Experiment And Genetic Parameter Analysis Of Tolerance To Ammonia Nitrogen Stress In Turbot(Scophthalmus Maximus L.)

Turbot(Scophthalmus maximus L.)is an important European valuable marine aquaculture species,because of its fast growth,strong resistance,high nutritional value,and quickly became one of the important mariculture species in northern China after the introduction in 1992,and create the flowing factory farming mode of “green house +deep well sea water”.However,the development of the aquaculture mode is gradually being restricted because it is conflicted with the requirements of the sustainable development of aquaculture ecology,and trying to translate to the closed recirculating aquaculture mode.At present,China's closed circulating water culture mode is still in the initial stage,and the water treatment technology is relatively backward,in the intensive farming process can easily lead to high water ammonia content,causing great impact on aquaculture production.There have problems such as serious degradation of germplasm,slow growth,weak disease resistance,high rate of albino turbot and many other issues because of the germplasm resources single,inbreeding,mismanagement and other reasons in our country.In order to ensure the sustainable development of turbot aquaculture industry,Our laboratory has been engaged in the turbot variety breeding for more than ten years,which has accumulated a large amount of scientific data,and has abundant experimental materials.This research studied the acute ammonia toxicity to turbot in the recirculating aquaculture conditions based on the previous work,and estimate the heritability and the correlation of ammonia resistant trait,body length and body weight use the animal models in 4month-old juvenile turbot,and compared the advantages and disadvantages of two methods of breeding value selection and phenotypic value selection in order to provide scientific guidance for the circulating water,and provide a theoretical basis for the breeding of Ammonia Resistant turbot.The specific results were as follows:1.According to the experiment of acute toxicity effect of ammonia nitrogen on turbot we get the results as follows: the median lethal concentration(LC50)of 24,48,72 and 96 h for un-ionized ammonia on 4 month-old turbot were 2.19,1.94,1.80 and 1.72mg/L respectively.The LC50 of 24,48,72 and 96 h for un-ionized ammonia on 8 month-old turbot were 3.64,3.02,2.93 and 2.86 mg/L respectively.The safe concentration of nonionic ammonia on 4 month-old and 8 month-old turbot were 0.17 and 0.29mg/L respectively.8 month-old turbot were more tolerant to ammonia nitrogen than the 4 month-old,and ammonia nitrogen acute toxicity comparison both on albino and normal and on female and male turbots revealed no significant difference based on this study.2.The concentration of 72 h LC50 of un-ionized ammonia to 4 month-old turbot was used to test ammonia resistant traits in 39 families with a total of 943 turbots,and estimated the genetic parameters for ammonia-resistant trait and growth traits.The results showed that the heritability of ammonia-resistant trait was 0.47 ± 0.19,belongs to higher heritability,reaching significant difference compared with 0(P<0.05).It has a potential of ammonia-resistant trait breeding based on phenotypic selection.Analysed the correlation between ammonia tolerance,body length and body weight of 4-month-old turbot showed that the genetic correlation between ammonia-resistant trait and body weight,ammonia-resistant trait and body length both showed a low linear positive correlation,which was 0.01 and 0.05,respectively.The phenotypic correlation between ammonia-resistant trait and body weight,ammonia-resistant trait and body length both showed a low linear negative correlation,which was-0.08 and-0.04,and the statistical test was not significant(P>0.05).These correlations were both very low,suggested that selection breeding aiming at ammonia-resistant trait will have no significant impact on body length and body weight.The selection efficiency was significantly higher than that of phenotypic value selection.This is the first study to compare the ammonia resistant ability of normal and albino turbot individuals,female and male individuals of turbot,and calculated the LC50 and safe concentration in different developmental stages of turbot.The research results provide scientific guidance for farming turbot in circulating water.At the same time,we first estimated the heritability of ammonia resistant trait and the correlation between ammonia resistant trait and growth trait in turbot,it has a certain reference significance for the next breeding of ammonia-resistant turbot.