长江口及其邻近水域春季虻鲉的食性

采用碳氮稳定同位素技术和聚类分析法对春季长江口及其邻近海域虻鲉(Erisphex potti)的饵料组成、摄食随体长的变化进行研究,结果表明:(1)虻鲉的食物由大于900 μm的浮游动物、细螯虾(Leptochela gracilis)、太平洋褶柔鱼 (Todarodes pacificus)、双喙耳乌贼 (Sepiola birostrata)、火枪乌贼(Loligo beka)、日本枪乌贼(Loligo japonica)、脊腹褐虾(Crangon affinis)和仔稚鱼组成,优势饵料为浮游动物,其重量贡献率为69%～75%.(2)虻鲉的食物组成及摄食量在体长为60 mm时发生较大变化,脊腹褐虾、仔稚鱼及软体动物等饵料对体长大于60 mm的虻鲉的贡献率增大,增幅为1%～12%.     

浙江南部近海两种石首鱼科鱼类的摄食习性及其食性重叠

对 2020 年 8 月、11 月和 2021 年 1 月在浙江南部近海进行的底拖网调查采集的 287 尾白姑鱼(Pennahia argentata)和 204 尾黑姑鱼(Atrobucca nibe)胃含物样品进行分析, 采用聚类分析等统计方法研究了这两种石首鱼科鱼类(Sciaenidae)的食物组成、摄食习性随体长变化及饵料重叠情况。结果表明, 浙江南部近海白姑鱼摄食饵料生物 48 种, 主要摄食桡足类(Copepoda), 以哲水蚤(Calanus)居多。黑姑鱼摄食饵料生物 43 种, 主要摄食鱼类(Pisces) 和虾类(Decapoda), 优势饵料种类为七星底灯鱼(Benthosema pterotum)。随着体长的增加, 两种石首鱼摄食的主要饵料生物均由浮游动物等小型饵料生物转向鱼类和虾类等大型饵料生物, 摄食强度也随之变化, 白姑鱼的摄食强度随着体长增加而逐渐降低, 而黑姑鱼的摄食强度随着体长增加呈先下降后上升的趋势。两种石首鱼的营养生态位宽度存在较大差异, 其中黑姑鱼的营养生态位宽度(3.06)高于白姑鱼(1.82), 二者间的整体饵料重叠系数为 0.22, 但在部分体长组中存在较大的饵料重叠, 这表明浙江南部近海白姑鱼与黑姑鱼在部分生长阶段有发生食物竞争的可能。     

舟山渔场鮸的摄食习性

为了研究鮸(Miichthys miiuy)在舟山渔场生态系统食物网结构中的地位和作用, 本研究于 2021 年 8 月至 2023 年 6 月在舟山渔场逐月采集鮸样品共计 727 尾, 结合胃含物分析法和碳、氮稳定同位素技术, 分析鮸的摄食习性。 结果表明, 舟山渔场鮸的主要饵料生物类群有鱼类(Pisces)、虾类(Decapoda)、口足类(Stomatopoda)、头足类 (Cephalopoda)、双壳类(Lamellibranchia)、蟹类(Brachyura), 优势饵料种为龙头鱼(Harpodon nehereus)、棘头梅童鱼 (Collichthys lucidus)、凤鲚(Coilia mystus)、黄鲫(Setipinna taty)和六丝钝尾虾虎鱼(Amblychaeturichthys hexanema)。 其 δ¹³C 值范围为−19.09‰~−13.04‰, 平均值为(−16.74±1.03)‰, 与体长呈显著负相关(P＜0.01); δ¹⁵N 值范围为 10.72‰~ 15.96‰, 平均值为(12.44±1.36)‰, 与体长呈显著正相关(P＜0.01)。根据 δ¹⁵N 值计算出舟山渔场鮸的营养级范围为 3.93~4.92, 平均营养级为 4.30±0.39, 营养级与其体长呈显著正相关(P＜0.01)。稳定同位素分析结果显示, 口足类对鮸的营养贡献率最高(20.6%), 其次是头足类(18.3%)、虾类(16.4%), 双壳类的食源贡献率最低, 为 13.7%。 鮸全年均摄食, 摄食强度随季节、体长变化显著, 从不同季节来看, 冬季的胃饱满指数最高, 秋季最低; 从不同体长来看, 大个体胃饱满指数低, 小个体胃饱满指数高。空胃率则为秋季最高, 冬季最低; 空胃率随体长变化不明显。 本研究有助于深入了解舟山渔场鮸的摄食习性, 为研究食物网动态变化和营养动力学提供基础资料和科学依据。     

