PRELIMINARY STUDIES ON ARTIFICIAL PROPAGATION AND EMBRYONIC DEVELOPMENT OF MEGALOBRAMA PELLEGRINI

Megalobrama pellegrini, a cyprinid fish belonging to Cltrinae, lives mainly in the upper researches of the Yangtze River. This bream is a rare commercial fish in Sichuan Province because of the low abundance in natural environment. Due to the loss of habitat after the completion of the Three Gorges project, it was predicted that the population sizes might decrease. Taking suitable countermeasures including artificial breeding and stocking become very urgent for conservation and resource recovery of this endemic species. Habitat, biology, reproductive ecology, artificial breeding and stocking of M. pellegrini were stdudied since 2001. The present paper reports the results of artificial propagation and observation on embryonic development. The parent fish were collected in the Longxi River, one of the first-order tributary of the Yangtze River at Luzhou, Sichuan Province. The fertilization rate was only 12.0% when artificial fertilizations were done as soon as the parent fish were collected. A total number of 32 females and 33 males were injected with LRH-A, HCG, pituitary gland (PG), or a mixture of these three reagents, to induce spawning. All males released sperm and 20 injected females spawned. The average fertilization rate was 62.1%, while the average hatching rate was 44.7% in the 12 successful induced reproduction. According to the spawning, fertilization, and hatching rates, a mixture of 3 mg of pituitary and 3μg of LRH-A 2 per kg fish was suggested to be the appropriate dosage. The latency between the second injection and initial egg release varied from 6.5 to 12 hours when water temperature ranged from 21.0 to 27.0℃. The eggs were adhesive, spherical,with a diameter of 1.53-1.80mm, and the diameter of the yolk was about 1.17-1.45mm. Embryonic development could be divided in 18 stages, and the characteristics of each stage were described and illustrated in this paper. Ontogenesis process was influenced remarkably by water temperature. The incubation duration lasted about 68h50min, 55h10min, 42h50min and 31h40min under a water temperature of 19.5-21.0℃, 21.0-21.9℃, 22.5-23.8℃ and 26.0-28.8℃, respectively.