锶元素对黑鲷幼鱼耳石的标记效果分析

通过开展不同锶浓度养殖水体的黑鲷(Sparus macrocephalus)幼鱼耳石浸泡标记实验,验证利用该方法开展黑鲷幼鱼耳石指纹标记的可行性。研究结果显示:经7 d的浸泡标记,4个处理组幼鱼在特定耳石区位的Sr/Ca值均显著增加,形成了明显的耳石元素指纹标记;各标记处理组的标记成功率均为100%。单因素方差分析结果显示,各处理组和对照组黑鲷幼鱼在标记实验期间的生长率和死亡率均无显著性差异,表明该标记方法不会对受试黑鲷幼鱼产生显著负影响。浸泡标记处理可使受试幼鱼肌体内的锶浓度明显提升;标记结束17 d后,各处理组幼鱼肌体内的锶浓度大幅下降,18 mg·L~(-1)标记组幼鱼肌体内的锶浓度可降至对照个体水平。     

大亚湾黑鲷标志放流及回捕率调查

为评价大亚湾海域黑鲷(Acanthopagrusschlegelii)增殖放流效果,使用塑料椭圆标志牌(plasticovaltags,POTs),开展了黑鲷幼鱼标志保持率与生长实验。结果显示,背鳍鳍棘基部第4～6鳍棘下方5mm左右的背部肌肉为最适标志位置, 90 d后标志保持率为81.76%。POTs标志黑鲷幼鱼45 d内生长与对照组无显著性差异(P>0.05),而90 d后标志组生长显著缓于对照组(P<0.05)。并于2014—2016年每年1次在大亚湾开展黑鲷幼鱼标志放流试验。采用有奖回收方式进行标志鱼回捕,测量体长、体重,收集回捕日期、回捕地点、回捕方式等信息,整理分析相关数据。3年共放流标志黑鲷幼鱼60115尾,共2758尾回捕标志鱼被定置网、流刺网及垂钓捕获(总回捕率4.59%);大规格放流苗种回捕率高于小规格放流苗种;垂钓回捕鱼数量占总回捕数量的比例为62.08%。通过对反馈信息的分析,认为放流后的标志鱼最初主要沿湾内和湾外两个方向呈近岸辐射状扩散,最远扩散距离约70 km。放流后1～2个月标志黑鲷生长较慢,随后相对加快,放流5～7个月后,黑鲷幼鱼体长、体重分别增长59.51%～127.20%和322.75%～989.83%。结论认为,POT是黑鲷幼鱼体外标志的适宜选择;在研究海域,放流后的标志黑鲷更易于被垂钓方式捕获;丰富的食物和可供躲避敌害的空间是影响其扩散、生长的因素。     

荧光染料对短须裂腹鱼早期鱼苗的浸泡标记研究

为探究短须裂腹鱼(Schizothorax wangchiachii)早期鱼苗浸泡标记的合适荧光染料及标记条件,为短须裂腹鱼大规模标记放流及其效果评估提供参考,实验使用茜素络合物(AC)、茜素红S(ARS)、盐酸四环素(TC)、酸性茜素蓝B(AAB)、茜素黄GG(AYG)和钙黄绿素(CAL)溶液分别浸泡标记短须裂腹鱼早...     

拌饲投喂钙黄绿素对中华倒刺鲃幼鱼不同组织抗氧化酶活性和脂质过氧化的影响

为探究拌饲投喂方式下,钙黄绿素(calcein, CAL)对中华倒刺鲃幼鱼不同组织抗氧化水平和脂质过氧化的影响,以及正常投喂后的恢复情况,并进一步评价CAL拌饲投喂的毒性效应,实验将含有不同剂量CAL(0、2、8和32 g/kg)的饲料连续投喂中华倒刺鲃幼鱼16 d(即毒性积累实验),随后使用不含CAL的饲料投喂暂养32 d(即毒性消除实验)。毒性积累实验结果显示,在CAL拌饲投喂剂量 ≤ 32 g/kg的情况下,当累积投喂时间 ≤ 8 d时,过量的活性氧(ROS)能被中华倒刺鲃幼鱼的抗氧化系统成功清除,但更长的投喂时间(如16 d)可能产生一定的毒性效应,并导致鱼体肝胰脏和肾脏组织的氧化应激过度。毒性消除实验结果显示,经32 d正常投喂后,中华倒刺鲃幼鱼血清、肝胰脏和肾脏组织的大部分抗氧化酶指标、非酶抗氧化物、脂质过氧化产物基本恢复至安全水平。研究表明,当拌饲投喂剂量 ≤ 32 g/kg时,CAL对中华倒刺鲃幼鱼的毒性作用与累积投喂时间有着密切关系,且当使用 ≤ 32 g/kg的CAL拌饲剂量投喂标记中华倒刺鲃幼鱼时,CAL的累积投喂时间应控制在8 d以内,标记后的幼鱼应当至少暂养32 d。研究结果对CAL在鱼类荧光标记中的安全有效使用具有重要的指导意义。     

