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.