浙江老虎潭水库后生浮游动物群落组成及其环境影响因子

为探究老虎潭水库后生浮游动物群落多样性变化,2014年5月至2015年2月按季度分4次对水库6个采样站点的后生浮游生物种类组成、密度与生物量、多样性指数以及9项水质理化指标进行了调查。结果表明,老虎潭水库共鉴定出后生浮游动物20属、34种,其中轮虫10属、22种,枝角类4属、6种,桡足类6属、6种;主要优势种为长肢多肢轮虫(Polyarthra dolichoptera)、裂足臂尾轮虫(Brachionus diversicornis)、萼花臂尾轮虫(Brachionus calyciflorus)、角突臂尾轮虫(Brachionus angularis)、圆筒异尾轮虫(Trichocerca cylindrica)、罗氏异尾轮虫(Trichocerca rousseleti)、长圆疣毛轮虫(Synchaeta oblonga)和长额象鼻溞(Bomina longirostris),且优势种的季节更替明显;密度和生物量季节差异显著,年均密度为27.79个/L,年均生物量为0.23 mg/L;丰富度指数和Shannon-Wiener多样性指数在4个季节间差异显著,夏季略高于其他3个季节;TLI指数显示,老虎潭水库全年各站点均处于中营养水平;冗余分析(RDA)表明,透明度、溶解氧、水温、高锰酸钾指数和p H是影响后生浮游动物群落动态变化的重要环境因子。     

涡河中下游浮游动物群落结构及水生态评价

浮游动物群落结构是定量描述河道水生态系统功能的重要指标,动物种类及现存量变化能灵敏地反映水域生态环境的动态变化。为探究涡河中下游浮游动物群落结构及其影响因素,于2016年12月至2017年9月分季度监测了其群落组成和水质变化,根据涡河中下游水闸的位置,将整个涡河划分为5个河段,每个采样河段均设置2个采样点,共计10个样点;采用浮游动物种类、密度、生物量和多样性指数,对涡河水体的营养状态和污染情况进行了评价,通过群落指标与水质指标的冗余度,识别群落结构的影响因子。结果表明:(1)涡河中下游4次采样共检测出浮游动物56种,其中原生动物13种,轮虫20种,枝角类13种,桡足类10种;(2)4个季度的生物量为0.12～8.87 mg/L,均值为1.78 mg/L;Shannon-Wiener多样性指数为0.22～3.17,均值为2.13;水体整体处于中度富营养状态,污染指数为中污型;(3)春季的浮游动物优势种数较其他三季高,春季多样性指数较夏冬略高,明显高于秋季;(4)义门镇采样点秋季多样性指数接近于严重污染状态,城西镇、高炉镇采样点秋季多样性指数均处于严重污染状态,广布多肢轮虫为3个采样点的绝对优势种,在水质治理中应引起重视;(5)冗余度分析表明,环境因子对浮游动物时空分布的总体变异解释度为60.70%,流速、水温和溶解氧是影响涡河中下游浮游动物群落结构的主要环境因子。     

武汉南湖浮游轮虫的初步研究

周年4次采样,在武汉南湖5个采样点共计鉴定出浮游轮虫22个种,主要优势种类螺形龟甲轮虫Keratella cochlearis、针簇多肢轮虫Polyarthra trigla、长三肢轮虫F ilina longiseta和暗小异尾轮虫Trichocerca pu-silla,均为富营养湖泊的指示种。轮虫季节变动明显,密度由高到低为:秋季2 987 ind./L,夏季1 440 ind./L,春季1 130 ind./L,冬季903 ind./L;生物量则依次为秋季1.04 mg/L、夏季0.50 mg/L、春季0.40 mg/L、冬季0.32 mg/L。轮虫的水平分布均匀,Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ站年平均密度依次为1 729、1 575、1 617、1 588和1 567 ind./L;生物量依次为0.61、0.55、0.57、0.56和0.55 mg/L。轮虫的Margalef多样性指数较低,在1.31~2.12之间。     