新疆克孜勒河5种土著鱼食性分析

为探究克孜勒河 5 种土著鱼食物组成及其营养级, 本研究选取采自于克孜勒河的塔里木裂腹鱼(Schizothorax biddulphi)、宽口裂腹鱼(Schizothorax eurystomus)、厚唇裂腹鱼(Schizothorax irregularis)、叶尔羌高原鳅(Triplophysa yarkandensis)和长身高原鳅(Triplophysa tenuis) 5 种鱼样品共 46 尾作为研究对象, 运用传统形态学方法, 对样品 5 个摄食器官形态性状进行分析, 通过高通量测序技术分析其肠道食物组成, 并测定了碳、氮稳定同位素以分析其营养级。研究结果显示, 3 种裂腹鱼属鱼类摄食器官形态较为相近, 2 种高原鳅摄食器官形态基本一致; 厚唇裂腹鱼肠长比约为 2.95, 主要食物来源于初级生产者, 包括刚毛柽柳(Tamarix hispida)、野大豆(Glycine soja)和白刺(Nitraria tangutorum)等; 宽口裂腹鱼肠长比较短, 约为 2.56, 食物以初级生产者为主, 如二穗短柄草(Brachypodium distachyon), 也会捕食一些小型鱼类; 塔里木裂腹鱼肠长比较短, 约为 2.38, 食物以裂腹鱼属鱼类为主, 其次为白柠檬(Citrus latifolia); 叶尔羌高原鳅与长身高原鳅比肠长均小于 1, 肠道中裂腹鱼属鱼类丰度达到 95%以上; 塔里木裂腹鱼、宽口裂腹鱼和厚唇裂腹鱼营养级分别为 3.19、2.78 和 2.52, 叶尔羌高原鳅与长身高原鳅营养级为 3.44 和 3.55; 综合判断厚唇裂腹鱼属植食性鱼类, 宽口裂腹鱼为杂食性偏植食性鱼类, 塔里木裂腹鱼为杂食性偏肉食性鱼类, 叶尔羌高原鳅和长身高原鳅为肉食性鱼类。本研究拓展了对克孜勒河食物网的认识, 探明克孜勒河鱼类食物关系和营养级, 为克孜勒河鱼类资源保护及合理利用提供基础数据。     

黄海南部、东海北部小黄鱼饵料组成和摄食强度的变化

根据2001~2004年收集的黄海南部、东海北部的小黄鱼样品,应用研究鱼类摄食习性的常用方法,对小黄鱼的饵料组成和摄食强度的变化进行了研究。结果表明,小黄鱼摄食的饵料种类多达24种,鱼类和甲壳类是其主要的饵料类群,两者在食物中所占的重量百分比之和为93.7%。小黄鱼在不同生活时期的饵料种类和摄食强度变化较大。越冬期的摄食强度最低,为弱摄食期,3月以脊腹褐虾和七星底灯鱼为主;产卵期的摄食强度较高,为中强摄食期,产卵盛期的4月以长额刺糠虾和脊腹褐虾为主,产卵后期的5月以中华假磷虾、鰕虎鱼科和细长脚虫戎为主;索饵期的摄食强度较高,为强摄食期,6月以四盘耳乌贼、长蛸幼体、尖牙鲈和脊腹褐虾为主,7月以蓝圆鲹和虾蛄为主,10月以细条天竺鲷和带鱼幼鱼为主,11月以七星底灯鱼为主,12月以七星底灯鱼和鹰爪虾为主。与20世纪60年代初研究结果比较发现,小黄鱼食物组成发生很大的变化,由以往的浮游动物为主演变为目前的游泳动物为主;产卵时和刚产卵完的群体的摄食需求强烈,较以往的产卵群体停止摄食或少量摄食存在很大差异。     

东海中北部小眼绿鳍鱼食性的季节变化

根据2008年5月~2009年2月收集到的小眼绿鳍鱼胃含物样品,对其摄食习性的季节变化进行了研究。结果表明,小眼绿鳍鱼全年摄食的饵料种类数共有93种,磷虾类、长尾类和鱼类为其主要饵料类群。其食物组成存在季节差异,春季小眼绿鳍鱼以太平洋磷虾、脊腹褐虾和鳀鱼为主要食物;夏季以细巧仿对虾、脊腹褐虾、口虾姑和葛氏长臂虾为主要食物;秋季以太平洋磷虾、戴氏赤虾、细螯虾和鳀鱼为主要食物;冬季以鳀鱼、细螯虾、褐菖鲉和对虾为主要食物。摄食强度的季节变化呈显著差异(P0.05),春季最高,夏季最低;各个季节的主要饵料类群组成存在差异,但长尾类和鱼类在四个季节都有分布。通过与历史资料进行比较发现,东海小眼绿鳍鱼的食物组成与饵料生物的季节变化息息相关。     

