马口鱼仔稚鱼发育观察及饥饿不可逆点的确定

Observation of early development and determination of the point of no return(PNR)in Chinese hook snout carp(Opsariichthys bidens)

为研究马口鱼(Opsariichthys bidens)早期生活史发育特点并确定其饥饿不可逆点(point of no return,PNR),在水温20.5~26.0℃条件下,研究了马口鱼早期发育的形态特征及饥饿对马口鱼仔鱼生长、形态和行为的影响。结果表明:马口鱼孵化后10日龄开口摄食,混合营养期为10~11日龄,12日龄卵黄囊完全消失,27日龄第一鳞片出现,43日龄鳞被覆盖完全;依据卵黄囊消失和鳞片形成的特点可将马口鱼仔稚鱼划分为早期仔鱼(0~11日龄)、晚期仔鱼(12~26日龄)和稚鱼期(27~43日龄);饥饿再投喂及不可逆点试验显示,在水温为(21.5±1.0)℃条件下,马口鱼的PNR为12~13日龄,14日龄饥饿仔鱼全部死亡。研究表明,马口鱼属于卵黄囊晚消失鱼类,该发育特征有助于其更好地适应野外生态环境,马口鱼仔鱼的混合营养期较短(仅为2 d),需适时下塘,从而提高仔鱼成活率。

In order to probe into the developmental characteristics of early development and to determine the point of no return(PNR)in Chinese hook snout carp(Opsariichthys bidens),the morphological characteristics of early development and the effects of starvation on the growth,morphology and behavior were investigated in Chinese hook snout carp larvae from 1 day post hatching(dph)to 43 dph juveniles at water temperature from 20.5℃to 26.0℃.The newly hatched larvae derived from artificial breeding were reared indoor and 9 dph postlarvae were reared and fed zooplankton in a 0.67 hm^(2) pond to observe the developmental characteristics and to determine the PNR.The results showed that 10 days old Chinese hook snout carp had initial feeding,with the mixed nutrition from 10 to 11 days old,completely exhausted yolk sac at 12 days old,and the first scales at 27 days old,fully covered scales at 43 days old.Thus,the Chinese hook snout carp larvae were divided into early fry(from 0 day old to 11 days old),late fry(from 12 to 26 days old),and juvenile stages(27 to 43 days old).The starvation and re-feeding test revealed that Chinese hook snout carp larvae had PNR at 12 days to 13 days old,and all died at 14 days old under starvation stress at water temperature of(21.5±1.0)℃.The finding indicated that Chinese hook snout carp as a fish species with late exhaustion of yolk sac was benifit to better adapt to the ecological environment in the wild,and that Chinese hook snout carp had only 2 d mixed nutrient period,and needed to be stocked into the pond at the right time,so as to improve the survival rate of the fry.