1 Introduction

Chinese shrimp, Fenneropenaeus chinensis, is mainly distributed in Yellow Sea and Bohai Sea (Liu et al., 1959).As one of the most representative aquaculture species of China, F. chinensis has been one of the important commercial marine species in mariculture. Its aquaculture production accounted for 70% of the total shrimp production in China in 1990, reaching about 150000 metric tones (Liu, 2004). In 1993, a white spot syndrome virus(WSSV) epidemic broke out in shrimp aquaculture,which has severely decreased the shrimp production (Cai et al., 1995; Zhan et al., 1995). The annual yield of F.chinensis declined to less than 50000 metric tones today.Meanwhile, due to the lack of varieties, wild population of F. chinensis was often used to producing offspring.Such practice brought some problems to aquaculture; it uses populations without systemic selection, which are less adaptive, economic characteristics regressive and inbreeding. Such scenario severely restricted the sustainable development of F. chinensis aquaculture.

大肠埃希菌（Escherichia coli）、金黄色葡萄球菌（Staphylococcus aureus）、无乳链球菌（Streptococcus agalactiae）、停乳链球菌（Streptococcus dysgalactiae）是引发奶牛乳房炎的主要致病菌。大肠埃希菌、金黄色葡萄球菌由内蒙古农业大学兽医学院提供；无乳链球菌（CVCC3940）及停乳链球菌（CVCC3701）菌株从中国兽医微生物菌种保藏管理中心购买。

在我国，长期以来的应试教育造成了教师灌输知识、学生被动获取的单向学习模式，学生为了追求考试成绩，往往满足于对书本知识的记忆和模仿，而对于需要发挥主观能动性、同时又不属于考试必备技能的语言运用等技巧缺乏积极性。新课标背景下，高中教育对于学生学习的综合素质提出了新的要求，因此学生不仅要背诵词汇、语法，更需要加强对英语语言的综合运用，才能真正适应新教学的要求。语言的实用性学习，对于学生的积极性和自主能力要求较高，被动学习存在着明显的瓶颈。因此，高中英语学习的核心技巧，也是学习的基本要求，就是改变原有的教学模式，努力培养学生的独立自主学习能力，使独立学习成为学生的学习习惯。

从调查中可以看出，区域教研组内教师间的关系十分融洽，这种关系有助于教师形成归属感和认同感，而这种关系是建立在教研组“尊重、关爱、合作”的基本理念基础上的。

Selecting new varieties with the traits of fast growth and strong disease resistance is urgent, which is considered as one of the effective ways of resolving the problems associating with populations without selection. The selective breeding of F. chinensis was initiated in 1998 by Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, using pond-cultured and wild stocks as the base populations. In order to develop a new variety with both traits of fast growth and strong disease-resistance, a multi-trait selective breeding was proposed and conducted. After a successive selection of 11 generations, ‘Huanghai No. 2’ was bred, which possesses both growth and disease resistance traits was evaluated in 2008 (Kong et al., 2012). At present, ‘Huanghai No. 2’has been extended by Ministry of Agriculture of China as a main shrimp variety. Now it is mainly cultured in Shandong, Tianjin, Hebei, Liaoning, Jiangsu and other coastal areas of northern China, and has been well accepted by shrimp farmers. There have been some reports on the selection of F. chinensis, such as genetic parameter estimation (Tian et al., 2008), breeding model (Kong et al.,2008; Zhang et al., 2008; Luan et al., 2013), crossbreeding (Tian et al., 2006) and inbreeding (Luo et al., 2014).However, the difference of growth and survival performance between the breeding populations and wild populations has not been studied thoroughly.

The present study determined the differences of growth,survival rate, and genetic gain among bred populations of‘Huanghai No. 2’ and wild populations of F. chinensis by family construction, common environmental testing and statistical analysis in order to provide basic data for further breeding of Chinese shrimp.

Shrimp were harvested after 70 days of communal rearing. They were identified (by family) from the tag codes,counted, and individually weighed.

