鱼类越冬注意些啥？

时下已进入鱼类越冬季节，如何确保鱼类安全越冬，是广大渔农及养殖单位迫在眉睫的一件大事。现就鱼类越冬注意事项介绍如下。科学选池越冬池宜低于地平面，位于背风向阳处。要保证水源充足，注排水便利，水深1．5m以上。温水性鱼类越冬，水质要清新，结冰前溶氧量应在10mg／L以上，冰期溶解氧保持在5mg／L以上．pH值7．5～8．5。池底粘土夯实，平坦，保水性能好。热带鱼越冬．鱼池面积1330～3330m^2，池上建造塑料大棚保温．每667m^2放鱼350～450kg，条件好的池塘也可放养到500kg以上。     

酚类化金物对金鱼的急性毒性试验

在常温静水条件下，用苯酚、二氯酚和对硝基酚对金鱼幼鱼进行急性毒性试验。结果表明：苯酚24hLC50为41．6mg／L，48hLC50为32．3mg／L，安全浓度为5．8mg／L；二氯酚24hLC50为19．5mg／L，48hLC50为12．9mg／L，安全浓度为1．7mg／L；对硝基酚24hLC50为33．2mg／L，48hLC50为16．2mg／L，安全浓度为1．2mg／L。     

亚硝酸盐对长尾墨金丝神仙幼鱼的急性毒性试验

采用静水生物试验测定了NO2^- -N对长尾墨金丝神仙幼鱼（2．541±0．349em）的急性毒性，并探讨了CaCl2和NaCl的解毒效果。结果表明，24h、48h、72h、96h半致死浓度（LC50）分别为164．25mg／L、98．41mg／L、76．73mg／L、48．90mg／L；安全浓度为4．89mtg／L；50mg/L的CaCl2具有较好地减小NO2^- -N毒性的效果。     

乙腈对自然水域的污染及氰化物毒性的消解试验

乙腈为含氰的有机化合物（甲基腈），对水域中鱼类有极强的毒杀作用。2006年对受其污染的安达市富来湖5处水样进行了检测和鱼类存活试验。检测方法是：异烟酸一吡唑啉酮比色法。氰化物浓度分别是：安01#0．018mg／L；安02#0．019mg／L；安03#0．067rag／L；安04#0．042mg／L；安05#0．009mg／L。均超出GB／T7486．1987标准≤0．005mg／L标准量。其中污水放口最高，超标134倍。鱼类在三组水样中情形不同：原水样的A组安05#内，鱼类存活18h。加入渔业用漂白粉的B组鱼反应剧烈，存活时间明显缩短，除B组安05#外均不超过1h。加入渔业用硫酸铜的C组（0．7mg／L），鱼类存活时间均超过12h，最长的C组安05#96h成活100％。     

再谈鱼类安全越冬管理技术

黑龙江省地处北方寒冷地区，封冰期长达150～180天，冰的厚度高达80～100cm，鱼类安全越冬至关重要。2009年由于冬季雪大，2010年春季开冰时间晚，造成鱼类越冬成活率低，全省越冬灾害损失鱼类22115吨，经济损失达2．6亿元。为了提高今年鱼类越冬，下面谈一下加强鱼类安全越冬管理问题。     

两种方法培育的仿刺参幼参(Apostichopus japonicus)越冬期的成活率与生长

2005年11月至2006年4月，将室外土池培育（简称土池苗）和室内工厂化培育的仿刺参（Apostichopus japonicus）幼参（简称工厂苗）放养在室外池塘和蓄水池的网箱中，比较了越冬成活率和生长速度，测定了水质变化。经113d的越冬后，土池苗和工厂苗体重分别增加了79．2％和93．0％；土池苗（92．09％）的成活率比工厂苗（82．18％）高12．3％。蓄水池中的幼参体重增加了110．0％，成活率为10．2％。实验期间，蓄水池和土池中水温分别变化在．2．0℃～10．2℃和1．70℃～6．81℃；溶解氧量变化在2．51mg／L-7．21mg／L和6．75mg／L-15．19mg／L；土池水中溶解氧和氨态氮的含量随水温的“高-低-高”而呈“低-高-低”和“高-低-高”的变化；底栖硅藻的生物量变化在1．20mgim2～1553．56mg／m2之间，优势种为舟形藻（Navfcula sp）和新月拟罄形藻（Nitzschiella closterium）．文中还讨论了海参室外土池或网箱越冬的可行性。     

