Induced Spawning of Striped Snakehead,Channa striatus,Using Ovatide

ABSTRACT

An experiment was investigated to evaluate the effects of different doses of a new spawning agent Ovatide on induced spawning of striped snakehead, Channa striatus. Nine matured females with swollen abdomen and 18 male fishes with body weights ranging from 750 to 900 g, were randomly assigned to three treatment groups. Fishes in each group were administered 0.2, 0.4, and 0.6 mL of Ovatide/kg body weight, respectively. Each breeding set consists of two males and one female. Partial spawning response was observed when the fishes were administered with 0.2 mL/kg BW of Ovatide. Complete spawning was noticed in the medium (0.4 mL/kg BW) and higher (0.6 mL/kg BW) dose administered groups. The latency period and number of eggs spawned ranged from 23 to 27 hours and 1,764 to 7,096, respectively. No significant difference (P > 0.05) was noticed in the fertilization and hatching rate between the medium and higher doses of Ovatide tested. Thus, C. striatus could be successfully induced to spawn using a synthetic gonadotropin-releasing hormone with a dopamine antagonist at the dose of 0.4 mL/kg BW under captive conditions at 29 ± 1.5°C.     

Tolerance of Snakehead Channa striatus to Ammonia at Different pH

Tolerance of snakehead Channa striatus to ammonia was tested at three pH levels (8.0, 9.0. and 10.0) in experimental tanks. At pH 8.0, ammonia LC50 estimates for snakehead at 24, 48, 72, and 96 h were >205.7, >203.5, 152.6, and 107.3 mg total ammonianitrogen (TAN)/L (or >10.3, >10.2, 7.6, and 5.4 mg NH₃-N/L), respectively. At pH 9.0, ammonia LC50 estimates at 24, 48, 72, and 96 h were >52.4, 62.8, 56.1, 43.4 mg TAN/L (or >18.0, 21.6, 19.3, and 14.9 mg NH₃-N/L), respectively. At pH 10.0, ammonia LC50 estimates at 24, 48, 72, and 96 h were 25.7, 21.6, 20.3, and 18.7 mg TAN/L (or 21.6, 18.1, 17.1, and 15.7 mg NH₃-N/L). respectively. Our data indicate that the tolerance of snakehead to ammonia was associated with pH. Thus, we recommend that snakehead should not be subjected to prolonged exposures of NH₃-N concentration more than 0.54 ma at pH 8.0, more than 1.49 mg/L at pH 9.0, or more than 1.57 mg/L at pH 10.0.     

Effect of lipid levels on the reproductive performance of Snakehead murrel,Channa striatus

Present study aimed to determine the optimum dietary lipid level in snakehead murrel channa striatus broodstocks. Triplicate groups of fish were fed for 240 days with isonitrogenous experimental diets with increasing lipid levels (100, 140, and 180 g kg^?1), using fish oil and soybean oil as the lipid sources with the ratio of (1:1). Weight gain, GSI, fecundity, oocyte diameter and number of mature oocyte were found to be significantly higher in the group fed with diet containing 180 g kg^?1 lipid level. Muscle fatty acid profile showed a significant increase in LA (18:2n‐6), LNA (18:3n3), total PUFA, n‐6 and ArA (20:4n‐6) in fish fed with diet containing 180 g kg^?1 lipid. Increasing lipid level up to 180 g kg^?1 resulted in significant increase in PUFA (LA & LNA), lc‐PUFA (EPA, DHA, ArA), total PUFA, n‐3 and n‐6 series in ovary and liver of female C. striatus.     

