基于水温的鳜与鲢配套催产模式研究

为解决汉江上游流域鳜饵料鱼的配套问题,建立鳜与鲢配套催产模式,分析了水温对鳜和鲢人工繁殖中效应时间、孵化时间、开口时间等的影响,了解鳜和鲢人工繁殖各时间段与水温的相关性。结果表明:鳜孵化时间和开口时间与水温(18~28℃)显著相关,受精卵孵化时间(y)与水温(x)的关系式为y=41 058x~(-2.142 4),R~2=0.995 2,仔鱼开口时间(y)与水温(x)的关系式为y=-0.099 6x~2-5.226 0x+266.02,R2=0.961 4;鲢的效应和孵化总时间(y)与水温(16℃x32℃)的关系式为y=0.051 4x~2-4.924 4x+129.91,R~2=0.978 2;鳜、鲢配套催产时间(y)与水温(x)的关系式为y=-0.151 0x~2-0.301 6x+136.11。研究表明,在水温18~28℃条件下,可根据水温计算出鲢的催产时间,为在鳜人工繁育生产中进行开口饵料鱼的精准配套提供参考。     

钝缀锦蛤形态性状对活体质量的影响

为研究钝缀锦蛤形态性状和活体质量之间的关系,随机选取的150粒野生钝缀锦蛤作为试验材料,分别测量其形态性状(壳长x1、壳宽x2、壳高x3)和活体质量(y),采用相关分析和通径分析方法计算形态性状对活体质量的通径系数和决定系数。相关分析结果表明,钝缀锦蛤的形态性状和活体质量之间的相关系数均达到极显著水平(P0.01),其中壳宽与活体质量相关系数最大(0.970)。通径分析结果表明,壳宽对活体质量的直接作用最大(0.677),其次为壳高(0.184),最小为壳长(0.151)。决定系数分析结果与通径分析结果相一致,壳宽是影响活体质量的主要因素。多元回归分析建立了估计活体质量的回归方程:y=-160.195+0.726x1+4.307x2+0.894x3,r2=0.960。该研究结果为钝缀锦蛤的人工选育和种质资源保护提供参考。     

温度和水流对扁吻鱼胚胎发育的影响

探讨了温度及水流对扁吻鱼(Aspiorhynchus laticeps)胚胎发育的影响。结果表明:在水温15~25℃条件下,扁吻鱼胚胎发育均可以完成,并且温度x与发育时间y呈负相关关系,y=667.72 e-0.0996x,R2=0.9829;与积温的关系为y=-91.017x+3662.3,R2=0.7996。胚胎发育的适宜水温为15~23℃,最适水温为15~21℃。孵化期间辅助于一定的充气条件可缩短出苗时间、提高出苗率,降低畸形率。     

倒刺鲃的胚胎发育及水温对胚胎发育的影响

对倒刺鲃的胚胎发育进行连续跟踪观察,并探讨了水温对其胚胎发育的影响。结果表明:水温(25±0.5)℃时,孵化时间为53.43 h;胚胎发育过程中出现克氏囊。水温21～33℃条件下,倒刺鲃的胚胎均能孵化,水温(x)与孵化时间(y)成极显著的负相关关系:y=235.72 e-0.056 6x,P<0.01;水温与积温的关系为:y=7 519.4x-0.519 2,P<0.01。孵化率(y)与水温(x)相关关系式为:y=-1.665 5x2+88.621x-1 091.5,由曲线方程可以推算出胚胎发育的适宜水温范围为23.4～29.8℃,通过曲线求导数推算极值的方法,求得胚胎发育的最适水温为26.6℃。     

倒刺鲤的胚胎发育及水温对胚胎发育的影响

对倒剌鲃的胚胎发育进行连续跟踪观察,并探讨了水温对其胚胎发育的影响。结果表明：水温（25&#177;0．5）℃时&#183;孵化时间为53．4．3h;胚胎发育过程中出现克氏囊。水温21～33℃条件下。刨剌鲃的胚胎均能孵化&#183;水温（x）与孵化时间（y）成极显著的负相关关系：y=235．72e^-0.0566x,P〈0．01;水温与积温的关系为：y=7519．4x^-0.5192.P〈0．01。孵化率（y）与水温（x）相关关系式为：y=-1．6655x^2＋88．621x—1091．5．由曲线方程可以推算出胚胎发育的适宜水温范围为23．4～29．8℃．通过曲线求导数推算极值的方法。求得胚胎发育的最适水温为26．6℃。     