大黄鱼耳石锶标志技术

利用六水合氯化锶进行大黄鱼(Larimichthys crocea)幼鱼耳石的标记,探讨了锶元素对大黄鱼幼鱼耳石的元素指纹标记效果,分析了锶元素标记对大黄鱼幼鱼生长和存活的影响。结果表明:(1)阶段性倍增饲养水体中锶离子浓度可使标记组个体在特定耳石区段的Sr/Ca比值显著提升,形成与对照组个体和野生个体在该耳石区段Sr/Ca比值的显著差异(P0.01),标记组、对照组和野生个体在该耳石区段的Sr/Ca比值分别为(3.58±1.09)mmol/mol、(1.73±0.08)mmol/mol和(1.09±0.35)mmol/mol。此区段形成的Sr/Ca比值峰值可视作标记组个体的耳石锶元素人工标记。(2)标志组和对照组大黄鱼幼鱼的生长速率和存活率均无显著性差异(P0.05),表明此项标记技术对受标个体的生长和存活状况不会产生显著负面影响,可用作大黄鱼增殖放流鱼苗的规模化标记手段。     

茜素络合物在青鱼幼鱼耳石上的标记效果评价

放流标记技术研究是支撑增殖放流效果评估的重要内容。该研究用质量浓度为100 mg·L-1的茜素络合物(ALC)对约2月龄的青鱼(Mylopharyngodon piceus)幼鱼进行48 h浸泡,随后移入正常水体中恢复续养20 d。对其3种耳石在可见光和不同的激发光下进行比较分析,评价了茜素络合物在不同耳石上的沉积情况与标记效果。结果表明,通过在可见光和不同的激发光下进行观察,其3种耳石上均可见明显的标记区,标记率达100%。在对标记鱼恢复续养20 d后发现,耳石上的荧光标记区强度仍很高,表现出了较好的标记效果。此外,相关标记的最佳检测光源为蓝色激发光,绿色激发光次之。微耳石是用于青鱼幼鱼耳石荧光标记观察的最适类型,同时也是用于时滞检测的最适类型,其次是星耳石。此外,将鱼体浸泡入茜素络合物溶液中至其在耳石上形成标记沉积,以及将鱼体移出浸泡溶液至其耳石上标记区域消失,均存在1 d时滞。     

不同标记方法对黑鲷苗种生长及存活的影响

该试验主要目的是探究体内体外两种不同的标记方法对于不同规格的黑鲷苗种生长及存活的影响。试验采用体外剪鳍法和体内PIT标记法,对大(平均体质量69.00 g)、小(平均体质量41.29 g)两种不同规格的黑鲷进行标记。分析在相同的养殖条件下,两种不同的标记方法对于黑鲷生长与存活的影响。试验结果表明,在为期25 d的试验中,在相同的生存条件下,大规格黑鲷体外标记组、体内标记组、空白对照组的存活率分别为56.67%、83.33%、93.33%,生长率分别为3.32%、15.82%、11.23%;小规格黑鲷体外标记组、体内标记组、空白对照组的存活率分别为100.00%、100.00%、96.67%,生长率分别为10.64%、22.31%、11.44%,从试验结果判断,体内标记(PIT标记)优于体外标记(剪鳍),在一定范围内,规格小反而更适宜进行标记。该试验结果为黑鲷的标志放流提供了理论依据。     

广东东江外来尼罗罗非鱼年轮特征及其影响因素

以养殖群体为对照,研究了广东东江外来尼罗罗非鱼(Oreochromis niloticus)鳞片、腹鳍棘、鳃盖骨、脊椎骨和矢耳石5种年龄材料的年轮结构特征。与养殖群体相比,整体上东江种群年轮的清晰度及对比度更高。结合周年水温数据,推测东江尼罗罗非鱼在1 3月份低温期形成1个年轮标志,而其副轮较多的特征可能与繁殖活动有关。在5种年龄材料中,以矢耳石的轮纹特征最为明显,且规律性强,而鳃盖骨和鳞片受副轮影响,可读性最低。5种年龄材料的可读性由大到小顺序为矢耳石、脊椎骨、腹鳍棘、鳃盖骨、鳞片。     

草鱼仔鱼耳石茜素络合物标记特征研究

草鱼(Ctenopharyngodon idellus)是我国主要增殖放流经济鱼种之一,探索有效的标志方法对其增殖放流的技术保障和效果评价无疑至关重要。本研究对草鱼仔鱼耳石进行了1 d茜素络合物(ALC)荧光标记,以确认该方法的可行性及适宜条件。结果显示,微耳石、矢耳石和星耳石均能被标记。标记环在可见光及荧光下均能被观察到。其中,后者使用蓝色激发光(WBS)观察效果最佳。总体上,微耳石的标记效果最好,矢耳石次之。ALC浸泡对鱼体的生存及生长无显著影响,耳石上荧光信号出现和消失与鱼体开始浸泡和结束均存在约12 h的时滞。浸泡标记过的实验鱼在经过长达60 d的恢复续养后,标记环仍清晰可见,表明ALC标记效果明显且可长期存在。该方法对草鱼仔鱼的增殖放流标记具有较强的可行性。     

基于耳石微化学特征甄别黑鲷放流群体和野生群体的初步研究

基于耳石微化学特征研究甄别黑鲷(Sparus macrocephalus)放流群体和野生群体的可行性,并根据该特征对象山港捕获的黑鲷成鱼进行了群体判别。研究结果显示,向天然海水中加入适当淡水后形成养殖海水,养殖海水的Ba离子浓度显著高于天然海水(P<0.05);养殖黑鲷的耳石核心位置的Ba/Ca比值(C)、全耳石Ba/Ca比值■及Ba元素变异系数(CVI)均显著高于野生黑鲷(P<0.05)。耳石上的Ba/Ca比值可作为识别养殖黑鲷和野生黑鲷的微化学标志。以此为标志对象山港捕获的20尾黑鲷成鱼进行群体判别,结果表明2尾黑鲷为放流群体。     

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).     

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.     

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.