3种重金属对鲫鱼苗的急性毒性和联合毒性试验

在水温为20±1℃的静水条件下，用Pb^2＋、Cr^6＋、Zn^2＋对鲫鱼苗进行联合毒性试验（离子浓度比1：1）。试验得出Ph^2＋、Cr^6＋联合对鲫表现出协同作用，其24、48、96小时的半致死浓度分别为：46．95、35．42、21．62mg／L；2种安全浓度为6．05、2．16mg／L。Pb^2＋、Zn^2＋联合对鲫表现出拮抗作用，其24、48、96小时的半致死浓度分别为29．69、22．23、19．08mg／L；2种安全浓度为：3．74、1．91mg／L。Cr^6＋、Zn^2＋联合对鲫表现出协同作用，其24、48、96d、时的半致死浓度分别为13．86、11．40、9．99mg／L；2种安全浓度为：2.31、1．00mg／L。     

昆承湖浮游生物调查与生态渔业研究

2002～2003年对昆承湖水中浮游生物进行调查分析，共检测到浮游植物7门52个种属，年平均数量为161．10万个／L，生物量为2．47mg／L；浮游动物4门56个种属，年平均数量为582、36个／L，生物量为3．40mg／L。通过对湖泊鱼类结构调整，恢复水生植物，力求昆承湖渔业朝生态渔业方向发展。     

投喂冰鱼下杂鱼和配合饲料对大口黑鲈养殖水质的影响

为了研究投喂冰鲜下杂鱼与配合饲料对大口黑鲈养殖水质的影响，在室内水泥池进行了一个月的饲养试验。对水体中的COD、PO4^-P、TP、TN、NH3^--N、NH，-N、NO2^--N等指标进行了测定。结果表明，投喂两种饲料各指标均有不同程度的增加，但养殖一个月后冰鲜组比饲料组要高许多；杂鱼组COD、PO4^--P、TP、TN、NH3^--N、NH3-N、NO2^--N分别为25．3mg／L、2．4mg／L、2．28mg／L、3．44mg／L、3．44mg／L、2．91mg／L、0．52mg／L、0．075mg／L，而配合饲料组分别为10．2mg／L、0．58mg／L、0．855mg／L、2．17mg／L、0．29mg／L、0．048mg／L、0．03mg／L。特别是PO4^--P、TP，冰鲜组分别为饲料组的4．2倍和2．7倍。这说明投喂人工饲料可以减轻有机污染程度。特别是在控制PO4^--P、TP的增加方面效果显著。试验结果对于控制水体的富营养化具有重要的指导意义。     

无公害水产养殖基本概念、要求及关键控制技术（二）

第二篇罗非鱼无公害养殖基本的关键控制技术 一、利用生物增氧结合增氧机满足罗非鱼对溶解氧的需求 1、溶氧对罗非鱼的影响 罗非鱼对水中缺氧具有较强的敏感性：通常水中溶氧下降至2mg／L，鱼类则开始出现浮头现象，但它对低氧的适应能力强，其窒息点为0．07～0．28mg／L；当DO〈I．6mg／1时，罗非鱼摄取食量减少，饲料系数比在2．2mg／1时约高一倍。因此，池塘中的溶解氧对罗非鱼非常重要，不能因为罗非鱼不浮头死亡就不开增氧机，开增氧机不光是救命，更重要的是能提高饲料利用率，促进鱼类生长。     