短蛸的早期生长特征

对孵化后1~50日龄短蛸(Octopus ocellatus)幼体的体重、全长、腕长及胴长进行测量,观察并分析其早期生长变化特征。在水温为22℃~24℃的养殖条件下,初孵短蛸平均全长为10.03 mm。11日龄幼体开始营底栖生活,以此为分界线划分为浮游期和底栖期。 结果显示,1~11日龄浮游短蛸体重增长为立方函数增长类型,y = 0.0001x3 – 0.0019x2 + 0.0098x + 0.0409;11~50日龄的底栖短蛸体重增长为指数函数增长类型,y = 0.0284e0.092x。在1~50日龄短蛸幼体的生长过程中,体重(g)与全长(mm)呈立方函数关系,y = –8e–07x3 + 0.001x2 – 0.011x + 0.099;全长(mm)与腕长(mm)呈线性关系,y = 1.314x + 4.952;体重、全长及腕长分别与日龄呈立方函数关系,y = 6e–05x3 – 0.003x2 + 0.036x – 0.03、y = 0.0004x3 + 0.002x2 + 0.307x + 10.604、y = 0.0004x3 – 0.007x2 + 0.364x + 4.205。通过研究短蛸幼体的生长发育特征,从而加深了对幼体生长的了解,并为短蛸人工繁育的研究提供参考依据。     

水温和盐度对大菱鲆稚鱼存活的影响

采用突然改变温度和盐度的方法,试验不同水温和盐度对大菱鲆稚鱼存活的影响。试验结果表明,水温为15.0~18.0℃、盐度为28~32,大菱鲆稚鱼存活率最高;用曲线回归的方法求出24 h内存活率与温度的关系式,其回归方程为y=-0.5506x2 18.4970x-53.13,依此得到大菱鲆稚鱼的高、低起始致死温度为26.54℃和7.06℃。依同样方法得到24h内存活率与盐度的回归方程为y=-0.4353x2 23.4226x-213.81,高、低起始致死盐度为37.76和16.05。经t检验显著相关(P<0.01)。     

水温对额尔齐斯河银鲫幼鱼耗氧率及窒息点的影响

为鱼类养殖生产和苗种运输过程中溶解氧的科学调控提供理论依据,该试验采用密闭呼吸室法测定了20、22、24、26、28、30℃水温下额尔齐斯河银鲫幼鱼的耗氧率和窒息点。结果表明,水温在20～30℃时,额尔齐斯河银鲫幼鱼的耗氧率随水温的升高而显著上升(P<0.05)。水温为20℃时耗氧率最低,为0.263 mg/(g·h);水温为30℃时耗氧率最高,为0.571 mg/(g·h)。耗氧率与水温的拟合方程为:y=0.0093x^2-0.0027x+0.2604(R^2=0.9896)。额尔齐斯河银鲫幼鱼的窒息点在20～30℃水温下,随水温的升高而上升,其中水温为20℃时窒息点最低,为0.947 mg/L;水温为30℃时窒息点最高,为1.713 mg/L。水温和窒息点的回归关系方程式为:y=0.0271x^2-0.0629x+1.0452(R^2=0.9116)。     

偏顶蛤胚胎和幼虫发育及温度对其浮游幼虫生长和发育的影响

在室内条件下,人工诱导偏顶蛤(Modiolus modiolus)产卵并在显微镜下对其胚胎和浮游期幼虫的形态进行连续观察和拍照,并采用实验生态学的方法,研究温度对其浮游期幼虫生长和发育的影响。结果显示,偏顶蛤亲贝人工催产时,以流水刺激4 h,阴干12 h为宜。偏顶蛤卵呈圆形或卵圆形,沉性卵,卵径为(82.6±3.2)μm,精子鞭毛型,全长约50μm。在水温19~21℃下,偏顶蛤受精卵发育至D形幼虫(壳长104.0μm±4.3μm)、匍匐幼虫(壳长255.8μm±15.0μm)和早期稚贝(壳长329.1μm±5.8μm)分别历时20.5 h、20 d和36 d。水温是影响偏顶蛤幼虫生长和发育的主要因素之一,幼虫适宜水温为15~20℃,15℃组幼虫畸形率显著低于20℃组,生长率20℃组最高达5.4μm/d;水温25℃和30℃下,幼虫畸形率均显著高于15℃组和20℃组,并分别在第6天和第4天全部死亡。相对于高温而言,偏顶蛤幼虫对低温的耐受能力更强。本文旨在为偏顶蛤繁殖生物学和苗种繁育技术提供基础资料。     

日本海神蛤人工繁殖及早期生长发育

为探究日本海神蛤规模化人工苗种繁育的可行性,在国内首次开展了日本海神蛤人工繁殖及早期生长发育研究,结果显示,日本海神蛤繁殖盛期为5月和10月,单次产卵量为300~500万粒/枚,卵径为75~85μm。春季人工将水温升至18.6~19℃, 15~18日龄幼虫生长缓慢,壳长生长率仅为1~3μm/d。其他各日龄幼虫壳长生长率为9~15μm/d。日本海神蛤变态后,再经过30~40 d培育,平均壳长可达（4.94±0.93）mm,稚贝壳长生长率为50~167 μm/d,平均苗种产量为2 695粒/m3。秋季水温17.4~13.2℃条件下,日本海神蛤幼虫相对春季生长发育较慢,经过148 d的培育,稚贝平均壳长可达（2.88±0.47）mm,平均苗种产量为6 666粒/m3,再经室外池塘中间育成后,可培育平均壳长（13.22±2.39）mm幼贝。比较发现在我国北方秋季可培育出适于底播养殖的大规格苗种,且培育成本较低。本研究为我国日本海神蛤苗种繁育、高效养殖及资源修复提供了科学依据。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).