汾河太原段轮虫多样性及群落结构的动态变化

调查汾河太原段轮虫群落结构的时空变化,探讨轮虫群落结构动态变化规律及其与环境理化因子的关系,为汾河太原段浮游动物动态预测和多样性保护提供必要信息,从生态系统的角度客观评价水质污染状况与水体富营养化程度。在汾河太原段设置采样点7个,于2014年3-12月对轮虫和水体理化指标进行逐月调查。共检出轮虫98种,隶属3目21科33属。全年优势种是长肢多肢轮虫（Polyarthra dolichoptera）和螺形龟甲轮虫（Keratella cochlearis）。调查期间月均检出轮虫28种,轮虫丰度变化范围为153 ~ 1 440 个/L,生物量为0.08～0.89 mg/L;种类数、丰度和生物量均表现为枯水季较低,丰水季最高。群落结构相似性分析表明不同营养状态水体之间差异显著,轮虫丰度、生物量、Shannon-Wiener 多样性指数和Pielou均匀度指数均存在明显差异;中等营养条件的指示种为卵形无柄轮虫（Ascomorpha ovalis）和单趾狭甲轮虫（Colurella unicauda）,指示轻度富营养的指示种为柔软龟甲轮虫（Keratella delicata）,中等富营养水体的指示种则为臂尾轮属的种类。冗余分析结果显示环境变量对轮虫群落结构变异的解释率为 41.3%,水温、叶绿素a 、溶解氧、总氮等因子是影响轮虫时空分布的主要因素。轮虫群落结构特征可以指示水体的营养状态。     

淀山湖轮虫多样性及生物量时空变化

2004年1月至2006年12月逐月对淀山湖轮虫种类组成、生物量和生物密度的时空变化规律及其生物多样性进行了调查研究，并分析了轮虫密度和水温、叶绿素a的关系。经鉴定，共发现轮虫53种（属），优势轮虫包括针簇多肢轮虫Polyarthra trigla、角突臂尾轮虫Brachionus angularis、萼花臂尾轮虫Brachionus calyciflorus、螺形龟甲轮虫Keratella cochlearis、曲腿龟甲轮虫Keratella valga、晶囊轮虫属Asplanchna spp.、长三肢轮虫Filinia longiseta、椎尾水轮虫Epiphanes senta等，优势种的密度之和分别占当年度轮虫总密度的87.2、82.8和82.8%。3年轮虫平均密度和生物量分别为2514ind/L和2.94mg/L，2005年3月份St6轮虫密度高达11700ind/L。轮虫密度（ind./L）和生物量（mg/L）季节分布一致，均为春季（4862和5.45）>秋季（2300和3.45）>夏季（1773和1.88）>冬季（940和0.45）；在水平分布上，表现为湖心高、进水口和出水口较低、处于网围养殖附近的St3轮虫密度最低的变化趋势。各站点3年平均H为2.27（变幅为2.08-2.50），Marglef指数D平均为2.3（变幅1.1-3.8）。淀山湖轮虫密度和水体中的叶绿素a含量呈极显著相关，回归方程为：轮虫密度（ind./L）=521.6+64.11Chl.a (µg/L)（r=0.634, P<0.001）。     

粤东柘林湾甲壳类群落结构季节变化分析

基于2013年2月(冬季)、5月(春季)、8月(夏季)和11月(秋季)柘林湾拖网调查数据,分析了柘林湾甲壳类资源密度、种类组成和优势种、多样性的变化特征,并对甲壳类群落结构和环境因子的关系进行了研究。调查结果表明,甲壳类资源密度变化范围为30.094~199.048 kg·km~(–2);甲壳类出现53种,隶属于2目13科22属,主要优势种为口虾蛄(Oratosquilla oratoria)、宽突赤虾(Metapenaeopsis palmensis)、锈斑蟳(Charybdis feriatus)和哈氏仿对虾(Parapenaeopsis hardwickii)等;多样性指数变化范围为2.31~3.03,均匀度指数变化范围为0.55~0.8,物种丰富度指数变化范围为1.55~3.29。单因子相似性分析(ANOSIM)、聚类分析和非度量多维标度分析(NMDS)结果表明,柘林湾海域甲壳类群落结构存在明显的季节更替。相似性百分比分析(SIMPER)表明各季节典型种主要有口虾蛄、断脊口虾蛄(O.interrupa)等,分歧种主要有口虾蛄、红星梭子蟹(Portunus sanguinolentus)等。典范对应性分析表明,影响柘林湾海域甲壳类群落结构季节变化的主要环境因子依次为水温、p H和溶解氧。     

济南地区河流轮虫群落结构的时空动态研究

探讨轮虫群落结构及与水质环境因子之间的关系,为合理开发济南地区水资源以及水环境污染治理提供可靠依据。2014年5月(春季)、8月(夏季)和10月(秋季)分别对济南地区19个站点采样调查,分析不同季节轮虫群落结构的分布特征,应用香农维纳指数和均匀度指数评价济南地区水质健康状况,典范对应分析法判定影响轮虫群落结构的主要环境因子。济南地区水体共鉴定出轮虫17属38种,以龟甲轮属和臂尾轮属为主,春季、夏季和秋季轮虫种类分别为30、17和9种,轮虫密度平均值为114.4、10和8.3个/L。轮虫污染指示种20种,其中寡污带3种、寡污至β中污型5种、β中污性8种、α中污型2种、β-α中污型2种;轮虫污染指示种类占总种类数的52.63%,密度占77.99%;春季出现污染指示种15种,夏季和秋季分别为11种和8种。春季的优势种为卵形彩胃轮虫,夏季的优势种为萼花臂尾轮虫,秋季的优势种为萼花臂尾轮虫、卜氏晶囊轮虫、前节晶囊轮虫。香农维纳指数平均值分别为2.67、1.38和1.20;均匀度指数平均值分别为0.66、0.41和0.35。典范对应分析结果,主要影响南部、中部和北部地区轮虫群落结构的环境因子,春季为总氮、氨氮和硬度,夏季为高锰酸钾,秋季为总磷。综合评价济南地区水生态呈中度污染。     

