环境因子对大黄鱼耳石锶元素富积的影响

通过设计3个温度(18℃、22℃、26℃)×3个盐度(17、25、34)×3个锶元素组(1x、2x、3x)来研究环境因子对大黄鱼(Larimichthys crocea)耳石中锶元素沉积的影响。结果表明:不同温度条件下,耳石中Sr/Ca值与海水中的Sr/Ca值均呈线性关系;温度和盐度对耳石锶分配系数均具有显著的促进作用;锶元素浓度对耳石锶分配系数具有显著的抑制作用;影响耳石Sr/Ca值的环境因子中,海水Sr/Ca值的影响最大,温度的影响其次,盐度的影响最小;温度、盐度和锶元素浓度差异较大时,对耳石锶分配系数都具有显著的交互作用;在没有添加锶元素的实验组(低锶组)中,温度(18℃和26℃)和盐度(17和34)对耳石锶分配系数具有显著的交互作用;水温较高(26℃)时,锶元素浓度和盐度对耳石锶分配系数具有显著的交互作用。     

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。     

富锶水体处理对大黄鱼耳石和肌体中锶含量的影响

利用富锶水体处理的大黄鱼(Larimichthy scrocea)耳石元素标记是小规格鱼体规模化标记的一种技术手段,而标记完成后鱼体中的锶残留量是否符合食品食用安全是增殖放流评估中重要一环。通过开展富锶水体对大黄鱼鱼苗的浸泡标记实验,探究受试鱼苗耳石Sr/Ca值对富锶水体标记过程的响应方式,研究耳石元素指纹标记稳定性,分析标记过程对受试鱼苗肌体和主要脏器中锶含量的影响。结果表明:经为期7d、锶浓度含量3倍于天然海水的富锶水体的浸泡标记,受试鱼苗在特定耳石区段的Sr/Ca值显著增大,形成了与对照组个体在该耳石区段Sr/Ca值上的极显著差异(P<0.01);该差异不随时间的推移而减弱,可视做上述处理过程所产生的耳石元素指纹标识。浸泡标记处理后,受试鱼苗肌肉、鳃、肝脏和肾中的锶含量均显著高于对照组(P<0.05)。但随着时间的推移,锶含量逐渐下降;在天然海水中暂养59d后受试鱼苗肌肉和上述脏器中的锶含量均可衰减至对照组的水平。     

盐度对大黄鱼成活、生长和耳石金属元素的影响

为解决大黄鱼（Larimichthys crocea）面临着海水养殖病虫害感染加剧、海岸带土地局限性和水环境污染等问题,最终实现内陆工厂化低盐养殖,采用缓慢降盐法,将大黄鱼在室内不同盐度中养殖,研究不同盐度对大黄鱼成活率与温度、生长性能和耳石金属元素组成的变化的影响。试验周期6个月（180 d）,每个试验组设置3个重复,每组2万尾;海水盐度由24直接降至8,再以日均2的幅度将盐度降至6和4,然后以日均1的幅度继续将盐度降至2,最终将大黄鱼养殖在盐度分别为2、4、6、8、24的环境中;每天投喂2次颗粒饲料,每次投喂量为鱼体重的2%～5%,并视摄食情况酌情调整。结果显示,大黄鱼室内养殖成活率随着水温的升高而降低,水温28℃时,盐度24的海水养殖组全部死亡,水温30℃时,盐度2养殖组成活率（68.8±2.89）%极显著高于其他养殖组（P<0.01）;低盐养殖组的质量绝对增加率、绝对增长率、增积量和肥满度等生长指标在后期均优于盐度24养殖组;耳石金属元素锰（Mn）、钙（Ca）和锶（Sr）及Sr/Ca与盐度呈现正相关关系（P<0.05）,而Fe、Co和Ba元素变化者没有规律性。     

