Embryonic Development, Larval Rearing, and Digestive Tract and Enzyme Ontogeny of Hilsa Shad, Tenualosa ilisha

Abstract

Production of fish larvae in captivity and its rearing are the key factors behind the successful mass propagation of any commercial important aquaculture species. Towards this goal, efforts were carried out to standardize fry production and larval rearing of hilsa shad, Tenualosha ilisha. Artificial fertilization of hilsa was done through dry stripping method. Experiments were carried out to understand the embryonic development, larval rearing, ontogenic development of gut and digestive enzymes. Significantly (P <0.01) higher (86.33±0.88%) fertilization and hatching rate (57±0.58%) was recorded when hydration and incubation were done using river water (salinity 0.19 ppt, hardness 950-980 ppm). After an incubation period of 22-24 h at 23±1.0oC temperature, larvae hatched out. Newly hatched larvae measured 2.20±0.23 mm in total length with large yolk sac and 4 to 6 small oil globules. On the 5th day after hatching, the alimentary canal was noticed and the mouth opened between 3 rd and 8 th days. The aperture of mouth was found to be 82 µm. Larval rearing at different salinity for 15 days revealed the highest survival (53.67±3.75%) when reared at 1.5 ppt. Presence of digestive enzyme (amylase, acidic protease activity, alkaline protease, and lipase) was first detected on 5th - day post-hatching. Fourteen days old larvae were characterized by the absence of oil globule and a well-developed intestine with food particle in the gut. Considering the mouth opening and presence of digestive enzymes on 3rd day and 5th respectively exogenous feeding of suitable particle size may be introduced from 3rd day of hatching onwards.