Artificial fertilization, embryonic and larval development of Hilsa, Tenualosa ilisha (Hamilton)

Abstract

Hilsa, Tenualosa ilisha is an important commercial fish of the Indo-Pacific region, especially in Bangladesh, India and Myanmar. Recently, catch of this species has declined due to overfishing and various ecological changes. In the present study, at first the embryonic and larval development of T. ilisha was studied in detail over 15 days. This was followed by examining the effects of different water sources on breeding performance. To obtain the gametes, migratory oozing male and female collected, bred through dry stripping (n=3) and fertilized eggs were oxygen packed and transported to laboratory. The photomicrographs of all developmental stages of live embryo and larvae during incubation and after hatching were documented with the aid of a light microscope. Results demonstrated that morula, blastula, gastrula, neurula, somatogenesis and hatching began at 1:00, 3:30, 7:30, 11:30, 12:30 and 21:00 h post stripping (hps), respectively at 26 ± 0.91 °C water temperature. Heartbeat and muscular contraction of embryo commenced at 11:30 and 18:00 hps, respectively. The newly hatched larvae measured 2.50 ± 0.16mm in total length with a yolk volume of 0.416 ± 0.157mm3. Key characters such as appearance of pectoral fin, opening of mouth, development of digestive system and anal pore of larvae were noticed on 2, 3, 5 and 8 dph, respectively. Yolk sac and oil globule were completely exhausted on 4th and 15th days post hatching (dph), respectively. Ten days old larvae commenced exogenous feeding. Breeding performance in three different sources of fresh-water, such as river water (RW), potable drinking water (PW) and freshwater from deep bore well (BW) was evaluated. Result of this study showed that the fertilization (34 ± 5.5%) and hatching rate (5 ± 1.5%) were significantly (P < .05) low in PW compared to RW and BW, due to low hardness and poor Ca+2 and Mg+2 ion concentration. Results of second experiment indicate that either filtered RW or BW is ideal for hilsa breeding. The present study will have substantial impact on developmentof aquaculture and conservation of hilsa.