南海鸢乌贼耳石微量元素差异性分析

文章通过激光剥蚀电感耦合等离子体质谱法(laser ablation inductively coupled plasma mass spectrometry,LA-ICP-MS)测量南海鸢乌贼(Sthenoteuthis oualaniensis)耳石微量元素浓度,分析鸢乌贼耳石微量元素组成及与钙(Ca)元素比值的变化,探讨其存在的差异和与栖息环境之间的关系。结果表明,鸢乌贼耳石主要微量元素为Ca、锶(Sr)、钠(Na)、铁(Fe)、钡(Ba)、锰(Mn)。方差分析表明,鸢乌贼中型群和微型群及其性别间耳石微量元素浓度差异不显著(P0.05)。除Fe/Ca外,不同耳石区域微量元素浓度与Ca比值存在显著性差异(P0.01)。核心区Sr/Ca最高,随后逐渐降低,不同产卵群体和地理区域耳石Sr/Ca无显著差异(P0.05)。幼体期Sr/Ca与温度呈正相关性,与盐度呈负相关性,可以作为良好的温度指标。Na/Ca先增大后减小,暗区最高,核心区和后核心区Na/Ca在不同产卵群体间差异显著(P0.01)。Mn/Ca和Ba/Ca先减小后增大,暗区最低,随后分别在边缘区和外围区增大。成体期耳石Ba/Ca与盐度呈正相关,可以作为垂直移动的指标。Fe/Ca在不同产卵群体和地理区域中差异显著(P0.01)。分析认为,Na/Ca和Fe/Ca较为适合研究南海鸢乌贼不同群体的划分,Sr/Ca和Ba/Ca可用于推测鸢乌贼的栖息环境。     

毛里塔尼亚海域沙丁鱼耳石微量元素特征分析

鱼类耳石元素含量受栖息环境影响,因此通过分析鱼类耳石元素含量比值可以研究其栖息环境。根据2018年10月至12月在毛里塔尼亚海域(20°10′N～21°10′N、17°10′W～17°40′W)采集的219尾沙丁鱼(Sardina pilchardus),筛选58枚沙丁鱼耳石,利用激光剥蚀电感等离子质谱仪(laser ablation inductively coupled plasma mass spectrometry, LA-ICP-MS)测定不同年龄耳石元素含量并分析其比值的差异,探讨毛里塔尼亚海域沙丁鱼不同年龄栖息环境的变化情况。结果显示,毛里塔尼亚海域沙丁鱼耳石共检测到44种元素,主要为钙(Ca)、钠(Na)、锶(Sr)、铁(Fe)、镁(Mg)、钡(Ba)等;所有样本中不同性别沙丁鱼耳石主要微量元素(Na、Sr、Fe、Mg、Ba)含量与Ca含量比值差异不显著(P>0.05);毛里塔尼亚海域沙丁鱼耳石微量元素Na、Sr、Mg、Ba含量与Ca含量的比值核心区跟1龄区相比差异不显著(P>0.05),1龄区与2龄区、2龄区与边缘区差异显著(P<0.05)。研究表明...     

温度和元素浓度对Sr在褐牙鲆仔稚鱼耳石中的沉积影响

科学认识鱼类耳石中微量元素沉积与主要水环境因子的关系是基于耳石微化学方法重新构建鱼类生活史及反演其环境履历的重要前提。本研究以环境与耳石中重要元素Sr为例,研究在不同水温(16℃、19℃和22℃)和不同元素浓度(1×、2×和3×Sr)下Sr在褐牙鲆(Paralichthys olivaceus)仔稚鱼耳石形成生长过程中(孵化后15~93 d)的沉积(Sr∶Ca比)特征。结果显示,在不同水温下,耳石中Sr∶Ca比随水体中Sr浓度的升高呈线性增长,而元素分配系数(DSr)随元素浓度的升高先降低然后趋于稳定。在不同Sr浓度下,耳石中Sr∶Ca比及DSr均随水温升高呈增长趋势,二者在22℃时的值均显著高于在其他水温时的值。耳石中Sr沉积能够表征褐牙鲆仔稚鱼所经历的水环境中Sr浓度和水温的变化,可作为元素指纹应用于褐牙鲆早期生活史的重建和环境履历的反演。     

