长江斑鳜的人工繁殖和苗种培育研究

长江斑鳜(Siniperca scherzeri Steindachner)的催产和受精卵孵化受天气、温度和水温影响较大。长江斑鳜的种质资源锐减,本研究有利于保护长江斑鳜的种质资源,人工繁殖采用人工催产、自然受精和人工孵化的方法。选择团头鲂幼苗为长江斑鳜幼苗的开口饵料,随后以鲤和团头鲂的夏花为主要饵料鱼,辅以从江河中捕获的野杂鱼夏花。在不同水温条件下,效应时间和受精率明显不同。当水温在(20±2)℃时,效应时间约为32h,受精率大于80%;水温低于18℃时,效应时间明显延长,受精率也较低;水温20～24℃时孵化时间约125h,孵化率均超过90%。长江斑鳜幼苗出膜后30～56h开始主动摄食。幼苗全长(L;mm)与日龄(D;d)的线性关系为L=3.244+0.926D,r=0.9940。长江斑鳜的人工繁殖和苗种培育为后续研究及人工养殖提供了资料和参考。     

长江斑鳜的人工繁殖和苗种培育研究

长江斑鳜（Siniperca scherzeri Steindachner）的催产和受精卵孵化受天气、温度和水温影响较大。长江斑鳜的种质资源锐减,本研究有利于保护长江斑鳜的种质资源,人工繁殖采用人工催产、自然受精和人工孵化的方法。选择团头鲂幼苗为长江斑鳜幼苗的开口饵料,随后以鲤和团头鲂的夏花为主要饵料鱼,辅以从江河中捕获的野杂鱼夏花。在不同水温条件下,效应时间和受精率明显不同。当水温在（20±2）℃时,效应时间约为32h,受精率大于80%;水温低于18℃时,效应时间明显延长,受精率也较低;水温20～24℃     

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。     

昆明裂腹鱼全人工繁殖技术初探

<正>文章对昆明裂腹鱼全人工繁殖过程中的亲鱼催产效应、受精卵孵化等方面的内容进行了研究,结果表明,采用干法和半干法相结合的人工授精,共获得受精卵27.10万粒,受精率53,98%。采用孵化槽孵化,经过170小时~180小时,共孵化鱼苗11,32万尾。催产期间,水温平均16,5℃,效应时间为46小时。孵化水温13℃~18℃,溶氧6,5mg/L时,平均孵化时间176小时,最早174小时。     

瓦氏黄颡鱼人工繁殖技术研究

瓦氏黄颡鱼在池塘生态环境条件下人工培育亲鱼、人工繁殖.产卵季节为每年的5中旬～7月上旬,产卵水温为20～30℃,最佳产卵水温为23～28℃,催产效应时间水温20～30℃为40～52小时.流水水泥池中流水孵化,孵化必须在室内光照500～800Lx条件下进行,孵化出膜时间水温20～30℃为47～70小时.人工繁殖的产卵率、受精率、孵化率均达到90%以上.     

欧洲丁(鱼岁)的人工繁殖技术

欧洲丁(鱼岁)人工繁殖的亲鱼以3～4龄较好,个体要求雌鱼到达400g,雄鱼到达250g以上;催产时间(鹰潭地区)为4月下旬-5月中上旬为好;适宜水温为18～30℃,最适水温为25～28℃,32℃以上时产卵率、受精率和孵化率都较低;催产激素可选择混合激素,剂量为50μg/kg LHRH-A2和5mg/kg DOM合剂;催产方法以两针注射法为好,针距为8～10h;效应时间(水温25℃时)为11～16h;产卵既可自然产卵也可人工授精,孵化一般在网箱中充氧孵化即可,有条件的地方可以实行脱粘后在环道或孵化漕中进行孵化.三年的最高产卵率87%、受精率91%、孵化率93%.     

花提早人工催产及孵化试验

2008年4月16-28日在浙江湖州地区进行了花于水温15℃条件下的人工催产生产性试验。用常规催产剂和方法,催产花亲鱼540尾,其中雌亲鱼355尾、雄亲鱼185尾。试验结果表明:排卵率为91.5%,催产效应时间为29.5 h,群体排卵时间为2.5 h;受精率为98.7%;孵化鱼苗(下塘鱼苗)380万尾。与常规生产水温17～18℃以上催产情况比较,在水温15℃条件下,花也完全可以进行人工催产;除效应时间和孵化时间延长及卵膜难以溶解外,其排卵率、受精率、群体排卵时间和孵化率等均无明显差异。     

欧洲丁的人工繁殖技术

欧洲丁人工繁殖的亲鱼以3~4龄较好,个体要求雌鱼到达400g,雄鱼到达250g以上;催产时间(鹰潭地区)为4月下旬-5月中上旬为好;适宜水温为18~30℃,最适水温为25~28℃,32℃以上时产卵率、受精率和孵化率都较低;催产激素可选择混合激素,剂量为50μg/kg LHRH-A2和5mg/kg DOM合剂;催产方法以两针注射法为好,针距为8~10h;效应时间(水温25℃时)为11~16h;产卵既可自然产卵也可人工授精,孵化一般在网箱中充氧孵化即可,有条件的地方可以实行脱粘后在环道或孵化漕中进行孵化。三年的最高产卵率87%、受精率91%、孵化率93%。     

