Received: 19-10-2019 / Accepted: 19-01-2020
Morphological relationshipsbetween clutch and fecundity of black apple snail (Pila polita) was studied on the 349 clutches (in Dong Thap, Hau Giang and Vinh Long provinces) with the number of: 121, 113 and 115 clutches, respectively, which were collected from May to August 2017.At the same time, four-repeated experiments on rearing of 3 height groups snails (48.0-50.0 mm; 52.0-54.0 mm and 56.0-58.0 mm) were done to determine fecundity. The rearing was carried out in foam containers (60 × 45 × 40 cm) with a density of1 pair of broodstock snail/tank. Results of the study showed that the morphological relationship between clutch weight with clutch dimensions, the length of the clutch with the size criteria is quite tight (R2= 0.6-0.8). The fecundity of black apple snail is 208 eggs/snail, relative fecundity is 6208 eggs/kg snails. Spawning activity of black apple snail is mainly at night, starting from 20 pm to 4 am and lasts up to 8-12 hours. Black apple snail female is able to re-reproduce for the first time (42.7%).However, the ratio of the second batch is very low (8.3%), the average time for re-spawning of black apple snail is 42.2 days.