Effects of Feed Application Rates on Growth, Survival, and Feed Conversion of Juvenile Snakehead Channa striatus

Growth, survival and feed conversion ratio of juvenile snakehead Channa striatus were evaluated when fed a dry, formulated feed (50% crude protein) at 24 ± 1 C. Six daily feed application rates were used (0%, 5%, 10%, 15%, 20%, and 30%), as a percentage of fish body weight, with three replicates per treatment. After 29 d, final weights were all significantly greater ( P < 0.01) than initial weights, except for the 0% application. Feed applications higher than 5% did not result in increased growth ( P > 0.05). Feed conversion ratio was 0.99 at 5% feed application, and 6.3 at 30% feed application. Fish survival was increased by providing formulated diet, but no further improvement was found when feed applications exceeded 5%. Cannibalism was reduced by providing formulated feed, but it was unavoidable when substantial differences in fish size existed, even when feeding ad libitum . Our results indicate that the optimal feed application rate is close to 5% body weight/d for juvenile snakehead.     

９种交配组合鳢的人工繁殖试验

运用人工催产的方法进行了9种交配组合鳢的人工繁殖试验,9种组合来源于乌鳢(Channa argus)、斑鳢(C.maculate)和杂交鳢(Hybrid snakehead)彼此之间的交配繁殖.结果表明,无论采用何种孵化方式,9种交配组合所产卵的受精率和孵化率高低顺序基本一致,且各组合间都存在显著差异.交配组合斑鳢(♀)×斑鳢(♂)、斑鳢(♀)×杂交鳢(♂)、杂交鳢(♀)×斑鳢(♂)及杂交鳢(♀)×杂交鳢(♂)在繁殖过程中,其受精率和孵化率高于其他组合,具有较强的繁殖优势,但其子代的生产性能优势还有待进一步研究.孵化方式对受精卵的发育与孵化有重大影响,其中以微流水孵化方式时的受精率和孵化率最高、孵化效果最好.雄亲鱼的重复催产次数会影响受精率及孵化率,一般以重复利用2～3次为宜.     

网箱养殖乌鳢试验

乌鳢Ophiocephalusargus,俗称乌鱼、黑鱼、蛇头鱼等,属鲈形目、鳢科,为典型的凶猛肉食性鱼,对不良水质、水温、缺氧有很强的适应力,生长迅速、活鱼运输方便。乌鳢营养丰富、肉质细嫩、肉味鲜美,具有生肌补血、去瘀生新、滋补调养、加速伤口愈合等功效,是一种经济价值很高的淡水鱼,一直被视为病后康复和老幼体弱的健身补品,因此,日益受到消费者的青睐,售价高、销路好,出口到港澳成为抢手,市场需求量越来越大。我国乌鳢产量主要来源于天然水域,远远满足不了市场的需要。1990年代后期,人工养殖业开始起步,主要是池塘精养。为探索乌鳢在水…     

Emaciation of pond-cultured snakehead, Channa striatus (Fowler)

Abstract. A new disease condition which may affect up to 20% of a population has been recognized in pond cultured snakeheads, Channa striatus (Fowler). Clinically, affected fish are inappetent and severely emaciated; histologically and ultrastructurally, emaciated pond reared snakeheads display extensive striated myofibrillar and sarcoplasmic degeneration and necrosis with inflammatory changes.     

Economic Analysis of Alternative Snakehead Channa striata Feed

The use of low-value small-sized fish (LVSSF) both as aquaculture feedstuff for snakehead and for human consumption in Vietnam and Cambodia could result in demand outstripping supply as human population and aquaculture production grow. Replacing LVSSF for snakehead aquaculture with pelleted feed would reduce the pressure on stocks of LVSSF. This study addresses the economics of this replacement strategy for snakehead culture in Vietnam. Economic engineering methods were used to assess the effects of pelleted feed for low, medium and high-productivity scenarios. The study compared net present values (NPV), internal rates of return (IRR) and differences in NPV between farms using pelleted feed and those using LVSSF. It also included sensitivity analyses that related NPV and IRR to increased snakehead prices. Results demonstrated strong economic incentives for high-productivity farms to use pelleted feed. However, pelleted feed was too expensive for medium- and low-productivity farms. NPVs were more sensitive to reductions in the cost of pelleted feed than to increases in the cost of LVSSF or the cost of capital.     

