Analysis on the Effects of Morphological Traits of Lutraria sieboldii on Its Body Mass Trait

[Objectives]This study was conducted to explore the relationship between morphological traits and body mass trait of Lutraria sieboldii.[Methods]110 were randomly selected from 120 2^(nd)-instar L.sieboldii collected from the Tieshangang area of Beihai,Guangxi,and 132 were randomly selected from 150 shellfish at the instar of 0.6.Their morphological traits were measured:shell length(SL),shell height(SH),shell width(SW),anterior length(AL),posterior length(PL),nose length(NL)in closed shell state,and maximum open shell width(OS)between two shells in closed shell state,and the body mass trait BM was also measured.Statistical methods such as path analysis and multiple regression were used for data analysis,and the effects of these seven morphological traits on the body mass trait were studied,respectively.The correlation between the tested seven quantitative traits and one body mass trait was all positive,all reaching an extremely significant level(P<0.01).[Results]The body mass trait of the shellfish at the instar of 2 had the highest correlation coefficient with shell length(0.922),that is,shell length had the greatest direct impact on the body mass trait;the path coefficient was 0.700;and the final multiple regression equation established was BM=-124.882+1.189 SL+1.551 SH+1.035 SW+0.119 NL,and the total determination coefficient(R^(2))on body mass was 0.849.The body mass trait of the shellfish at the instar of 0.6 had the highest correlation coefficient with shell length(0.859),that is,shell length had the greatest direct impact on the body mass trait;the path coefficient was 0.494;and the final multiple regression equation established was BM=-1.917+0.111 SL+0.021 NL+0.078 SW+0.032 OS,and the total determination coefficient(R~2)on body mass was 0.828.The multivariate regression variance analysis showed that the regression between the morphological traits and body mass trait of the L.sieboldii at the instars of 2 and 0.6 reached an extremely significant level(P<0.01).[Conclusions]This study provides a scientific basis for the selection of broodstock in the selection and breeding of L.sieboldii.

Analysis of the Southern China Tilapia Production and Economic Benefits of Different Breeding Patterns in 2018

Cost-benefit analysis and breakeven point were used to analyze the production cost and economic benefit of tilapia pond monoculture and polyculture.From the aspects of tilapia production and economic benefit,this paper summarized the current production status and the characteristics of tilapia industry development and analyzed its developing trend.The results indicated that feed cost,pond rates and labor cost are the main production costs,and the production cost of polyculture is significantly lower than that of monoculture.Through comparative analysis,it is proposed that the tilapia industry should be reasonably guided to the intensive,standardized and pollution-free direction.Specifically,it is necessary to improve the coverage of improved varieties,strengthen disease prevention and control and promote the healthy farming model of tilapia.We also should strengthen the training of tilapia production techniques and the quality and safety testing of tilapia products,and accelerate the development of tilapia industrialization,so as to promote the sustainable and healthy development of tilapia industry.