溴氰菊酯在欧洲鳗鲡体内药代动力学研究

在试验水温(25±1)℃时,按100μg·L-1的剂量给欧洲鳗鲡药浴溴氰菊酯36h后,采用气相色谱法测定血浆和肌肉中的药物浓度,研究了溴氰菊酯在欧洲鳗鲡体内的代谢及消除规律.采用DAS自动化药动学分析程序对数据进行分析.结果表明:欧洲鳗鲡血浆和肌肉中溴氰菊酯经时过程均符合一级吸收一室开放模型,血浆中主要药动学参数为:T1/2k为148.296h,Cmax为18.446μg·L-1,Tmax为14.7h.肌肉中主要药动学参数为:T1/2k为386.912h,Cmax为44.291μg·kg-1,Tmax为49.6h.肌肉作为可食性组织,且消除较慢,因此选取肌肉组织作为残留检测的靶组织,以10μg·kg-1为最高残留限量,在本试验条件下,建议休药期不低于9d.     

孔雀石绿及其主要代谢产物在欧洲鳗鲡肌肉中的蓄积及消除规律

为了解孔雀石绿及其有毒代谢产物无色孔雀石绿在鱼体中的蓄积与消除规律,达到对孔雀石绿的禁用监控,本试验对初始体重为(12.42±2.18) g的欧洲鳗鲡进行0.1 mg·L-1 和0.2 mg·L-1 浓度(P1和P2组)孔雀石绿药浴24 h,再转移到清水中养殖120 d,采用高效液相色谱法测定肌肉组织中孔雀石绿及无色孔雀石绿的残留.在药浴过程中,鳗鲡肌肉组织中孔雀石绿平均含量不断升高,P1和P2组分别于药浴12 h和24 h达到最高值(720.5 ±192.6) μg·kg-1和(1404.8±421.9) μg·kg-1;在清水养殖过程中,孔雀石绿在鳗鲡肌肉中含量波动式下降,并于水浴2160 h (90 d)时两个处理组都低于检测限度.肌肉中所含无色孔雀石绿,在药浴过程以及清水养殖的开始一段时间内不断升高,P1和P2组分别于水浴的72 h和120 h达到最高值(960.1±251.0) μg·kg-1和(1 625.8±183.2) μg·kg-1,然后呈波动式下降,至实验结束(水浴120 d)时两个实验组肌肉中还有一定残留.结果表明,无色孔雀石绿的代谢消除时间较长,可以作为检测的标志物.另外,不同浓度的孔雀石绿在鳗鲡肌肉中的代谢规律相似,只是随药浴浓度升高,肌肉中孔雀石绿和无色孔雀石绿含量最高值出现时间有所滞后,以及消除时间相对延长.     

阿维菌素在鲈鱼肌肉组织中的残留与消除规律

为了解实际养殖过程中使用阿维菌素药物后,鲈（Lateolabrax japonicus）对阿维菌素的蓄积及消除规律,以指导阿维菌素药物在实际生产中的应用。以毒性试验为基础,在确定96 h半致死质量浓度（LC50）后,以0.25倍LC50,即指导用药量,质量浓度为4 ng·mL-1,结合实际养殖用药情况,药浴72 h后换水,观察阿维菌素在鲈鱼肌肉组织中的残留与消除规律。文章建立高效液相色谱-串联质谱法测定鲈鱼中阿维菌素残留量的方法,并以此法测定鲈鱼肌肉组织中阿维菌素的质量浓度。结果表明,随着药浴时间的延长,鲈鱼肌肉组织中的阿维菌素质量分数逐步增加,在药浴结束时达到峰值8.767μg·kg-1,随后阿维菌素在体内的残留量随消除试验的进行逐渐下降,至第528小时降至检测限以下。     

氟苯尼考在欧洲鳗鲡体内的药物代谢动力学的研究

应用反相高效液相色谱法对口灌和肌肉注射氟苯尼考在欧洲鳗鲡(Anguilla anguilla)体内的代谢规律进行了研究.按100 mg·kg-1口灌给药后血浆、肌肉、肝脏、肾脏中氟苯尼考浓度的达峰时间分别为2h、6h、0.5h、1h,以后开始缓慢下降,给药2d后血浆、肌肉、肝脏、肾脏中的氟苯尼考浓度分别为4.209μg·mL-1、0.792μg·g-1、0.493μg·g-1、1.448μg·g-1,给药3d后血浆中的氟苯尼考浓度分别为0.0836μg·mL-1,肌肉、肝脏、肾脏中的氟苯尼考浓度均未检出;按100mg·kg-1肌肉注射给药后血浆中氟苯尼考浓度达峰时间为0.5h,以后开始缓慢下降,给药5d后血浆中的氟苯尼考浓度为0.1151μg·mL-1,给药10d后血浆中的氟苯尼考浓度未检出.口灌氟苯尼考在欧洲鳗鲡体内血浆、肌肉、肝脏、肾脏中分布可用开放性二室模型来描述,口灌给药的血浆、肌肉、肝脏、肾脏中的消除半衰期(T1/2β)分别为27.939h、18.844h、11.83h、36.87h;肌肉注射氟苯尼考在欧洲鳗鲡体内血浆、肌肉、肝脏、肾脏中分布可用开放性一室模型来描述,肌肉注射给药的血浆中的消除半衰期(T1/2β)为37.52h.     

