STUDIES ON THE DEVELOPMENT OF EMBRYO AND LARVA OF NORTHEN PIKE (ESCOX LUCIUS LINNAEUS)

The eggs of Escox lucius are sticky and spherical shape in golden yellow color. The diameter of the egg was from 1.9 to 2.2mm. Under the water temperature ranging from 5.0 to 11.0℃,it took 185 hours and 18 minutes from fertilization to hatching with the total cumulative temperature of 2641.37℃. The embryonic development process could be divided into 6 stages, including fertilized egg stage, cell division stage, blastula stage, gastrula stage, neurula stage and organ formation stage, and contained thirty-three developing phrases as other teleost. The organ formation stage was longest during total embryonic development stage. It took 120 hours and 52minutes with total cumulative temperature of 1704 78℃, accounting for 64.54% of total cumulative temperature. Unlike common carp and silver carp, the heart formation phrase, heart beating phrase and olfactory socket phrase appeared earlier than muscle functionphrase. The newly hatched larvae lied on the water bottom with a big spherical yolk sac and without pigment on the body and their total length was 7.0 to 7.7mm. It took twenty-one days from hatching-out to all fins formation under the water temperature ranging between 12.0℃ and 22.0℃. At the age of 1 day, it appeared pigment on the head, the belly and the yolk sac. The gill arch appeared, and the pectoral fin appeared, and the end of the operculum started to dissociate, and the lower jaw bone formed and gill rake appeared and mouth opened at the age of 2,3,4and 5days, respectively. At the age of 6 and 7 days, the kiss appeared and the operculum opened. The mouth formed and swimming bladder formed and aired and started to swim up, and the enteron started to form at the age of 8 and 9 days, respectively. At the age of 11 days, the dorsal fin and anal fin appeared, and tail fin started to form, and the pleat of pelvic fin did not disappeared and the yelk disappeared. The total length of larvae reached 15 to 17mm and began to preyed on rotifer and small cladocerans mainly and started to attack other fishes at the age of 12 days. it began to prey mainly on big cladocerans and coppoda, and swallow fish once in a while after the total length of larvae reached 18 to 20mm. The feeding habit started to change at the age of 15 days and the teeth appeared at the age of 19 days. The total length of larvae reached 25 to 27 mm and all fins were the same as adult fish. The change of feed habit achieved. The fry could prey on small fish in the total length of 7 to 10 mm.