2 Materials and Methods

2.1 Populations

Four populations of F. chinensis included selected population for growth (SP_BWT) and selected population for WSSV resistance (SP_RW) separately constructed according to the rank of the single trait breeding value after testing growth and WSSV resistance of ‘Huanghai No.2’, and Bohai wild population (WP_BH) and Huanghai wild population (WP_HH) constructed by parent shrimps captured from Bohai Sea and Yellow Sea.

2.2 Family Construction

The artificial insemination technology was adopted to construct the family of each population according to mating scheme. The family was cultured with the standard operation procedures. The female shrimps with mature gonad were put into separate spawning bucket. The fertilized eggs were incubated at 14℃, and a random sample of about 5000 nauplii each family were stocked in separate larvae-culture tanks (200-L). The larvae were cultured with commercial micro-pellets, as well as Chaetoceros spp. microalgae, rotifer and artemia. Four hundred post-larvae were randomly selected each family and transferred to separate large tanks (3 m3) for continual rearing.

The absolute growth rate (AGR) of 4 populations was calculated by:

2.3 Trait Measurement

The results of average survival rate of four populations are shown in Table 2. Survival rate of SP_BWT was the highest, 85.38%, and that of WP_BH was the lowest,76.32%. x2 testing showed that the average survival rate of SP_BWT had highly significant difference with that of WP_BH (P ＜ 0.01), and there had a significant difference between the survival rate of SP_RW and that of WP_BH(P ＜ 0.05).

For harvest body weight, the following linear mixed effects model (LME) was fitted to estimate the least square means of different populations of F. chinensis by Predict command of ASReml software.

Tagged shrimps each family were divided and put into two 20 m2 concrete ponds at breeding station of Yellow Sea Fisheries Research Institute. The average water temperature was 26℃. The salinity was 30 g L−1. The shrimp were cultured with constant aeration, and a daily water exchange from 5% to 30%, depending on the shrimp growth stage. The food consisted of 38%–42% protein and 5% of the pond shrimp biomass.

他从网上调出了一个网页，上面写着“公众接遇赔偿费制度”。这项制度是在1963年开始实施的，距今已有半个多世纪的历史了。

2.4 Data Collection and Analysis

SPSS is used to do elementary data arrangement and factor analysis, including the average value, the maximum value, the minimum value, standard deviation and coefficient of variation. The boxplot was drew with ggplots package of R software.

The number of families established for SP_BWT, SP_RW, WP_BH and WP_HH were 10, 12, 14 and 4, respectively.

where Wb and We refer to the initial weight and final weight, respectively, t is days for rearing.

敏捷型的BIM团队的构建须领先其他项目资源、软硬件环境。根据某一职能，只获取最合适的定岗成员。随后逐个激活团队成员，将大量管理资源先行投射到成员的调集、招募和培训。必要的话，弃守传统项目启动流程，比如模型中心文件的建立。千万不要陷入固有思维——但凡更复杂、更昂贵、算力更强的设备就是当期最有效率的资源。最大优先级，先将团队的运作调动起来，务必要在团队基本凝成后再配置、补齐最合适的资源。

The survival rate of families each populations are shown in Table 3. Survival rate of SP_BWT families were all more than 80%, the highest family survival rate was 94.74%, and average survival rate was the highest among four populations, which was 85.57%. The average survival rate of SP_RW families was also high, which was 82.85%. For WP_BH families and WP_HH families, survival rate ranged from 71.88% to 81.82%, and from 72%to 82.76%. The coefficients of variation of survival rate of families of four populations ranged from 3.20% to 5.90%, indicating that survival rate has narrow genetic variation compared with growth trait.

3 Results

3.1 Descriptive Statistics for the Growth and Survival Rates of Four Populations

The descriptive statistics for the growth and survival rate of the four populations are presented in Table 1 and Table 2. As shown in Table 1, the SP_BWT had the highest average body weight (17.51 g), and WP_HH had the lowest average body weight (16.00 g). The coefficient of variation of body weight of four populations were high,ranging from 32.67% to 35.25%, which indicated that the selected population have greater genetic variation and still have great potential for further breeding.

