| Juvenile Pelteobagrus fulvidraco from the same brood were evaluated the effects of delayed initial feeding,size-growth dimorphism and feeding level on growth,the coefficient of variation,total weight and sexual grading.Effects of delayed initial feeding on survival,feeding and growth of Pelteobagrus fulvidraco larvae were investigated in the experiment.During the feeding level experimental,fish were divided into four groups and fed four levels:5%,3.75%,2.5%and 1.5%of the fish biomass in 12 experimental cages with three replicates for each treatment in a 70-day trial.During the size-grading experimental,fish were graded into large-sized grading group[(5.63±0.4) cm and(1.88±0.5) g,group B],small group[(4.85±0.2) cm and (1.11±0.2) cm,group C]and ungraded group[(5.32±0.5) cm and(1.60±0.5) g,group A]as control.Growth performances of Pelteobagrus fulvidraco of all the treatments were tested in 9 experimental cages with three replicates for each treatment in a 60-day trial.Growth,total length,total weight was checked every 10 days by checked same sample fish.At the end of the experiment,fish were killed and sexed.1.Larvae firstly fed 3 days post-hatch,arrived the point of no return(PNR) at 11 days exhaustion.The initial feeding rate was lower,then rapidly increased to the peak, lasted 6 days,after that,it progressively decreased.The highest initial feeding rate was 100%.The survival were not affected when the initial feeding was at the age of 2 days,and then,decreased with increasing of delayed feeding time.Growth rates were no affected when the initial feeding was at the age of 4 days,and then,decreased with increasing of delayed feeding time.The optimum first feeding time of Pelteobagrus fulvidraco larvae was 3-5 days after hatching.2.With the declining of feeding rate,GLW,GBW,SGR declined gradually.5%,3.75%groups markedly higher 2.5%,1.5%groups,but no significantly different among 5%and 3.75%(P＞0.05).With the declining of feeding rate,Feed efficiency increased gradually.2.5%,1.5%groups markedly higher 5%groups.There were no significantly between 3.75%and the other groups.The coefficient of variation increased fist and then decreased.Except in 2.5%group,male were growth significantly faster than female in each group.These suggest that feeding management could be used to regulate heterogeneity in Pelteobagrus fulvidraco culture.In terms of maximum body weight increase rate and maximum feed efficiency,the suitable feeding rate was the 3.75%of fish body weight.3.Growth rate of body length were size-dependent,large-sized group grew faster than small-sized group,but the difference between ungraded group and graded groups was not significant.The coefficient of variations of length and weight of ungraded group were higher than those of graded groups significantly,but the difference was not significant between group ungraded groups.Changing rate of coefficient of variation of length and weight of group small groups were higher than those of graded group and large-sized groups significantly,but the difference was not significant between graded group and large-sized groups.Size grading did not lead to improve growth rate of body weight,survival,specific growth rate of Pelteobagrus fulvidraco. The growth rate of body length and weight,specific growth rate of male were larger than female in all the groups,except growth rate of body length in graded group.The results suggested that size grading in early stage seems to be an unnecessary operation in cultivation of Pelteobagrus fulvidraco.
|
PDF Full Text Request