丁香酚对花鲈幼鱼的麻醉效果

为研究丁香酚对花鲈(Lateolabrax maculatus)幼鱼的麻醉效果。采用静水方法在水温(27±1)℃下研究不同质量浓度丁香酚(20、25、30、40、50、60、80 mg/L和100 mg/L)对规格为(21.6±2.75)cm长和(110.3±30.67)g重的花鲈麻醉效果和呼吸频率的影响。25~100 mg/L质量浓度的丁香酚均能使花鲈进入深度麻醉期,且麻醉浓度与平均入麻时间呈负相关,与平均复苏时间成正相关;丁香酚质量浓度为50 mg/L时,麻醉效果较好。低浓度丁香酚20 mg/L对花鲈呼吸频率影响不明显。在质量浓度达到40~100 mg/L时,鱼体由麻醉期(A3)进入深度麻醉期(A4),呼吸频率迅速降低。以50 mg/L丁香酚将花鲈麻醉后再在空气中进行暴露,暴露时间与复苏时间呈正相关。暴露时间在2~30 min范围内的复苏率为100%。当时间增加至35、40和45 min时,复苏率降低至66%,33%和0。且暴露时间大于20 min花鲈只能进入恢复期3期(R3)。因此,50 mg/L的丁香酚麻醉液是花鲈幼鱼的理想麻醉浓度。     

美洲鲥当年鱼种池塘大棚越冬养殖试验

于2017—2019年采用在池塘上方搭建简易保温大棚的方式开展了美洲鲥当年鱼种越冬养殖试验,研究探讨了越冬养殖相关的技术参数。结果显示:搭建保温大棚后,冬季池塘水温可保持在10℃以上,在美洲鲥当年鱼种(0+龄鱼种,平均体长12.45~16.65 cm,平均体质量27.29~66.41 g)放养密度为1518~2970尾/亩(15亩=1 hm^2,下同)和81.04~100.78 kg/亩的条件下,在越冬前中期(12月至次年3月中旬),日投饲量在0.8~1.6 kg/亩,越冬后期(次年3月中旬至4月上中旬),日投饲量也由2.0 kg/亩左右迅速增加到4.0~5.0 kg/亩。经过125~130 d的越冬养殖,鱼种平均体长达17.48~21.19 cm,增长28.04%~40.40%,平均体质量77.57~137.96 g/尾,增加了106.53%~184.24%,鱼种的体长和体质量特定生长率分别为(0.193~0.261)%/d和(0.585~0.804)%/d,日均增长量和日增重分别为0.036~0.039 cm/d和0.387~0.572 g/d;收获时美洲鲥鱼的肥满度为1.42~1.43 g/cm3,养殖成活率为89.29%~94.81%,饲料系数为1.50~1.65,亩产量为198.50~205.68 kg。试验结果表明,在江浙地区,养殖池塘上方搭建保温大棚后,冬季池塘水温(10~20℃)在美洲鲥当年鱼种的适宜水温范围,能获得较理想的越冬养殖效果。     

Minimally invasive evaluation of the anaesthetic efficacy of MS‐222 for ornamental discus fish using skin mucus biomarkers

Skin mucus has been demonstrated to provide stress biomarkers for evaluating the physiological status, providing new convenient and non‐invasive methods to detect stress response in fish. Here, we investigated the anaesthetic efficacy of tricaine methanesulphonate (MS‐222; 75–115 mg/L) for discus Symphysodon aequifasciata (34.27 ± 4.46 g; 8.10 ± 0.59 cm) using skin mucus stress biomarkers. The induction time, recovery time and respiratory frequency were also determined. According to the criteria for anaesthesia and recovery, discus fish to reach stage A3 (deep anaesthesia) within 3 min and to reach stage R4 (full recovery of normal behaviour) within 5 min were observed at 95–105 mg/L MS‐222. Respiratory frequency increased first and then decreased during MS‐222 exposure and increased after recovery. At 10 min after deep anaesthesia, a lower mucus glucose was only observed at 115 mg/L MS‐222. No change in mucus cortisol and increased lactate were observed in all treatments. Increased mucus protein was observed at 75, 85 and 95 mg/L MS‐222. At 10 min after recovery, increased mucus glucose and decreased mucus protein were observed at 85, 95 and 115 mg/L MS‐222, but increased mucus cortisol only at 115 mg/L and lactate only at 75 and 105 mg/L MS‐222. At 24 hr after recovery, mucus glucose returned to the initial level only at 75, 95 and 105 mg/L MS‐222, while cortisol at 75 and 85 mg/L and protein and lactate at 75 mg/L respectively. Overall, the effective dose of MS‐222 for discus fish has been suggested to be 95–105 mg/L.     