拉萨裂腹鱼胚胎适宜孵化水温研究

为探索拉萨裂腹鱼(Schizothorax waltoni)胚胎适宜孵化水温,提高胚胎受精率和孵化率,降低初孵仔鱼畸形率,设置5℃、9℃、12℃、14℃、16℃、18℃、20℃、22℃共8个温度梯度进行拉萨裂腹鱼鱼卵孵化实验,统计各温度下的胚胎发育速度、鱼卵受精率和孵化率、初孵仔鱼畸形率及形体指标。结果显示,拉萨裂腹鱼胚胎卵裂期发育最快,到囊胚期、原肠期、器官分化期及出膜期,每个发育时期积累时间逐渐增长;随温度的升高,胚胎发育时间缩短,发育速度加快。各温度条件下,胚胎发育时期与孵化时间均呈幂函数关系,孵化积温随温度升高呈现逐渐降低的趋势。水温9～18℃的鱼卵受精率较高,均超过90%;水温12～16℃的孵化率较高,均超过95%;水温9～16℃的鱼苗畸形率较低,均低于4%。初孵仔鱼全长与孵化温度呈二次多项式函数关系;不同水温的初孵仔鱼体高没有显著性差异,但卵黄囊体积先升高、后降低、再升高。研究表明,适当提高孵化水温能缩短胚胎孵化周期,但水温过高会影响胚胎孵化率,增加初孵仔鱼畸形率,影响仔鱼对营养物质的吸收利用以及器官发育分化。综合考虑胚胎孵化周期、孵化率、初孵仔鱼畸形率及形体指标,拉萨裂腹...     

棘胸蛙人工繁殖的研究

本文报道了应用生理生态相结合的方法成功地进行棘胸蛙人工繁殖的研究结果。福建地区,5月前后是棘胸蛙人工催产的最佳季节;在山涧流水式的产卵池中,注射LRH—A人工诱导产卵,有效剂量50—200微克/个,水温18—28℃,效应时间61.5—80小时,产卵率96.3％;应用激素人工诱导产出的卵球有良好的受精与发育能力,自行受精的卵球受精率71.9％,人工授精的卵球受精率81.9％;采用流水网箱孵化,平均孵化率可达70％以上(70.3—91.0％),平均水温20—26.5℃,孵化时间144—238小时,胚胎发育积温3816—4760度时;出膜后6—7天的幼蝌蚪,全长1.8—2.1厘米(S_(25)),具有主动摄食和游泳能力,可进行人工投饵养育。文中对不同种类激素人工诱导产卵效果差异问题进行了分析和讨论。     

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.     

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).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven,Hemitripterus americanus

The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg^-1) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown, suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose production. Epinephrine-mediated (10^-5M) glycogen breakdown and insulin-mediated (10^-8M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any glucagon (10^-7M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine indicates mobilization of carbohydrate reserves for endogenous use by the liver. Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by cortisol implantation. Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify the effects of glucagon or food-deprivation in this species.     

Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystem

Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three‐dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems.     

Effects of capture,loading density and transport stress on the mortality,physiological responses,bacterial density and growth of rohu <Emphasis Type="Italic">Labeo</Emphasis><Emphasis Type="Italic"> rohita</Emphasis> fingerlings

This study evaluated the effects of three levels of loading density (200, 300 and 400 g L⁻¹) and four levels of duration (1, 3, 6 and 9 h) on the mortality, plasma cortisol and chloride levels and growth of rohu Labeo rohita fingerlings in a transport simulation. While total immediate mortality was low (4–12%), delayed mortality was high (27–49%). Initial capture and handling were found to constitute the most stressful phase as indicated by elevated plasma cortisol. The levels of cortisol continued to rise at 6 and 9 h after transport, with the highest level observed at 9 h after transport. The level of plasma chloride fell after transport across all density levels and treatment durations. Specific growth rate (SGR, %/day) and total bacterial density (cfu/g) were not different between and within treatments, and between treatments and the controls. This study demonstrates that transport has a profound effect on the stress responses of rohu fingerlings. Although the level of immediate mortality was low, the higher level of delayed mortality has serious implications in terms of production inefficiency for grow-out farmers.     

The effects of introduced tilapias on native biodiversity

• 1. The common name ‘tilapia’ refers to a group of tropical freshwater fish in the family Cichlidae (Oreochromis, Tilapia, and Sarotherodon spp.) that are indigenous to Africa and the southwestern Middle East. Since the 1930s, tilapias have been intentionally dispersed worldwide for the biological control of aquatic weeds and insects, as baitfish for certain capture fisheries, for aquaria, and as a food fish. They have most recently been promoted as an important source of protein that could provide food security for developing countries without the environmental problems associated with terrestrial agriculture. In addition, market demand for tilapia in developed countries such as the United States is growing rapidly.
• 2. Tilapias are well‐suited to aquaculture because they are highly prolific and tolerant to a range of environmental conditions. They have come to be known as the ‘aquatic chicken’ because of their potential as an affordable, high‐yield source of protein that can be easily raised in a range of environments — from subsistence or ‘backyard’ units to intensive fish hatcheries. In some countries, particularly in Asia, nearly all of the introduced tilapias produced are consumed domestically; tilapias have contributed to basic food security for such societies.
• 3. This review indicates that tilapia species are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced. Thus, the authors have concluded that, despite potential or observed benefits to human society, tilapia aquaculture and open‐water introductions cannot continue unchecked without further exacerbating damage to native fish species and biodiversity. Recommendations include restricting tilapia culture to carefully managed, contained ponds, although exclusion is preferred when it is feasible. Research into culture of indigenous species is also recommended.

Copyright © 2005 John Wiley & Sons, Ltd.