Forty snails were randomly sampled for initial weight measurement. Weight measurement
was repeated on day 30, 60, 90, and 120 in order to determine growth rate of the snails.
Wet weight of all snails from each tank was measured individually to the nearest 0.01 g.
Mortality was determined by counting the number of dead snails and expressing the results
as a percentage of the number of snails at the start of the experiment. The following indices
of growth were calculated at the end of the experiment: Weight gain (WG) = final weight
(g) - initial weight (g); Percent weight gain (PWG, %) = [(final weight - intial weight)/
initial weight] 9 100; Specific growth rate (SGR) = 100 (ln Wf - ln Wi)/T; where
T = 180 days of culture; Feed conversion ratio (FCR) = feed intake (g)/weight gain (g)
and Survival rate (SR) = 100 9 (final snail number)/(initial snail number).