智利外海茎柔鱼耳石微量元素研究

茎柔鱼(Dosidicus gigas)是东太平洋海域重要的经济头足类,分布很广,群体结构和生活史过程复杂。头足类耳石生态信息丰富,多被用于生活史重建、群体划分等领域的研究。本研究根据我国鱿钓船2007和2008年在智利外海采集的茎柔鱼样本,利用激光剥蚀电感等离子质谱法(Laser ablation inductively coupled plasma mass spectrometry,LA-ICP-MS)分析了18枚茎柔鱼耳石的微量元素组成及其分布特性。分析表明,茎柔鱼耳石主要由48种元素组成,含量最多的前10位元素分别为钙(Ca)、锶(Sr)、钠(Na)、硅(Si)、钾(K)、镁(Mg)、钡(Ba)、锌(Zn)、锰(Mn)和锂(Li)。方差分析表明,不同性别间茎柔鱼耳石的Ca、Sr、K、Mg、Ba、Zn、Mn和Li含量不存在显著性差异,而Na和Si差异性明显;不同孵化群体间,除Zn和Mn不存在显著性差异外,其余元素的含量均存在显著性差异;茎柔鱼耳石的不同部位间,Sr、Na、K、Mg、Ba、Zn、Mn和Li的含量都存在显著性差异,而Ca和Si不存在显著性差异。研究表明,Sr、Ba、Mg、K和Li比较适合用于研究茎柔鱼群体的划分、洄游分布等方面的研究。     

水体钙离子质量浓度对褐牙鲆幼鱼鱼体和耳石元素成分的影响

在盐度30和水温20 ℃条件下,分别配制钙离子ρ（Ca2＋）质量浓度为200 mg·L-1（A组）、400 mg·L-1（B组,对照）、800 mg·L-1（C组）、1 600 mg·L-1（D组）和3 000 mg·L-1（E组）的人工海水,研究了水体ρ（Ca2＋）对褐牙鲆（Paralichthys olivaceus）幼鱼鱼体和耳石元素成分的影响。经60 d养殖发现褐牙鲆鱼体中仅钙（Ca）、锌（Zn）和铜（Cu）质量分数差异不显著（P〉0.05）;鱼体中磷（P）、钠（Na）、镁（Mg）、锶（Sr）、铁（Fe）、锰（Mn）和镍（Ni）质量分数随水体ρ（Ca2＋）的增加而下降。不同ρ（Ca2＋）对褐牙鲆幼鱼耳石长、宽、长宽比和耳石质量影响显著（P〈0.05）。低浓度A组耳石长和耳石宽显著低于B组和C组,A组耳石长宽比（L/W）显著低于D组,A组的耳石质量显著低于B组和D组（P〈0.05）。其中w（Sr）随ρ（Ca2＋）的增加显著下降,锶/钙（Sr/Ca）比、镁/钙（Mg/Ca）比随ρ（Ca2＋）增加而下降。结果表明,水体ρ（Ca2＋）对褐牙鲆鱼体成分、耳石形成及组分产生明显影响,ρ（Ca2＋）能够影响鱼体和耳石元素的累积。     

信江发现溯河洄游型刀鲚的实证研究

利用电子探针微区分析技术,对2014年8月1日采自江西省余干县瑞洪镇信江(鄱阳湖水系五大河流之一)江段的刀鲚(Coilia nasus)的矢耳石进行了锶和钙的微化学分析研究。元素定量线分析表明,样品的锶钙比值(Sr/Ca×103)波动显著,不仅具有对应淡水生活的低值(Sr/Ca×1033),而且出现了对应于海水生活的高值(3Sr/Ca×1037),显示出其典型的溯河洄游特征。耳石Sr含量的面分析结果与之相同,均具有对应淡水生活的低值(蓝色)区域和海水生活的高值(绿色)区域。这两种耳石微化学类型首次直观地证实,目前距长江河口约1000 km的信江中存在洄游型刀鲚。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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 performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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).     

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.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.