After 4 weeks of rearing, shrimp body length reached 4± 1 cm. At least 20 shrimps each family of 4 populations were randomly selected and tagged with elastomer of four different colors (Northwest Marine Technology). The elastomer was injected into three areas of the last abdominal segment of the shrimp. The combination of different colors and positions represented the identification code of each family. The average initial body weight of each family was collected during tagging period.

Table 1 Descriptive statistics for the growth and survival rate of four populations of F. chinensis

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Table 2 Survival rate of different populations of F. chinensis

Population Initial number Survival number Survival rate (%)SP_BWT 253 216 85.38 SP_RW 302 250 82.78 WP_BH 418 319 76.32 WP_HH 99 78 78.79

3.2 Descriptive Statistics for the Growth and Survival Rate of Families of Four Populations

The results of harvest body weight of different families of four populations are shown in Fig.1. The mean, median,first quartile, third quartile, minimum, maximum and outlier values of harvest body weight of different families are shown in Fig.1 by boxplot. The range of harvest body weight of families of SP_BWT, SP_RW, WP_BH and WP_HH was 9.67–20.70 g, 11.62–20.06 g, 11.31–17.62 g,10.33–16.45 g, respectively. It can be seen that there are some differences in average harvest body weight and dispersion degree of weight among different families.

where yijk represents the weight of the kth shrimp; µ is the overall mean; Popi is the fixed effect of the ith group;Agek is the covariate of age from the kth shrimp;Familyj(Popi) is the random effect of the jth family nested within the ith group; and eijk is the random residual error of the kth individual.

Fig.1 The boxplot of harvested weight of different families of four populations of F. Chinensis.

Table 3 Survival rate of families in four F. chinensis populations

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3.3 Absolute Growth Rate of Family in Four Different Populations

Different absolute growth rate (AGR) of families in four populations is shown in Table 4. In SP_BWT population, family 798F had the highest growth rate, 0.25 g d−1,while family 807F had the lowest 0.1 g d−1. AGR of Family 798F was 150% higher than that of family 807F.Maximum AGR of families of SP_RW, WP_BH and WP_HH was 0.22 g d−1, 0.2 g d−1 and 0.2 g d−1, respectively,while the minimum was 0.13, 0.14 and 0.14 g d−1, respectively. There were similar difference between the maximum and the minimum of AGR among other three populations. Average AGR of family in the four populations were 0.19, 0.18, 0.17 and 0.16 g d−1, respectively, showing a declining trend. It can be seen that AGR of family was different in each population. Families with slower AGR were found in selected populations, while there were families with faster AGR in wild populations.

“三十年前我送你母亲一块玉佩，和我这块一模一样。那时，我在你们老家当知青。”范坚强下乡时，爱上一个当地女青年。1978年，他考上一所美术学院，结果因画裸体女模，不久即以强奸罪下了狱。那时，他们的儿子刚刚满周岁。那个女青年再也不愿意理他，后来甚至搬了家。以后，范坚强多次寻找她未果。再后来，虽然找到了，她也不肯再见他。她不是恨他坐过牢，是恨他因为强奸而坐牢。那个女青年就是一杭的母亲。一杭从来没有从母亲嘴里得到关于父亲的半点消息。当范坚强说起这段往事时，他被震惊了。

Table 4 AGR of families of four populations

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3.4 Realized Genetic Gain on Harvest Weight of F. chinensis

The least square mean of harvest weight of four populations is shown in Table 5. The least square mean of harvest weight of SP_BWT was the highest (17.50 g); and that of WP_HH was the lowest (13.03 g). Compared with WP_BH, harvest bodyweight of SP_BWT increased by 19.54%, and that of SP_RW increased by 8.67%. Compared with WP_HH, the harvest bodyweight of SP_BWT increased by 34.31%, and that of SP_RW increased by 22.10%. The result suggest that selection works well in the breeding program of F. chinensis.

Calculated t(35.5)0.05 and t(35.5)0.01 of least square mean were 2.030 and 2.724, respectively. The t of least square mean of SP_BWT and WP_BH, and SP_BWT and WP_HH was 3.09 and 3.16, being highly significant (P ＜0.01). The t of least square mean of SP_RW and WP_HH was 2.09, indicating that the two populations were significantly different (P ＜ 0.05).

