i.e. snail density in ponds stocked with
100–200 fry m−3 (n = 24) was 0.76 of that in ponds stocked with
less than 100 fry m−3 (p N 0.05), while the density in ponds stocked
with more than 200 was 0.15 (p b 0.01) of that in ponds stocked with
less than 100 fry m−3 (Table 2). Stocking density by pond surface area
showed the same trend but this was not significant. Host snail density
was not significantly associatedwith any other pond characteristics. Entering
both pond depth and stocking density as predictors of host snail
density made both predictors not significant. This is due to collinearity
between the two variables, i.e. farmers tend to stock by surface
area rather than by pond volume. Average pond depth for ponds
stocked with less than 100 fry m−3 was 1.09 m (range 0.8–1.3 m),
Table 1
Number of ponds (n=60) from where different snail families were collected, total number