枯草芽孢杆菌对海水鱼塘生态因子的影响

为探讨枯草芽孢杆菌(Bacillus subtilis)在鱼类养殖池塘中的生态作用,采用直接往养殖水体中投放该制剂的方法,研究分析微生物数量及其与环境因子的相关关系。结果显示,枯草芽孢杆菌,实验池数量为0.35×10~3~1.45×10~3cfu/m L,对照池为0.04×10~3~0.08×10~3cfu/m L;浮游植物生物量,实验池为0.094~1.521 mg/L,对照池为0.103~0.763 mg/L,实验池中枯草芽孢杆菌数量和浮游植物生物量均高于对照组。试验鱼塘中枯草芽孢杆菌与硅藻数量呈显著正相关,相关系数0.844(P0.05);当溶氧≥6 mg/L时,枯草芽孢杆菌与亚硝酸盐氮含量呈显著负相关,相关系数-0.915(P0.05)。溶氧过低(2 mg/L)时,枯草芽孢杆菌对亚硝酸盐氮、氨氮没有明显的降解作用;溶氧≥6 mg/L时,对亚硝酸盐氮、氨氮的降解作用明显。研究表明,投放适量浓度的枯草芽孢杆菌能有效改善养殖水体状况,对水质起到进一步净化作用。     

秦山核电温排水对鱼类分布的影响

根据2010年5月(春季)、2010年9月(夏季)和2009年12月(冬季)秦山核电海域渔业资源调查资料以及秦山核电站温排水扩散数学模拟结果,通过秦山核电温排水海域鱼类季节密度的时空分布、优势种、优势种对鱼类总数量的贡献,探讨并分析了秦山核电海域温排水对鱼类分布的影响。结果显示,春季、夏季和冬季的尾数密度分别为5.55×10~3 ind/km~2、22.10×10~3 ind/km~2和10.52×10~3 ind/km~2,重量密度分别为33.80 kg/km~2、59.06 kg/km~2和66.46 kg/km~2。秦山核电海域渔业资源数量季节变化的规律与其他海域相反,冬季最高,春夏季较低,主要与冬季温排水海域具有暖池效应,形成部分鱼类滞留在此越冬有关。温排水平面分布对鱼类分布有重要的影响。主要表现在夏季温排水区域鱼类密度低于其他水域,冬季相反,鱼群滞留在温排水热羽区域,因而显示出温排水海域有较高的鱼群密度。温排水对不同适温习性鱼类影响不同,暖温种能够适应一定的低温,例如,刀鲚(Coilia ectenes)可以在温排水水域越冬,而对高温有耐受性的棘头梅童鱼(Collichthys lucidus)夏季在温排水水域成为优势种。鱼类优势种的适温性决定着鱼群的分布特征,冬季最重要的优势种为刀鲚,在尾数上的贡献率高达45.02,由于该种在温排水的热羽区域分布密集,形成温排水水域鱼群密度大于周边水域的现象。由于温排水改变了渔场环境,导致新的越冬场的形成,有可能形成新的渔汛,引起当地渔场属性的改变。     

Secondary Stress Responses in Juvenile Brazilian Flounder,Paralichthys orbignyanus,throughout and after Exposure to Sublethal Levels of Ammonia and Nitrite

This study investigated the secondary stress responses of Paralichthys orbignyanus exposed to ammonia and nitrite and after recovery. Fish were exposed to 0.12, 0.28, and 0.57 mg NH₃‐N/L, or 5.72, 10.43, and 15.27 mg NO₂‐N/L for 10 d followed by the same time length for recovery. Ammonia‐ and nitrite‐free water was used as a control treatment. Blood samples were collected after 1, 5, and 10 d of exposure and after recovery. Fish exposed to ammonia presented lower and higher glucose levels after 10 d of exposure and recovery, respectively. Ammonia induced initial and transient ionic disturbances and metabolic alkalosis. Nitrite exposure caused hyperglycemia, increased plasma K⁺ levels, and respiratory alkalosis, whereas metabolic acidosis was observed after recovery. Increased proportion of monocytes and/or granulocytes and reduced number of lymphocytes were demonstrated in fish exposed to 0.28 mg NH₃‐N/L (Day 1) and 10.43 mg NO₂‐N/L (Day 5) and after recovery in the 0.28 and 0.57 mg NH₃‐N/L treatments. Exposure to ammonia decreased the proportion of granulocytes on Day 5. In conclusion, exposure to concentrations at 0.12 mg NH₃‐N/L and 5.72 mg NO₂‐N/L provoked physiological disorders in Brazilian flounder. Nonetheless, fish exposed to 5.72 mg NO₂‐N/L following a 10‐d recovery period showed complete resumption of homeostasis.     