目前，国内外所比较常用的对石油产品的低温性能指标进行检测的方法有两种：（1）直接检测方法；（2）间接检测方法[1]。但是，直接检测方法的检测结果准确性和一致性较差，仪器的自动化程度较低；而间接检测方法需要建立大量数据库和模型库，不便于形成独立的仪器。因此，结合电学阻抗技术所具有的简单适用，方便快捷的优点，本文通过采用电学阻抗技术建立一种快速的石油产品低温性能指标检测方法。

Table 5 Realized genetic gain of harvest weight of F.chinensis populations

Note: The former values of genetic gain and percentage are compared with WP_BH, and the latter two are compared with WP_HH.

Selective reaction Population Number of families Number of individuals Least square mean (g)Genetic gain (g)Percentage(%)SP_BWT 10 216 17.50 2.86/4.47 19.54/34.31 SP_RW 12 250 15.91 1.27/2.88 8.67/22.10 WP_BH 14 319 14.64 – –WP_HH 4 78 13.03 – –

4 Discussion

4.1 Effect of Breeding on Growth Trait

The main aim of breeding is to select excellent individuals by individual selection or mass selection from natural populations. Some excellent economic traits become outstanding and stable through continuous selection,forming a new variety (Lou, 2001). In the past few decades, a great progress has been made in the selection of breeding techniques, and a large number of animal and plant varieties and strains have been bred by selective breeding techniques. In general, aquatic animals, especially fish and crustaceans, have higher genetic variation than farmed animals in land. The genetic variation of growth of farmed animals in land varied between 7% and 10%, while that of fish and crustaceans varied between 20% and 35%. Therefore, high genetic variation of aquatic animals provides more possibility of increasing aquaculture production. GIFT tilapia is a successful example of aquatic animal breeding. After 3 generations, harvest weight of GIFT tilapia was 18% higher than that of local strains in China, and over 58% higher than that of indigenous strains in Thailand (Dey et al., 2000). After 6 generations, growth rate of GIFT tilapia was 85% higher than that of base population (Eknath, 1998). Yang (2008)carried out a selection for growth rate and morphological characteristics of rainbow trout with mass selection method. After 3 generations of selection, average daily weight gain rate is 5.7% and 12.2% higher than that of G2 and G1, respectively. Dong et al. (2011) successfully cultivated new breed Fu Rui Cyprinus carpio by using family selection based on quantitative genetic analysis. After 5 generations of selection, growth rate of Fu Rui Cyprinus carpio was over 20% higher than that of control families.Li et al. (2009) obtained the breeding population of macrostoma Micropterus salmoides by individual selection.Results showed that body length and weight in 2 breeding groups increased more obviously than those of control group after three generations of selection, which were 25.32% and 23.42% for daily weight gain rate.

The genetic breeding of shrimp has been carried out late, but it has developed rapidly in recent years, and has bred a series of elite varieties, such as ‘Huanghai No. 1’,‘Huanghai No. 2’ of F. chinensis, ‘South Tailake No. 2’of Macrobrachium rosenbergii, ‘Kehai No. 1’, ‘Zhongke No. 1’, ‘Zhongxing No. 1’ and ‘Guihai No. 1’ of Litopenaeus vannamei. Especially in L. vannamei breeding, a large number of genetic breeding researches have been carried out in recent years (Tan et al., 2017; Zheng et al.,2016; Sui et al., 2016; Hu et al., 2015). Goyard et al.(1999) compared the growth of Penaeus stylirostris between breeding population and non-breeding population after four generations, which showed that the weight of breeding population increased by 18%. Brad et al. (2002)found that the weight of L. vannamei increased by 21%after 1st generation of selection. Cao et al. (2015) found the growth rate of L. vannamei was 7.11% higher than that of control population at the 3rd generation.

