Fry Rearing Of Burbot And Effects Of Temperature On Growth And Food Consumption Of Juvenile Burbot

Burbot,Lota lota is the only species of freshwater fish among the family Gadidae. Because of its delicious meat, abundant nutrition and bigger liver,it has high edible and economic value.In China,the distribution of this species is only limited in Erqisi River of Xinjiang Province,Heilongjiang and Yalujiang water systems.In recent years,the number of burbot decreases gradually with excess catching,therefore,it has been listed as rankⅡnational protected fish.It is urgently to protect burbot and exploit its breeding.Up to now, artificial breeding technology of burbot has not been reported,in the present study,the techniques of burbot larvae culture,especially the effect of temperature on the food intake of its juvenile period were explored.The main results are as follows:The early larvae (about 3㎜) are smaller than that of the other kinds of fish larvae. It has relative bigger yolk bag.Its floating period,especially flat swimming,lasted longer time,its livers and other organs developed slowly and the beginning time of eating is more later (12-15d).That may be related to the result of adapting to low water temperature for long time. The larval development of burbot was divided into five periods based on the morphology, structures,movement and types of food consumption at different developmental period.They are seeding floating,flat swimming,mouth opening,bait changing (seeding period)and juvenile fish.Early young fish adapted to a wide range of temperature change, which can survive from 0℃to 12℃and have low dissolving oxygen,even on the conditions of 3 mg/L.The early larval burbot is positive to faint light, but the juvenile fish becomes negative to light.Living habit changed from floating to flat swimming and then bottom dwelling with different growing period.Shelter is more necessary at late developmental period.Food intake is stimulated by vision in the baby period of burbot,the baby fish has special choice to the bait when began to eat;the best bait for larval burbot beginning to eat was rotifer in fresh water and the surviving rate reached 95.42%.Burbot has complex procedure of baiting transition,the type and size of baits changed with the changing of growth and living style.The bait selecting of juvenile is the precondition of burbot breeding industrialization. Bait domesticating for juvenile showed that burbot can feed on spray of carp fish,larvae of carp fish and also the fresh fish pieces.After shortdated domestication of artificial feed,about 40% juvenile can get food,which showed burbot has potential to eat artificial feed.The result of breeding at six temperature level(12℃,15℃,18℃,21℃,24℃,27℃) showed,the eating rate and SGR are highest,bait index is lowest at 15℃of water.The analysis of variance showed that there has significant effects on FR,FC,SGR of burbot in different temperature(F4, 10=20.448,p=0.00008;F4, 10=21.815,p=0.00006;F4, 10=33.688,p=0.00001),the result of growth increasing by food intake is:15℃﹥18℃﹥12℃﹥21℃﹥24℃.When at about 27℃,burbot hadn't eat any more,even to death.Result of analyzing the relations between temperature and I0,FC,FR,SGR,Rw,RL by the model of y=aT2+bT+c showed: I0=(-0.00267)T2+(0.08144)T+(-0.01379) (P<0.01,r=0.9635) FR=(-0.01853)T2+(0.577757)T+(2.47605) (P<0.01,r=0.9304) FC=(0.069365)T2+(-2.1071)T+(20.5636) ( P<0.01,r=0.9452) SGR=(-0.01194)T2+(0.361139)T+(-1.2584) (P<0.01,r=0.9396) RW =(-0.59948)T2+(18.1171)T+(-69.82) (P<0.01,r=0.9251) RL=(-0.13429)T2+(3.97881)T+(-15.993) (P<0.01,r=0.9726)According to y=aT2+bT+c to analyze the pertinence between SGR and temperature,the result showed the best suitable temperature of baby fish of burbot is 15.12℃.The result is basically consistent with the experimental data of feeding and growth.