Albendazole,levamisole and ivermectin are effective against monogeneans of Colossoma macropomum (Pisces: Serrasalmidae)

This study evaluated the efficacy of albendazole, ivermectin, levamisole, mebendazole and praziquantel on monogeneans of Colossoma macropomum, based on in vitro and in vivo assays. In vitro assays indicated that albendazole (500, 100, 1,500 and 2,000 mg/L), ivermectin (200, 250, 300 and 350 mg/L) and levamisole (50, 75, 100 and 125 mg/L) were 100% effective against Anacanthorus spatulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni, while mebendazole (125, 150, 175 and 200 mg/L) and praziquantel (5, 10, 15 and 20 mg/L) were ineffective. Fish mortality in 24 hr therapeutic baths with 500 mg/L of albendazole was 6.6%, but the behaviour of the animals remained unchanged, while 200 mg/L of ivermectin caused lethargy, signs of hypoxia and 100% mortality within 2 hr, and 125 mg/L of levamisole caused no mortality. The efficacy of 500 mg/L of albendazole was 48.6% in the 24 hr baths, while that of 125 mg/L levamisole was 88.2%. Although ivermectin showed in vitro efficacy, the lowest concentration used in baths was highly toxic to fish. Therefore, we recommend the use of 125 mg/L of levamisole to control and treat monogenean infestations on C. macropomum in fish farming.     

Manganese supplementation of a practical, fish meal based diet for Atlantic salmon parr

This experiment was conducted to study whether practical fish meal based feeds for Atlantic salmon, Salmo salar L., require manganese (Mn) supplementation. Three thousand parr of initial weight 4.7 g were randomly distributed into 10 tanks and given a fish meal based diet, either unsupplemented or supplemented with 5, 10, 50 or 100 mg Mn kg^?1 (as MnSO₄*H₂O) for 12 weeks. The basal diet contained 4.8 mg Mn kg^?1. Mn concentration in vertebrae and whole fish responded linearly to supplemented Mn up to a level of 10 mg kg^?1 and then reached a plateau. Dietary Mn supplementation did not affect weight gain, liver Mn concentration, blood haemoglobin concentration or haematocrit. To the practical feed, a supplementary level of 10 mg Mn kg^?1, giving a total Mn concentration of 15 mg kg^?1 diet, was necessary to maintain normal Mn status as determined by Mn level in vertebrae and whole fish. However, taking into account the variable Mn content in fish meal and the uncertainty about availability, we recommend a general supplementation of 15 mg Mn kg^?1.     

Control of dissolved oxygen levels of water in net pens for fish farming by a microscopic bubble generating system

ABSTRACT:   A microscopic bubble generating system (MBGS) has been developed to control dissolved oxygen (DO) levels suitable for fish farming. The MBGS has been tested to confirm its capability in net pens. Water conditions in a fish farm were monitored every two hours from June to October 2004 by setting an online vertical profiling system (OVPS) close to the net pen. DO in the net pen water decreased to physiologically stressful levels for the fish during the night (4.84–5.51 mg/L), while the DO was kept in saturated conditions during the day, due to oxygen supply from phytoplankton. The MBGS was operated from the evening to the morning of the next day for 16 h, to successfully create DO-saturated conditions in the net pen water at night. By using microscopic bubbles during the warm seasons, DO levels in the net pen water could be improved to a level suitable for fish farming. However, the low DO levels (<5.0 mg/L) of the bottom water occasionally extended to the net pen layers, despite the supply of microscopic bubbles to the water. To maintain the DO of the net pen water at levels suitable for fish farming, DO supply to the net pen water and the bottom water needs to be increased, and the organically enriched sediment just below the net pens needs to be treated.