In this research, the effect of breeding in F. chinensis was obvious. Realized genetic gain of SP_BWT compared with WP_BH and that of SP_BWT compared with WP_HH were 19.54% and 34.31%, respectively. Realized genetic gain of SP_RW compared with WP_BH and that of SP_RW compared with WP_HH were 8.67% and 22.10%, respectively. The realized genetic gain on harvest weight of SP_BWT was higher than that of SP_RW.The differences of least square mean between SP_BWT and WP_BH, and SP_BWT and WP_HH were all very significant (P ＜ 0.01), and the difference of least square mean between SP_RW and WP_HH was significant (P ＜0.05), but that between SP_RW and WP_BH was not.Such discrepancy may be caused by the difference of the places that two wild populations were captured, and of the genetic background and a smaller number of families structured by WP_HH.

It can be observed from the boxplot of harvest weight of families that the discrete degree and the average harvest weight of families in each population were different.The AGR of different populations and families were different. Family 798F had the largest AGR and Family 807F had the lowest. The largest AGR was 150% higher than the lowest. The average AGR showed a descending trend. It can be concluded that more breeding families with good growth advantage will be gained by constant family breeding. In addition, relatively high coefficient variation ranged from 32.67% to 35.25%, showing that the potentiality of breeding is large for further selection.

车子过了坪地，到了富地岗，进入了一片空旷地带，没有人家，没有路灯，漆黑漆黑地，静得怕人。夜风一吹，密密树林里发出沙沙响声，仿佛要向车子扑过来。女孩说，一听到这声音我就怕，要不是深惠公路在修路，打死我也不走这个道。

4.2 Effect of Breeding on Survival Rate

The survival rate of aquatic animals can be improved by selective breeding, and the most researches focused on the survival rate of resistant trait currently. Chen et al.(2010) studied the ability of anguillarum-resistance of families in cynoglossus semilaevis. The differences of survival rate of families for anguillarum-resistance in cynoglossus semilaevis was significant, which varied between 15.1% and 79.25%. Cao et al. (2012) studied the heat-resistance of turbot families, discovering that the difference of survival rate on heat-resistance among families was very significant. Brad et al. (2002) performed a selective breeding for anti-TSV (Taura Syndrome Virus)of L. vannamei, and found that the survival rate was improved by 18.4% after the selection for one generation.Gao et al. (2012) reported that the survival rate of breeding population in M. rosenbergii was improved by 7.76%compared with non-breeding population. In this study, our findings showed that during the whole culture period the survival rate of SP_BWT was much higher than that of WP_BH (P＜0.01), the survival rate of SP_RW was higher than that of WP_BH (P ＜ 0.05), and there was no significant difference among other populations (P ＞ 0.05).It can be observed that there is a certain difference among families in four populations, with the highest survival rate of 94.74% and the lowest of 71.88%. The coefficients of variation of survival rate among families in four populations were lower than that of harvest weight, which were 4.89%, 3.20%, 4.24% and 5.90% for SP_BWT, SP_RW,WP_BH and WP_HH, respectively. According to the above results, it can be seen that a series of measures should be taken, such as the large-scale family selection,high selection intensity and increment of selection index of survival rate, in order to improve the selective efficiency of survival rate.

In this study, the breeding families of F. chinensis were constructed through artificial insemination and standard cultivation technology of seeding. The differences of growth and survival rate among different populations and different families within one population were compared and analyzed. The results showed that compared with the wild populations, the breeding populations of F. chinensis have the significant growth and survival advantages,which still can be improved further by new methods. This result provides the important basic data for the next step of selective breeding in F. chinensis.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Nos. 31372523 and 31302 180), the Scientific and Technological Innovation Project Financially Supported by Qingdao National Laboratory for Marine Science and Technology (No. 2015ASKJ02),the Taishan Scholar Program for Seed Industry, the Shandong Provincial Natural Science Foundation (No. ZR20 14CQ001), the Special Fund for Postdoctoral Innovative Project of Shandong Province and Central Public-Interest Scientific Institution Basal Research Fund of the Yellow Sea Fisheries Research Institute (No. 20603022015013),and the China Agriculture Research System (CARS-48).

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