东海中北部小眼绿鳍鱼的食物组成及摄食习性的体长变化

应用聚类分析和单因素方差分析等方法.对2008年5月至2009年2月东海中北部小眼绿鳍鱼(Chelidonichthys spinosus)的食物组成及摄食习性的体长变化进行了研究.结果表明.小眼绿鳍鱼摄食的饵料种类有93种.优势饵料种类有太平洋磷虾(Euphausia pacifica)、细巧仿对虾(Parapenaeopsis tenella)、脊腹褐虾(Crangonafnis)和六丝矛尾虾虎鱼(Chaeturichths hexanema).摄食强度有明显的体长变化.同时主要饵料类群组成也有明显的体长差异.鱼类饵料的质量百分比随着体长的增大而增大.尤其当体长大于200 mm后.鱼类成为最重要的饵料类群.而糠虾类的比例则减少.另外.平均单个饵料的质量则随着体长的增大而增大.这符合"最佳摄食理论".聚类分析的结果表明.小眼绿鳍鱼在体长达到100 mm时.摄食范围由狭食性逐步向广食性转变.可以认为小眼绿鳍鱼食性的转变与其体长密切相关.     

北黄海细纹狮子鱼摄食生态的初步研究

根据2007年秋季在北黄海进行的定点底拖网调查,对细纹狮子鱼(Liparis tanakae)的摄食生态进行了初步研究。北黄海的细纹狮子鱼在秋季主要以虾类和底层鱼类为食,属于底栖动物食性鱼类,其优势饵料生物是脊腹褐虾(Crangon affinis)。在调查海域最北部的1号站位,细纹狮子鱼还摄食了较多的大泷六线鱼(Hexagrammos otakii)鱼卵。典范对应分析(CCA)表明,水深、经度、纬度和体长对细纹狮子鱼的食物组成有显著影响(P0.05),而性别和性腺成熟度则没有显著影响(P0.05)。脊腹褐虾体长与细纹狮子鱼体长之间呈显著的正相关(r=0.326,P0.05),而中华安乐虾(Eualus sinensis)体长与细纹狮子鱼体长之间没有显著的相关关系(r=0.219,P0.05);脊腹褐虾(r=-0.372,P0.01)和中华安乐虾(r=-0.799,P0.01)体长与细纹狮子鱼体长的比率与细纹狮子鱼体长之间均呈极显著的负相关关系。细纹狮子鱼的胃总质量和空胃质量均随着体长的增加呈指数增长。     

枸杞岛海藻场褐菖鲉的摄食习性

2007年8月至2008年6月对枸杞岛海藻场生态系统4个盛衰阶段展开调查,共获得297个褐菖鲉样本,对其胃含物进行分析，以研究褐菖鲉摄食习性及其随藻场盛衰、体长的变化规律。结果表明，褐菖鲉的摄食强度很低，空胃率和平均饱满指数随藻场盛衰有显著变化(P<0.05)，空胃率随体长的变化不显著(P>0.05)，平均饱满指数在小于100.0 mm各体长组间无显著差异(P>0.05)；褐菖鲉是底栖生物食性鱼类，食物种类有端足类、虾类、蟹类、棘皮类、多毛类等12大类29种生物，端足类是（%IRI为97.03%）是褐菖鲉最重要的摄食种类；褐菖鲉食物种类随藻场盛衰而变化，在海藻场增长期和茂盛期两个阶段主要摄食虾类和蟹类，在海藻场持续期和衰减期主要摄食端足类；食物种类随体长变化，体长<80.0 mm的褐菖鲉主要摄食端足类等，体长在80.0~99.9 mm的褐菖鲉主要摄食虾类和蟹类，体长大于100.0 mm的褐菖鲉主要摄食鱼类和端足类。     

珠江下游7种典型鲤科鱼类摄食器官形态特征比较

为探究鲤科鱼类的摄食器官形态差异, 以珠江下游的海南鲌(Culter recurviceps)、鲤(Cyprinus carpio)、广东鲂(Megalobrama terminalis)、赤眼鳟(Squaliobarbus curriculus)、草鱼(Ctenopharyngodon idellus)、鲮(Cirrhinus molitorella)和鲢(Hypophthalmichthys molitrix) 7 种典型鲤科鱼类为研究对象, 基于形态解剖和多元分析等方法, 比较了这 7 种鱼类外部和内部摄食器官形态的特征差异。结果显示, 7 种鲤科鱼类外部摄食器官形态的种间差异主要体现在口裂宽、口裂高等与食物捕获有关的性状上, 内部摄食器官形态的种间差异主要体现在咽骨长、咽骨后肢长等与食物咀嚼有关的性状上, 内部摄食器官形态分化程度显著大于外部摄食器官。另外, 研究发现食性对鲤科鱼类内部摄食器官形态影响大于系统发育地位的影响, 外部摄食器官形态性状对于鱼类分类具有重要的参考价值。 本研究揭示了同域分布鲤科鱼类的摄食器官结构差异, 探讨了摄食器官形态结构与食性、系统演化地位的关系, 对于了解鲤科鱼类生态适应机制以及开展珠江鱼类资源保护具有重要意义。     

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.     

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.     

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.     

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).