乌鳢网箱繁育技术研究

2001年3月至2002年10月。在1．73hm^2池塘利用小网箱集中进行乌鳢苗种人工催产孵化，培育过程中按鱼苗规格大小分级到大型网箱中培育大规格鱼种，进行规模化大批量生产。2002年度催产60组乌鳢亲鱼。生产乌仔58万尾。培育大规格鱼种55700kg，利润219860元。     

白乌鳢的人工繁殖试验

在自然水温24-25℃时，采用HOG LRH-A2 2次注射性成熟白乌鳢亲鱼。效应时间为20～26h。雌雄配比为对配(1：1)时，产卵受精效果较好。在水温24-25℃的静水中孵化。经36-40h出膜。出膜后培育45 d，苗种全长为4．3-8．6cm。     

池塘集约化养殖乌鳢高产试验

利用8hm^2池塘进行集约化养殖乌鳢高产试验，投放乌鳢鱼种47894kg，经过14个月的养殖，获成鱼407640kg，其中乌鳢389640kg，平均单产48705kg／hm^2，折合纯收入10．36万元／hm^2；并在苗种选择、饲养管理。特别是鱼病防治方面提出了一些独到的见解，经济效益显著。     

PCR结合变性高效液相色谱快速检测发酵乳酸杆菌

采用多聚酶链式反应结合变性高效液相色谱技术建立了发酵乳酸杆菌的快速检测方法.以编码发酵乳酸杆菌Lactobacillus fermentum延伸因子(EF-Tu)基因为靶基因设计引物,优化PCR体系,以加氏乳酸杆菌等26株试验菌株做特异性检测;并将标准菌株稀释成不同梯度,做灵敏度检测.试验结果表明,该方法有很好的特异性,且灵敏度高,检测限可达到100CFU/ml.     

乌鳢规模化繁育技术

2000年6月催产50组成熟亲鱼，网箱静水孵化，共产卵89．5万粒，受精度90％，孵化率98％，培育成3－4cm的鱼种48．3万尾，总投入19480元，产出12．435万元，投入产出比为1：6．38。     

乌鳢营养需要的初步研究

采用正交试验L9（3^4)的方法，以蛋白质、脂肪、糖类和有效磷为试验因子，配制了9种试验饲料进行饲养试验。乌鳢对4种营养素的适宜需要量为：蛋白质40%、脂肪8%、糖类16%、有效磷0.8%。根据乌鳢肌肉的氨基酸含量，计算出蛋白质含量为40%时饲料中9路必要氨基酸含量。     

Control of Aeromonas hydrophila Infection in Spotted Snakehead, Channa punctatus, by Solanum nigrum L., a Medicinal Plant

The present study describes the potential of black nightshade, Solanum nigrum , to control Aeromonas hydrophila infection in spotted snakehead, Channa punctatus . Similar sizes of Ch.   punctatus were grouped into three categories as follows: control (injected with sterilized water), Ae.   hydrophila infected   +   untreated, and Ae.   hydrophila infected   +   treated with S.   nigrum leaf extract. Hematological parameters (white blood cell [WBC], red blood cell [RBC], hemoglobin [Hb], and packed cell volume [PCV]) were analyzed in these fishes once every 5   d from Days 5 to 30 postexposure. Preliminary antibacterial assay reported that leaf extracted with ethyl acetate had the maximum inhibition compared to other parts of the plant (i.e., berries and whole plant) or when extracted with other solvent extracts (chloroform and ethanol). Except for WBC count, all other parameters showed a declining trend from Day 5 onward and reaching to a minimum on Day 30 in Ae.   hydrophila -infected fish, whereas the WBC count increased. The infected fish treated with S.   nigrum leaf extract reported a significant reversion to normal RBC, WBC, Hb, and PCV levels and the skin ulceration recovered within a short period. The antiulcer potential of the medicinal plant as described in humans may be extended to the fish population.     

