南方大口鲶苗种自残现象探析

一、产生自残现象的主要原因１．饵料不足或不适口：饥饿是大口鲶发生自残现象的主要原因，饵料不足（育苗水体中浮游动物量低于每毫升水５个；或适口的饵料鱼水花与大口鲶苗种比小于１∶１）时，大口鲶在开食的第３天（此时规格尚且整齐）即开始互相残食（前期阶段主要是咬对方的尾鳍）。然而即使饵料充足，但若不适口（饵料规格过大或过小）也会导致自残现象的发生。因此，在养殖过程中必须投足适口饵料。２．苗种规格不整齐：全长８厘米的大口鲶能将全长５厘米的大口鲶完整地吞到胃中，可见，大口鲶可吞食全长占自身２／３的同种。因此饲…     

鱼类同类相残现象的研究现状

1 研究概况 在鱼类的生长发育过程中,常发生大个体、壮个体攻击、吞咬小个体、弱个体,致使被攻击者伤亡的现象,这就是鱼类的同类相残现象,有的文献也称为自残、互残、残杀、残食等。我国早在明代《本草纲目》中     

肉食性鱼类驯食技巧

肉食性鱼类在人工养殖条件下 ,因它们的摄食量大 ,并具有相互残食的习性 ,特别是在投饵供不应求的情况下 ,常发生相互撕咬 ,最后导致体弱幼小者被体强或体大者所吞食 ,造成成活率低 ,直接影响养殖效益。笔者经过多年的实践和探索 ,现将肉食性鱼类的驯食技巧介绍如下 ,以供养殖者参考。１驯食需从苗种开始鱼类属卵生 ,苗种阶段其食性较杂 ,当自身的卵黄被完全吸收后 ,便以水体中的浮游生物为食 ,随着生长发育 ,个体不断增大 ,消化器官和机能的逐渐完善 ,所食饵料开始偏向为单一性。因此 ,抓住苗种阶段食性较杂这个有利时机 ,驯食就容易得多。…     

关于河豚鱼的养殖之三:提高红鳍东方鲀幼鱼存活率的新方法

目前红鳍东方统育苗中存在的最主要的问题就是自相残食，自残是东方纯属鱼类的本性，从稚鱼阶段起自残现象逐步加剧，特别是全长达ZO～4Onlm的幼鱼阶段，生长迅速，摄食量增大，自相残食现象相当严重，是制约其育苗存活率的主要因素。国内现在一般采取增加投饵、分档养殖及降低放养密度等方法来减少自残的发生，但增加投饵及降低放养密度无疑会增加管理负担和降低水体利用。本实验在有效利用水体和方便日常管理的前提下，采用在培养地四角是挂剥离皮肤的花鲈，让幼鱼自由采食的方法，来提高其幼鱼阶段的存活率，实验取得比较理想的效果。…     

提高红鳍东方鲀幼鱼存活率的新方法

<正> 红鳍东方鲀属于鲀形目、鲀科、东方鲀属,俗称“河鲀”、“辣头”,其产品主要出口日本,经济效益很高,近年来养殖业发展迅速,育苗规模不断扩大。目前红鳍东方鲀育苗中存在的最主要的问题就是自相残食。自残是东方鲀属鱼类的本性,从稚鱼阶段起自残现象逐步加剧,特别是全长达20～40mm的幼鱼阶段,生     

不同规格的大口鲶苗种池塘培育效果比较

大口鲶主要分布于我国长江干、支流和少数通江湖泊中,属大型的经济鱼类。该鱼生长快、肉味鲜美、广温耐寒 ,但由于该鱼属肉食性鱼类 ,当饵料缺乏或个体大小不整齐时 ,会出现互相残食现象 ,影响鱼种阶段的成活率 ,挫伤了养殖者的积极性。１９９９年５月１２日至６月１２日我们进行了该苗种的养殖试验 ,旨在解决大口鲶苗种培育技术难题。现将试验结果报告如下。１材料与方法１．１试验鱼苗系自繁并经小型水泥池培育７～１５ｄ后的鱼苗 ,全长１５～３５ｃｍ。试验池４口 ,每口面积６６７ ,石砌水泥护坡 ,池底平坦 ,淤泥深５～１０ｃｍ ,水深…     

裂腹鱼池塘养殖技术初探

裂腹鱼又称雅鱼 ,属鲤形目 ,鲤科 ,裂腹鱼亚科 ,裂腹鱼属 ,主要分布在我省西部的青衣江流域以及新疆、青海、西藏等省的高原河流和湖泊之中。裂腹鱼属冷水性鱼类 ,喜栖息于底质为沙滩、且水温较低的山区河流中 ,尤以河道弯曲处较多 ,天然环境下以食着生藻类、底栖水生昆虫及其幼虫为主要食物 ,也食少量高等植物 ,吞食小型鱼虾类。裂腹鱼肉肥质嫩 ,富含脂肪 ,味道鲜美 ,生长速度快 ,个体较大 ,常见个体为 0 5～ 2公斤 ,最大个体重达 10公斤 ,清蒸“裂腹鱼”是四川省的主要名菜之一 ,裂腹鱼是我省重要的野生经济鱼类 (2 0 0 0年被我省列为省…     

暗纹东方鲀苗种互相残食原因及控制措施

在暗纹东方鲀苗种培育过程中常常因仔鱼互相残食而导致成活率大大降低,严重时导致育苗失败,因此,防止暗纹东方纯互相残食是苗种生产应采取的重要措施.本文就其残食的表现、原因及相应的应对措施作一总结,供养殖者借鉴.……     

怀头鲇人工系列及苗种培育技术

怀头鲇又名六须鲇、东北大口鲇。地方名叫怀子、怀头，是一种大型肉食性珍稀鱼类，自然水域已经很难捕到，目前已被列为濒危鱼类。近几年，怀头鲇人工繁殖技术取得了突破性进展，并且积累丰富的经验，使得该物种得到了有效保护。催产率、受精率、孵化率已分别达90％、85％、90％以上。但在水花至夏花阶段的苗种培育过程中，所存在的自残问题仍未得到解决，成活率仅为15％左右。导致苗种生产不稳定，供不应求，制约了怀头鲇养殖的产业化进程。笔者根据几年来所进行的怀头鲇人工繁殖及苗种培育试验。总结出以下经验，供同仁参考。     

水的混浊度与黑鲷稚鱼互残现象的关系

<正> 黑鲷 Sparus macrocephalus 是一种广泛分布于我国沿海的名贵海产鱼类和优良的海水增养殖品种。目前,随着人工繁殖技术的不断完善,苗种存活率得到迅速提高,出苗量已达到生产性规模。但在育苗过程中,体长1厘米以上的稚鱼,常出现较明显的互残现象,尤其个体出现大小分化,在饵料不足、稚鱼处于饥饿状态下,这种现象更为显著。弱小个体的眼睛、腹部、鳍等部位常受到攻击,造成大批死亡。然而在生产上,当育苗水体变得混浊时,自相残杀造成的死亡率又会下降。因此,我们设想,在水体中投     

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 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).     

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.     

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.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.