石臼湖江苏段浮游植物群落结构特征及与环境因子的关系

分析石臼湖江苏段浮游植物群落结构及对环境因子的响应,以期探索浅水型湖泊浮游植物动态变化机制,为石臼湖水域生态环境监测与保护、生物资源调查提供基础数据。2012年10月至2013年8月,在石臼湖江苏段12个采样点进行了4次采样,调查浮游植物的群落结构及水环境因子,并通过冗余分析(RDA)对数据进行直接梯度排序,分析浮游植物群落结构对环境因子的响应。共发现浮游植物79种,隶属于8门53属,绿藻门21属39种,蓝藻门11属13种,硅藻门10属11种1变种1变型,裸藻门4属5种,甲藻门3属4种,隐藻门2属3种,金藻门1属1种,黄藻门1属1种。优势种(属)10种,冬季以对水温和光照有较好适应能力的硅藻为主要优势种群;春季优势种类较丰富,但优势度不高(0.03~0.09);夏、秋季节以小型丝状蓝藻占绝对优势。浮游植物总平均密度为28.93×106个/L,季节差异显著,峰值出现在夏季,冬季最低。多样性分析表明,石臼湖浮游植物的物种组成较丰富,然而种间分布不均,群落结构稳定性较弱。基于CANOCO的多变量分析表明:p H、溶解氧、透明度、氨氮、水温、电导率是影响浮游植物群落结构的主要环境因子。     

泸沽湖表层水体浮游动物种群结构及季节变化

2010年对泸沽湖表层水体的浮游动物进行了季节调查。结果表明:泸沽湖表层水体有浮游动物33科58属80种,其中,原生动物10科13属19种、轮虫10科22属32种、枝角类4科9属13种、桡足类3科8属10种、其他浮游动物6科6属6种。浮游动物密度219.4~2 200.3个/L,年均813.2个/L。其中,原生动物30.0~2 400.0个/L,年均660.7个/L,占81.25%;轮虫3.0~780.0个/L,年均145.4个/L,占17.88%;枝角类0~12.0个/L,年均4.1个/L,占0.50%;桡足类0~13.0个/L,年均2.7个/L,占0.33%;其他0~4.0个/L,年均0.3个/L,占0.04%。种类数的季节分布为春季55种、夏季48种、秋季71种、冬季63种;水平分布全湖以鸟岛区域和靠近草海处种类数最丰富,东部较西部丰富,南部较北部丰富,湖周种类较湖心丰富。密度的季节分布为春季693.2个/L、夏季903.4个/L、秋季933.0个/L、冬季722.9个/L;水平分布北部多于南部,东部和西部差距不大,湖心最深区域明显偏低。区系成分大都是生态幅较大的种类,以广温性种类为主,也有一些南方种和冷水性种类分布;生态型则以浮游型种类较多,底栖-周丛型也有一定数量。浮游动物4个类群的优势种都不十分突出,普通表壳虫(Arcella vulgaris)、独角聚花轮虫(Conochilus unicornis)、曲腿龟甲轮虫(Keratella valga)、针簇多肢轮虫(Polyarthra trigla)、透明溞(Daphnia hyaline)、长额象鼻溞(Bosmina longirostris)、西南荡镖水蚤(Neutrodiaptomus mariadvigae)、短尾近剑水蚤(Tropocyclops prasinus)常见。影响4个类群密度变动的主要水环境因素,原生动物食物条件,轮虫为水深、水温、总碱度和食物条件,枝角类为水温、溶解氧、矿化度和氨氮,桡足类为水温、透明度、氨氮和矿化度。     

明珠湖水体中轮虫的年度变化及多样性分析

为了解上海市崇明县明珠湖内轮虫的数量分布、群落特征、种类组成、优势种、物种多样性及年度变化,在湖内设点采样后镜检计数并进行种类鉴定。调查和分析结果:共鉴定出轮虫46种,隶属于17科21属;轮虫生物密度的年均值为2 065.25 ind/L,生物量年均值为6.177 mg/L,其密度在夏季最高,生物量在春季最高;明珠湖轮虫的Shannon-Wiener多样性指数、丰富度指数和均匀度指数均较低,优势种的优势度指数较大。     

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.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).