Table 1 Snail fauna and distribution in small water canals, rice fields and fish ponds each represented by 30 sites located in two communes, Nhgia Lac and Nhgia Phu, in Nam Dinh province, northern Vietnam
|  | Small canals (n = 30) | Rice fields (n = 30) | Fish ponds (n = 30) | ||||||
|---|---|---|---|---|---|---|---|---|---|
Snail species | No. of sites | No. of snails | % | No. of sites | No. of snails | % | No. of sites | No. of snails | % |
Thiaridae | Â | Â | Â | Â | Â | Â | Â | Â | Â |
  Thiara scabra | 6 | 1641 | 19.1 | 0 | 0 | 0.0 | 13 | 1214 | 10.4 |
  Tarebia granifera | 0 | 0 | 0.0 | 0 | 0 | 0.0 | 3 | 601 | 5.2 |
  Melanoides tuberculata | 13 | 2697 | 31.3 | 10 | 480 | 10.1 | 27 | 4637 | 39.9 |
  Sermyla riquetii | 2 | 346 | 4.0 | 1 | 465 | 9.7 | 5 | 1892 | 16.3 |
Bithynidae | Â | Â | Â | Â | Â | Â | Â | Â | Â |
  Bithynia fuchsiana | 5 | 167 | 1.9 | 17 | 984 | 20.6 | 5 | 23 | 0.2 |
Stenothyridae | Â | Â | Â | Â | Â | Â | Â | Â | Â |
  Stenothyra messageri | 11 | 1342 | 15.6 | 7 | 236 | 4.9 | 1 | 5 | 0.0 |
Other | Â | Â | Â | Â | Â | Â | Â | Â | Â |
  Neritina violacea | 1 | 6 | 0.1 | 0 | 0 | 0.0 | 1 | 1 | 0.0 |
  Angulyagra polyzonata | 15 | 927 | 10.8 | 4 | 33 | 0.7 | 29 | 3202 | 27.5 |
  Idiopoma umbilicata | 1 | 6 | 0.1 | 1 | 4 | 0.1 | 0 | 0 | 0.0 |
  Pila polita | 0 | 0 | 0.0 | 0 | 0 | 0.0 | 2 | 2 | 0.0 |
  Pomacea canaliculata | 8 | 48 | 0.6 | 2 | 2 | 0.1 | 5 | 16 | 0.1 |
  Pomacea insularum | 9 | 125 | 1.5 | 9 | 200 | 4.2 | 7 | 13 | 0.1 |
  Polypylis hemisphaerula | 8 | 400 | 4.6 | 6 | 26 | 0.5 | 1 | 16 | 0.1 |
  Gyraulus convexiusculus | 12 | 864 | 10.0 | 14 | 461 | 9.7 | 1 | 5 | 0.0 |
  Lymnaea spp.a | 4 | 34 | 0.4 | 9 | 1878 | 39.3 | 4 | 6 | 0.1 |