Embryonic developmental stages, different doses of inducing hormones and effect of different larval feeds on growth and survival of spiny eel, Macrognathus aculeatus (Bloch, 1786) larvae

Abstract

Induced breeding of Macrognathus aculeatus was carried out in order to determine the most appropriate dose of carp pituitary extract (CPE) and OVAFISH hormone. The best dose of CPE was 100 mg/kg body weight of female and 45mg/kg body weight of male with fertilization rate 81.34% and the best dose of OVAFISH was 1.5 ml/kg body weight of female and 0.75 ml/kg body weight of male with fertilization rate 91.96%. The fertilized eggs were round, sticky, demersal in nature and greenish in color. The perivitelline space of fertilized eggs was observed in 17 min. The First cleavage appeared at 56 min after fertilization (AF), producing two equal blastomeres. The cell division was completed in 4.17h. The fertilized egg took 6.47, 10.54, and 15.12 h to reach morula, blastula, and gastrula stage respectively. The eggs were hatched 34.17h AF at 27-28°C. Five days old post-hatchlings were reared for four weeks in a 160 L tanks using four different diets i.e., artificial feed, mix zooplankton, artemia nauplii and egg custard. The finding showed that hatchlings fed on mix zooplankton had a higher specific growth rate (SGR) (9.60±0.25). The significantly higher mean survival rate was also observed in larvae fed with mix zooplankton (47.67±11.25%) followed by artemia nauplii (38.5±5.4%) and artificial powdered feed (18.17±3.68%) for 28 days experiment. Our finding suggests CPE best dose @ 100mg/kg body weight for female and 45 mg/kg body weight for male and best dose of OVAFISH @1.5 ml/kg body weight of female and 0.75 ml/kg body weight of male for induced breeding. While in larval rearing experiment highest survival and growth rate was obtained in the larvae fed with mix zooplankton for 28 days trial.