Study On Biology Of Gadus Macrocephalus Tilesius During Early Developmental Stage

In this dissertation, the biology of Gadus macrocephalus during earlydevelopmental stage were focused, the mainly areas are follows: study on earlydevelopment of G. macrocephalus; effects of starvation on growth, morphology andbehavior; effects of light on feeding.The major obtained results were as follows:The morphological characteristics of early development of G. macrocephaluswere described during February and April2011in Key Laboratory of NorthMariculture, Ministry of Agriculture. The post embryonic development of G.macrocephalus was divided into yolk-sac larva and late-stage larva, based on theyolk-sac exist or disappear. The average total length of newly hatched larva was3.80±0.18mm. At the water temperature of7.8～10.0℃and the salinity of30, theembryonic development took9days to develop into yolk-sac larva, and then tookanother55days to develop into late-stage larva. The mouth could be seen eight daysafter hatching.64days post hatch, the larval already has three dorsal fin and twoanal fins, keeping begun to take shape, but fin membrane has not completelydisappeared.The effects of starvation on growth, morphology and behavior were researchedabout the experimental animal, G. macrocephalus larvae in February2011. Theresults showed that under the water temperature of10.0～11.0℃, the initial feedingtime of the starvation group and the feeding group were at5d,when the volume ofyolk sac was0.0062mm~3which was smaller than the volume of yolk sac was0.2402mm~3at the beginning of incubation. After8DAH, the total length, eyediameter, body length and length before anus of G. macrocephalus had significantdifference between the starvation group and the feeding group(P<0.01).A similarsituation appeared in inflation rate of swim bladder and the volume of swim bladder.The initial feeding rate was30%, which reached90%at7d.The point of no return(PNR) was in9d.At10d, the larvae of the starvation group died completely. Thestage of mixotrophism was short, only2～3dates. Therefore, the experimentproved that resistance to hunger ability of G. macrocephalus was poor.The effects of light on the feeding of larval G. macrocephalus were studied.Experiments consisted of natural light group and continuous light group. Anapparent feeding peak appeared at12:00AM in the both group. In the continuous light group, the feeding rate was higher than that of natural light group in the night.And daily feeding amount was109.9%of that natural light group. The feedingrhythm of larval G. macrocephalus has a rule. During0～1000lx, the feedingintensity was relatively high under300and700lx and500lx is the optimumillumination for the larvae to feed. The feeding rate reaches the max in10minuteunder500lx, decreased with the feeding time. It is not conducive to the growth anddevelopment of the larvae under too strong or too weak illumination.