黄颡鱼人工繁殖及苗种培育技术的初步研究

２０００年５～６月共计催产黄颡鱼３批,计重５７ｋｇ,♀２０９尾,♂２２２尾,采用ＰＧ、ＬＲＨ－Ａ２、ＨＣＧ、ＤＯＭ中的２种或３种混和进行２次注射,水湿２５～２８℃,效应时间为１５～２０ｈ,共计产黄颡鱼卵２０．８万粒,经４８～７０ｈ孵化出苗４８ ０００尾,平均催产率、受精率、孵化离分别为３０．４％、５１．５％、４４．５％,经过１５～２０ｄ的培育,投喂水蚤和碎鱼肉浆培育成２～３ｃｍ的黄颡鱼鱼苗２０ ０     

太湖花夏花鱼种培育

一、试验材料１．鱼苗来源：夏花鱼种培育试验所用鱼苗，系由将天然亲鱼及人繁后代池塘培育成可催产的成熟亲鱼，经人工催产、受精、孵化而获得。２．培育池塘：夏花鱼种培育试验池塘为普通的养鱼池塘。面积０．４～３．５亩，水深０．８～１．２米，分新开挖塘和老鱼塘。试验塘在放养太湖花鱼苗前均按常规方法用生石灰消毒清塘。３．鱼苗放养：夏花鱼种培育试验的鱼苗放养均在每年的４月中旬５月上旬进行。每批试验即在受精卵孵化出膜后第４～５天放养，放养密度在２．８万～２２．２万尾／亩。二、培育方法１．鱼苗下塘：培育试验采用“半…     

斑Hu人工繁殖技术研究

采用单一或混合使用ＰＧ、ＬＲＨ－Ａ２和ＨＣＧ的方法，对池塘人工养殖７年的斑Ｈｕ亲鱼进行８批１９组人工催产，收集鱼卵１５１９９０粒，催产率达１００％；采用人工受精的方式获得受精卵１０６４５０粒，受精率５８．２％～８２．５％，平均值达７０％；使用小型孵化环道池、孵化网片及玻璃培养缸共１２个，孵出全长１．２～１．５ｃｍ鱼苗及玻璃培养缸共１２个，孵出全长１．２～１．５ｃｍ鱼苗３３８０８尾，孵化率８．２％～     

鳜苗种大批量繁育技术和工艺的研究

１９９３年在涨渡湖催产鳜亲鱼７组，产卵率１００％，获卵４５万粒。受精率７７．８％，孵化率８５．７％，获鱼苗３０万尾。经用孵化环道培育成夏花２９．５万尾；环道和产卵池培育成寸片２１．４２万尾。选择１ｋｇ以上的适宜规格鳜亲鱼强化培育是提高怀卵量和卵子质量及提高受精率、孵化率、苗种成活率的重要措施，采用环道流水培育苗种效果较好。开口饵料鱼以鳊最好。     

鳜鱼种大批量繁育技术和工艺的研究

１９９３年在涨渡湖催产鳜亲鱼７组，产卵率１００％，获卵４５万粒。受精率７７．８％，孵化率８５．７％，获鱼苗３０万尾。经用孵化环道培育成夏花２９．５万尾；环道和产卵池培育成寸片２１．４２万尾。选择１ｋｇ以上的适宜规格鳜亲鱼强化培育是提高怀卵量和卵子质量及提高受精率、孵化率、苗种成活率的重要措施，采用环道流水培育苗种效果较好。开口饵料鱼以鳊最好。     

双齿围沙蚕人工育苗生产性试验

介绍了双齿围沙蚕育苗生产的全过程。６￣７月份,利用对虾育苗室及其设备,采捕自然海域上浮的异沙蚕体,孵化密度５０￣１００万粒／ｍ＾３,经３５ｄ培养,幼体平均体长１．５（０．５￣３．０）ｃｍ,１３６ｍ＾２出苗量４５５万条,平均３２６２５条／ｍ＾２。三刚节幼虫至四刚节幼虫成活率７０％,四刚节幼虫至底栖成活率４９．４％,底栖后至出池成活率４７．９％。     

淡水白鲳人工繁殖技术的研究

淡水白鲳在海南地区露天养殖条件下，经强化培育亲本，确定性腺成熟指标，选择适当药物和剂量进行催产，创造适宜的孵化条件可获得较高的化产率、受精率和孵化率。１９９５年３—５月共计催产批计２２８组次，催产率、受精率和孵化率平均为８０．５％。６０．３％、７８．５％，共计获鱼苗１５００万尾。催产剂以ＰＧ、ＨＣＧ、ＬＲＨＡ和ＤＯＭ四种中三种或四种组合使用效果较好而稳定。     

南方大口鲶的人工繁殖及育苗试验

用ＨＣＧ、ＰＧ共催产５批２１尾雌亲鱼，１７尾全产。在雄鱼性腺成熟好的情况下，♀：♂＝２：１较合适，受精率可达８０％以上，适宜孵化水温１７￣３０℃，最好用曝气自来水，水泥池培育大口鲶苗效果比池塘好。     

鳜鱼养殖技术（三）

３鳜鱼的苗种培育３．１夏花培育近年来,鳜鱼苗种培育技术不断提高,培育方式也多种多样,由最初的池塘培育到人工控制条件下的工厂化育苗。现在较理想的培育方式有:孵化环道（桶）育苗、网箱育苗、水泥池育苗和小型土池育苗等。生产上,往往将两种或两种以上形式相结合进行。３．１．１培育方式３．１．１．１水泥池微流水培育水泥池规格一般为４ｍ×６ｍ×８ｍ,设有进排水装置,采用微流水的方法。主要用于培育开口３天后的鳜鱼苗,放养密度为２０００～３０００尾／。３．１．１．２土池培育鳜鱼长到２．０～２．５ｃｍ时,可以投放到小型池塘…     

乌鳢人工繁育技术

乌鳢人工繁育技术一、亲鱼选择和培育１．亲鱼选择亲鱼来自冬季干塘捕获，选择生命力强、体肥无伤的成熟乌鳢作亲鱼。为了便于催产操作，体重要求在０．５—１．０ｋｇ，雌雄比例大致为１：１。２．亲鱼培育选择好的亲鱼要专池培育，培育池面积以２—３亩最为适宜，水深１...     

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.