| Gobiocypris rarus is a rare and endemic fish in China,with short breeding period,and they are sensitive to water environment changes extremely.Gobiocypris rarusis recommended to China’s chemical management experimental animal.Bait has important effects on fish’s growth and reproduction,but so far there has few reports about Gobiocypris rarus standardized system.So this study focused on the period of larvae digestive tract and the digestive enzyme vigor and development degree,aimed at explain more about the relationship between the bait and digestive tract development,and then find the most suitable fish bait on the stage of larvae.Based on the result,the optimal feeding strategy of juvenile fish stage,adult fish stage even sexual maturity was further explored.This study was provided experimental basis and supplementary basic theoretical data for Gobiocypris rarus’ s standardized breeding.In order to find proper bait for the larvae and juvenile Gobiocypris rarus,we divided newly hatched larvae into three groups randomly: live bait group,artificial diet group and mixed group.Each group has three parallel samples.The fish of each group were fed since 3 dah(day after hatching)with the three different diets mentioned before,and the growth and survival rates of the larvae and juveniles were measured on 10,15,20,25,30,35 dah.We also studied the structure and the function of the digestive tract by histological methods,and measured the digestive enzyme activities on 35 dah.Results showed that:(1)the live bait group had the highest survival rate on 35 dah;(2)from 15 dah,fish in the live bait group showed the best growing performance,and kept that trend until 35 dah;(3)muscle layer thickness and mucous cell numbers of the entire digestive tract in the live bait group were the highest,which suggested a more developed digestive tract and thus a better capacity in digestion and absorption;(4)themaximum activity of trypsase was observed in the larvae and juvenile group fed with baits.All those results mentioned above indicated that: compared with artificial diet and mixed,live baits were the best choice for the growth and development of larvae and juvenile Gobiocypris rarus.We suggested that live baits should be taken to feed larvae and juvenile Gobiocypris rarus in the process of standardized cultivation.In order to find a proper bait of larva and adult fish Gobiocypris rarus,we divided hatched for five weeks(35 day after hatching)fishes into five groups randomly: A group was fed with Artemia nauplii;Group B,Artemia nauplii was fed for 6 days,1day was fed with commercial micro pellet diet of each week;the C group was fed Artemia nauplii for half weeks,and the another half weeks was fed artificial diet;the D group was fed Artemia nauplii for 1 day per week,and 6 day sartificial dietper week;the E group was fed the artificial diet.Each group was fed with a feeding satiation strategy.Each 2 weeks counted growth and survival indicators until twenty-first weeks(147 dah).Reproductive capacity and offspring abnormal rate were calculated after spawning.The gonads obtained in 17weeks(119 dah)were used for histological studies.The results showed that:(1)E group survival rate and specific growth rate was significantly lower than other groups(P<0.05);(2)reproductive capacity of B group was significantly higher than other groups(P<0.05);(3)different feeding strategieshad no significant effect on testis maturity,but had some effects on ovarian maturation.The results of this study suggest that the addition of Artemia nauplii better than single feeding with commercial micro pellet diet,which was more conducive to the growth and reproduction of Gobiocypris rarus.We suggestthat on standardized breeding process,larval and adult stage of the Gobiocypris rarus take Artemia and the feed ratio is 6:1 the best way.We suggested that the feeding ratio of Artemia nauplii and commercial micro pellet diet is 6:1 are the better ways for larvae and juvenile Gobiocypris rarus in the process of standardized cultivation. |
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