were suitable for GAS invasion, though with significant variations across the country. At a regional level, the countries with the highest suitability for GAS were Malawi, Madagascar and Uganda. Mozambique, Tanzania and Ethiopia also had areas of high suitability, but these were more concentrated in specific areas in each of the countries. In comparison, suitability across Sudan and Somalia was very low. Strict quarantine measures should be instituted and implemented to curb not just the spread of GAS in Kenya but entry into uninvaded regions.