ẢNH HƯỞNG CỦA VIỆC THAY ĐỔI CHIỀU CAO CỘT NƯỚC VÀ THỜI GIAN THỰC HIỆN ĐẾN HIỆU QUẢ SINH SẢN CỦA ỐC BƯƠU ĐỒNG (Pila polita)

Abstract

This study aimed to evaluate the effects of different stimulation methods on spawning of the black apple snails, Pila polita. The experiment was conducted in 1 m³ tanks (1×1×1 m) a density of 15 pairs of broodstock snail/tank where the height of water column initially was 40 cm, including six treatments with 6 different water exchanging regimes: 1) Adding 50% water+2 hours drying in the shade (A50-2h); 2) Adding 50% water+3 hours drying in the shade (A50-3h); 3) Adding 50% water+4 hours drying in the shade (A50-4h); 4) Discard 75% water+2 hours drying in the shade (D75-2h); 5) Discard 75% water+3 hours drying in the shade (D75-3h) and 6) Discard 75% water+4 hours drying in the shade (D75-4h). Each treatment was replicated 3 times. Black apple snails were dried in the shade according to the time corresponding to each treatment. Results showed that the highest spawning rate occurred at A50-2h and D75-2h (74.4-77.2%) were higher and significantly different (p<0.05) as compared to A50-4h and D75-4h (58.9-62.8%). The broodstock snails in treatment A50-3h released highest egg clutches and reproductive efficiency (11.8 clutch/m²; 3.92 clutch/day/m²) and statistically different from A50-4h or D75-4h (p <0.05). The quality of snail eggs and new hatching snails were not affected by the different reproductive stimulation methods.