乌鳢精养塘日常管理要点

从水质管理、科学投饲、疾病防治3个方面阐述了乌鳢池塘精养中应注意的问题，“六定两勤”是科学投喂的关键，水质调控与疾病防治是养殖成功的保证。     

Influence of different sources and levels of dietary protein and lipid on the growth,feed efficiency,muscle composition and fatty acid profile of Snakehead Channa striatus (Bloch, 1793) fingerling

Nine isoenergetic (18.5 kJ g⁻¹) diets were formulated, in a 3 × 3 factorial design, by varying three levels of dietary protein (350, 400 and 450 g kg⁻¹) at each of three levels of dietary lipid (65, 90 and 115 g kg⁻¹) accordingly. Each diet was hand fed two times daily for 8 weeks to triplicate homogenous groups of eight fish (average weight 3.34 ± 0.02 g) per tank connected to a recirculation system. Results showed that the feed efficiency and growth performance significantly (P<0.05) increased with increasing protein level at the two lower lipid levels (65 and 90 g kg⁻¹), respectively, as indicated by indices such as %weight gain, specific growth rate, protein efficiency ratio, feed conversion ratio and feed intake, but did not at the highest lipid level (115 g kg⁻¹). The muscle polyunsaturated fatty acids (PUFA) content declined with increasing dietary protein level at the lipid levels producing the highest growth, suggesting that the utilization of PUFA influences growth. Whereas the muscle monounsaturated fatty acids level was generally lower than the dietary levels in all the treatments tested, indicating preferential catabolism for energy, the muscle saturated fatty acids level was comparatively higher than in the diets, indicating selective deposition. Docosa hexaenoic acid (22:6n3, DHA), which was very low in the diet and in the initial fish, was higher in the muscle of some of the treatments, indicating the ability of Channa striatus to desaturate and elongate short‐chain PUFA to long‐chain HUFA, due to the availability of dietary 18:3n3 and 20:5n3 (the precursors for DHA biosynthesis). It could be concluded, based on the results of this trial, that a diet formulated to contain 65 g kg⁻¹ lipid and 450 g kg⁻¹ protein, with a gross energy of 18.5 kJ g⁻¹ and a dietary n3/n6 PUFA ratio of about 0.1, is sufficient to promote good feed efficiency and growth performance in C. striatus fingerling.     

Influence of dietary lipid/protein ratio on survival,growth, body indices and digestive lipase activity in Snakehead (Channa striatus,Bloch 1793) fry reared in re‐circulating water system

Nine isoenergetic (18.5 kJ g^?1) diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg^?1) for each of three lipid levels (65, 90 and 115 g kg^?1), respectively, and fed twice daily for 8 weeks to fish of mean initial weight 3.34 ± 0.02 g reared in a re‐circulatory water system. Temperature, pH and dissolved oxygen (DO) were maintained within the range 28–30 °C, 5.6–6.8 and 4.82–6.65 mg L^?1 respectively throughout. Results show that fish survival was better in the groups fed 65 g kg^?1 lipid while growth performance (% weight gain, WG; specific growth rate, SGR) and nutrient utilization (feed conversion ratio, FCR; protein efficiency ratio, PER; protein intake, PI) in the 65/450 and 90/450 g kg^?1 treatments were similar and significantly (P < 0.05) higher than in fish fed the other lipid/protein ratio combinations. The body indices monitored (Hepatosomatic index, HSI and viscerosomatic index, VSI) were similar among the treatments whereas intestinal lipase activity was not significantly (P < 0.05) affected by increase in dietary lipid and protein levels. Carcass composition showed that dietary protein level affected body protein content positively in the 65 and 90 g kg^?1 lipid treatments, but dietary lipid level did not affect body lipid content. A lipid/protein ratio of 65/450 g kg^?1 is considered adequate for good growth performance and survival of Channa striatus fry.     

池塘网箱养殖乌鳢试验

在宿鸭湖水库管理局水产试验场进行了池塘网箱养殖乌鳢试验。试验池面积16亩,设置6×11×2米单层聚乙烯网箱13只,箱内放乌鳢种3.2万尾,池内放其它鱼类21600尾,至年底共收获乌鳢31468.7公斤,其它鱼类12157.2万公斤,产值47.5万元,利润27万元,投入产出比1∶2.3。