药浴给药恩诺沙星及其代谢产物在欧洲鳗鲡体内的药代动力学研究

应用反相高效液相色谱法,研究药浴给药条件下,恩诺沙星及其代谢产物环丙沙星在欧洲鳗鲡体内的药代动力学.按10mg·L-1药浴给药后,恩诺沙星在欧洲鳗体内各组织器官中分布可用开放性二室模型来描述.血浆、肌肉、肝脏和肾脏中恩诺沙星达峰时间分别为44.27h、42.74h、50.69h、95.80h,以后开始缓慢下降,血浆、肌肉、肝脏和肾脏中代谢产物环丙沙星达峰时间分别为48.89h、55.34h、54.64h、100.0h.给药3个月后血浆、肌肉、肝脏和肾脏中的恩诺沙星浓度分别为0.0844μg·mL-1、0.09959μg·g-1、0.01242μg·g-1、3.7164u·g-1;恩诺沙星在血浆、肌肉、肝脏和肾脏中的消除半衰期(T1/2β)分别为908.07h、901.24h、59.32h、767.81h.鉴于恩诺沙星和其代谢产物环丙沙星在欧洲鳗鲡体内消除较慢,建议养成阶段不使用此药.     

阿维菌素在模拟水产养殖生态系统中的蓄积与消除规律

采用UPLC-MS/MS法,研究了阿维菌素泼洒用药后,该药物在水体、底泥、伊乐藻(Elodea nuttallii)和水产动物体内的蓄积与消除规律。结果显示,以6μg/L浓度单次泼洒用药后,水体中阿维菌素消解较快,其半衰期为63.8h。阿维菌素在养殖水环境中消减的同时,逐渐由水体向底泥、伊乐藻和水产动物迁移。底泥中阿维菌素峰浓度、曲线下面积和半衰期分别为1.25μg/kg、469.2μg/(kg·h)和115.5 h,说明伊乐藻中的相应值分别为8.75μg/kg、2521.7μg/(kg·h)和315.0h,说明伊乐藻对阿维菌素有明显的吸收和富集作用。该模拟系统中的异育银鲫(Carassius auratus gibelio)对阿维菌素具有明显的吸收,其血液、肾、鳃、肝和肌肉组织阿维菌素的最高浓度(C_(max))依次为50.9、45.37、21.25、15.47和11.9μg/kg;而该模拟系统中的中华绒鳌蟹(Eriocheir sinensis)仅鳃组织检出阿维菌素,其C_(max)在12h为8.08μg/kg,血淋巴、肌肉和肝胰腺等组织均未检出阿维菌素。生物富集系数F_(BC)值显示,对阿维菌素的富集浓度由高到低依次为鲫鱼、伊乐藻、中华绒鳌蟹、底泥,显示阿维菌素在不同分配相和不同生物组织的富集作用差异较大。     

诺氟沙星在大黄鱼体内的药代动力学及残留研究

在试验水温(22±2)℃时,按10 mg.kg-1的剂量给大黄鱼单次口服诺氟沙星后,用高效液相色谱法测定血浆和组织中的药物浓度,研究了诺氟沙星在大黄鱼体内的代谢及消除。结果表明血药时间数据符合一级吸收二室开放模型,吸收分布迅速,但消除缓慢,半衰期(T1/2 Ka、T1/2α、T1/2β)分别为0.703 0、2.092 6、154.326 5 h,最大血药浓度为0.886 4μg.mL-1,达峰时间为2.091 4 h,药时曲线下面积(AUC)为97.803 8μg.h.mL-1。组织中肝脏的药物浓度最高,在测定的时间里各组织的药物浓度高于血浆。药物消除速度依次为:肾脏、肝脏、肌肉,消除半衰期分别为135.88、173.25、223.55 h,肌肉作为可食性组织,且消除最慢,因此选取肌肉组织作为残留检测的靶组织,以50μg.kg-1为最高残留限量,因此在本试验条件下,建议休药期不低于23 d;在治疗大黄鱼细菌性疾病时,以诺氟沙星10 mg.kg-1剂量给药,一般1 d 1次,连用2~3 d。     

