BackgroundThe mandarin fish (Siniperca chuatsi) is an important and widely cultured fish in China. However, the lack of selective breeding of mandarin fish in previous decades has resulted in a decline in the growth rate of pond-cultured fish, a shortened period of sexual maturity, and reduced disease resistance; these issues seriously affect the quality and safety of the fish products. Therefore, it is necessary to establish a selective breeding program for the mandarin fish to improve the economical traits of the fish and to sustain the development of the mandarin fish industry.ResultsWe constructed a high-density linkage map for it based on double digest restriction site associated DNA sequencing (ddRAD-Sequencing). This map contained 3283 dimorphic single nucleotide polymorphism markers and 24 linkage groups (LGs). The total map-length was 1972.01 cM, with an average interlocus distance of 0.61 cM. One significant quantitative trait locus (QTL) for sex determination trait was detected on LG23, which was supported by five markers, clustered between 60.27 and 68.71 cM. The highest logarithm of odds value (17.73) was located at 60.27 cM, near the marker r1_73194, accounting for 53.3% of the phenotypic variance. Genotypes of all the male fish on r1_33008 were homozygous, whereas those of all females were heterozygous. Thus, LG23 was considered a sex-related linkage group. Eleven significant QTLs, for three growth traits, at two growth stages and the increased values were distributed on four LGs; their contributions to the phenotypic variation were quite low (12.4–17.2%), suggesting that multiple genes affected the growth traits.ConclusionThis high-resolution genetic map provides a valuable resource for fine-mapping of important traits and for identification of sex-related markers that should facilitate breeding of all-female mandarin fish for aquaculture and mechanistic studies on sex determination.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3830-3) contains supplementary material, which is available to authorized users.
The conventional controller for output tracking of a class of nonlinear system is not valid when encountering the singularity (i.e., division-by-zero) problem. To conquer the singularity problem, Zhang et al. have proposed a simple yet effective controller design method, i.e., aiding the conventional controller with gradient dynamics (GD), yielding a z0g1 controller in the framework of Zhang-gradient (ZG) method. As an indepth research, this paper provides the theory and proof on the performance of this z0g1 controller, which is exploited to conquer the singularity problem while fulfilling the trackingcontrol task. Besides, simulations and experiments substantiate and complement the theoretical analyses of such a z0g1 controller.
SummaryLength-weight relationships were determined for three fish species [Bregmaceros rarisquamosus Munro, 1950; Sardinella albella (Valenciennes, 1847)
| INTRODUCTIONThe South China Sea has high marine fish species richness and endemism (Xiong et al., 2017). However, the information of Chinese marine fish is very scarce. Length-weight relationship (LWR) is a widely used tool in fisheries science and management (Xiong et al., 2015). In this study, the LWR for Bregmaceros rarisquamosus Munro, 1950, Sardinella albella (Valenciennes, 1847, and Cynoglossus macrolepidotus (Bleeker, 1851) were first determined. W is the weight (g) and L is the length (cm), was fitted with a simple linear regression model using log-transformed data. The 95% confidence interval (CI) was determined for parameters a and b (Froese, 2006).
| MATERIALS AND METHODS
| RESULTSAll sample size, size range, length-weight parameters a and b, and the correlation coefficient (r 2 ) are listed in Table 1.
| DISCUSSIONThe estimated values for the parameter b remained for all three studied species within the expected range of 2.5-3.5 (Froese, 2006
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