2种水温条件下罗非鱼体内氟苯尼考的药物动力学比较

采用药饵给药，药物剂量为10mg·kg^-1，比较研究了22和28℃水温条件下奥尼罗非鱼（Oreochromis niloticus×O．aureus）体内氟苯尼考的药物动力学。结果得出，22℃组和28℃组罗非鱼血浆的峰药浓度（Cmax）分别为4．46和3．90μg·mL^-1，达峰时间（Tmax）均为12h，消除半衰期（T1/2β）分别为10．03和8．12h，药-时曲线下面积（AUC）分别为86．68和72．44h·μg·mL^-1。相应条件下的肌肉Cmax分别为6．88和4．59μg·g^-1，Tmax均为12h，T1／2β分别为10．97和8．03h，AUC分别为112．71和73．66h·μg·g^-1。低温组罗非鱼血浆和肌肉中药物的T1／2β均长于高温组，前者分别比后者长1．91和2．96h，表明低温组罗非鱼体内药物的消除速度慢于高温组。虽然2个水温组血浆和肌肉中药物的Tmax相同，但低温组血浆、肌肉的Cmax和AUC均明显高于高温组，表明低温组罗非鱼吸收利用药物程度高于高温组。     

室外池塘自然养殖条件下呋喃西林代谢物在中华绒螯蟹体内残留和消除规律

采用高效液相色谱串联质谱(HPLC-ESI/MS/MS)法分析呋喃西林主要代谢物氨基脲(Semicarbazide,SEM)在中华绒螯蟹(Eriocheir sinensis,以下简称河蟹)体内的残留及消除规律。设2个试验组和1个对照组,2个试验组以20 mg·L-1和80 mg·L-1的呋喃西林溶液浸泡河蟹(扣蟹)60 min后,转移至饲养池塘中,并在给药后1 h、2 h、4 h、8 h、12 h、24 h、2 d、4 d、8 d、12 d、16 d、20 d、30 d、40 d、50 d、60 d、80 d、100 d、120 d、150 d进行各组织取样分析。结果显示:在停药2 h时,2个浓度试验组河蟹的肌肉、肝胰腺和鳃中SEM均达到高峰,其中,20 mg·L-1试验组测定值分别为(152±21.7)、(234.0±12.0)、(3 160±169)μg·kg-1,80 mg·L-1试验组测定值分别为(327±31.2)、(372±27.2)、(4 623±247)μg·kg-1。停药2 h后,2个浓度试验组河蟹各组织中SEM均呈现不同的消除速率,其中20 mg·L-1试验组的消除速率分别为0.315μg·(kg·h)~(-1)(肌肉)、0.487μg·(kg·h)~(-1)(肝胰腺)和4.39μg·(kg·h)~(-1)(鳃);80 mg·L-1试验组的消除速率分别为0.454μg·(kg·h)~(-1)(肌肉)、0.516μg·(kg·h)~(-1)(肝胰腺)和6.43μg·(kg·h)~(-1)(鳃)。停药960 h后,2个浓度试验组各组织中SEM残留均低于判定限(1.0μg·kg-1)。     

丁香酚在罗非鱼体内的药物代谢动力学研究

为了解丁香酚在罗非鱼体内的代谢动力学特征,利用高效液相色谱法(HPLC)检测经丁香酚麻醉后苏醒的吉富罗非鱼(Oreochromis niloticus)血浆、肝脏及肌肉中丁香酚的质量浓度变化。试验结果:采用30 mg/L丁香酚药浴后,罗非鱼血浆、肝和肌肉中的药时数据均符合非房室模型;丁香酚在罗非鱼血浆、肝脏和肌肉中的药代动力学参数显示,峰值浓度(Cmax)分别为8 257.52μg/m L、88.62μg/kg和73.78μg/kg,达峰时间(Tmax)分别为0.5、1和2 h,消除半衰期(t1/2)分别为11.267 3、75.616 1和24.147 4 h,药时曲线下面积(AUC0~∞)分别为83 738.054 3 h·μg/m L、1 466.467 7 h·μg/kg和1 131.101 7 h·μg/kg,0~∞平均滞留时间(MRT0~∞)分别为11.498 2、85.284 4和39.388 7 h,表观分布容积(Vz)分别为1.941 2m L/kg、743.903 0 kg/kg和307.994 9 kg/kg。结果表明,丁香酚在罗非鱼体内分布广泛、消除慢、停留时间长。本研究可为罗非鱼活体运输中麻醉剂的安全使用提供参考。     

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).