阿根廷滑柔鱼(Illex argentinus)适宜栖息地模型比较及其在渔场预报中的应用

根据2003–2007年1–5月西南大西洋阿根廷滑柔鱼生产统计数据以及表温(SST)、海面高度(SSH)等海洋遥感数据,以作业次数为基础采用外包络法建立SST、SSH的适应性指数模型。分别采用算术平均法(AMM)和几何平均法(GMM)建立栖息地指数(HSI)模型,并对2003–2007年1–5月的HSI值与实际产量和作业次数作比较。研究结果显示,AMM和GMM均拟合较好,HSI>0.6时,AMM的产量和作业次数比例分别为86.75%和89.82%;GMM的产量和作业次数比例分别为84.30%和85.80%,AMM稍优于GMM。利用2008年1–5月的阿根廷滑柔鱼生产数据进行实证分析,结果显示,作业渔场主要分布在HIS>0.6的海域,其产量占总产量的64%以上,作业次数占总作业次数的68%以上;基于SST和SSH的AMM栖息地指数模型可用于阿根廷滑柔鱼中心渔场的实时动态预报,为该资源的高效开发提供科学依据。     

秋冬季智利竹鱼栖息地指数模型比较

根据2003—2009年5—9月我国大型拖网渔船捕捞智利竹鱼的生产统计数据,结合海表面温度(SST)和海表面高度(SSH)的海洋环境因子,以作业网次和单位捕捞努力量渔获量(CPUE)作为适应性指数(SI),采用外包络法分别建立SST、SSH的SI,采用算术平均法(AMM)、几何平均法(GMM)、基于权重的AMM分别建立栖息地指数(HSI),并用2010—2011年度生产捕捞数据进行比较与验证。结果显示,以作业网次为基础的SI为最适;AMM优于GMM;考虑到权重的AMM优于没有考虑权重的AMM,5—9月最适HSI模型的SST权重分别为0.4、0.7、0.6、0.7、0.1,2010—2011年渔获量和作业网次的验证预报精度分别为75%~93%、80%~90%,可作为秋冬季智利竹鱼栖息地指数模型。研究表明,不同月份的SST和SSH对秋冬季智利竹鱼渔场分布有着不同的影响。秋冬季是智利竹鱼的主要渔汛期,本研究为准确建立其渔场预报模型奠定了基础。     

秋冬季智利竹(竹夹)鱼栖息地指数模型比较

秋冬季是智利竹筴鱼的主要渔汛,准确建立其渔场预报模型具有现实的意义。为了找出适宜的秋冬季智利竹筴鱼栖息地指数模型,论文根据2003-2009年5-9月智利竹筴鱼的商业捕捞数据, 结合海表面温度(SST)和海表面高度(SSH)的海洋环境因子,以作业次数为基础,采用外包络法分别建立SST、SSH 的适应性指数(SI),采用算术平均法(AMM)、几何平均法(GMM)建立栖息地指数(HSI)模型计算其栖息地指数,并以2010-2011年度的捕捞数据进行验证。研究结果表明：以作业次数为基础,采用外包络法建立SST、SSH 的适应性指数为最适,5-9月SST权值分别为0.4、0.7、0.5、0.7、0.1的算术平均法适合秋冬季智利竹筴鱼栖息地指数模型。研究也以为,不同月份的SST和SSH对秋冬季智利竹筴鱼渔场分布有着不同的影响。     

基于最大熵模型分析西南大西洋阿根廷滑柔鱼栖息地分布

根据2008—2010年中国鱿钓船在西南大西洋海域得到的生产数据及海洋环境数据(海表面温度,sea surface temperature,SST;海面高度sea surface height,SSH;叶绿素-a浓度,chlorophyll-a,chl.a),利用最大熵模型(Max Ent)分析捕捞主渔汛期间(1—4月)阿根廷滑柔鱼的潜在栖息地分布,同时与实际作业位置相比较,结合海洋环境因子分析不同年份分布差异的原因。模型运算结果显示:阿根廷滑柔鱼潜在分布区域的变化与实际作业位置变动基本一致;南北方向上,2008年和2009年的潜在分布区域较为广泛,而2010年的潜在分布区域较为狭窄,且主要分布在45°S以南的区域。Jackknife检验表明,SST是影响阿根廷滑柔鱼分布的首要环境因子,SST等温线分布可用来表征海流的强弱进而影响阿根廷滑柔鱼的分布,其中12°C等温线可以作为寻找渔场的一个指标。SSH等高线分布及其涡的变化也会影响到阿根廷滑柔鱼分布。chl.a只能间接地反映阿根廷滑柔鱼渔场的分布,不能很好地作为表征其分布的环境因子。研究表明,分析阿根廷滑柔鱼栖息地分布及其差异原因应主要观察SST和SSH的变化。     

西南大西洋阿根廷滑柔鱼渔场时空变化及其与表温的关系

阿根廷滑柔鱼(Illex argentinus)是西南大西洋重要的经济性头足类,也是中国大陆鱿钓渔业重要的捕捞对象,掌握其渔场时空分布特性及其与海洋环境之间的关系是合理开发、有效管理资源的基础。本文根据2000²010年中国大陆鱿钓渔业在西南大西洋39°2010年中国大陆鱿钓渔业在西南大西洋39°⁵1°S、57°51°S、57°⁶7°W海域的生产统计数据,对西南大西洋阿根廷滑柔鱼中心渔场时空分布及与海洋表层温度(sea surface temperature,SST)的关系进行了研究。结果表明,167°W海域的生产统计数据,对西南大西洋阿根廷滑柔鱼中心渔场时空分布及与海洋表层温度(sea surface temperature,SST)的关系进行了研究。结果表明,1⁵月间,阿根廷滑柔鱼产量及作业次数在纬度方向由南向北逐渐递增,经度方向上由西向东逐渐递增。不同年份间,阿根廷滑柔鱼渔场重心纬度方向上存在显著性差异,而经度方向分布则不存在显著性差异。相关性分析表明,15月间,阿根廷滑柔鱼产量及作业次数在纬度方向由南向北逐渐递增,经度方向上由西向东逐渐递增。不同年份间,阿根廷滑柔鱼渔场重心纬度方向上存在显著性差异,而经度方向分布则不存在显著性差异。相关性分析表明,1⁵月阿根廷滑柔鱼渔场重心纬度、经度的变化与SST之间存在显著相关性,并且渔场重心均随着SST的升高呈现向南和向西移动的趋势。     

不同时空尺度下近海日本鲭栖息地模型比较

根据2003—2011年7—9月近海日本鲭生产数据，结合海洋遥感获取的海表温度(SST)和海面高度数据(SSH)，利用作业网次与SST和SSH的关系建立适应性指数(SI)模型，将时间和空间尺度分别划分为3个级别，建立9个不同时空尺度下的栖息地适应性指数(HSI)模型，分析比较得出不同时空尺度下近海日本鲭栖息地适应性指数最优模型，并对最优模型进行验证。结果显示，时间尺度为月，空间尺度为1°×1°是建立近海日本鲭栖息地适应性指数模型的最适时空尺度，当HSI大于0.6时，作业网次比重为75.42%，当HSI小于0.4时，作业网次比重为12.93%。利用2012年7—9月生产数据对最优模型进行验证，结果显示，当HSI大于0.6时，作业网次比重为60.89%，当HSI小于0.4时，作业网次比重为13.88%。研究表明，在建立鱼类栖息地适应性指数模型时，需要考虑海洋环境因子的时空尺度，以便更好地预测中心渔场。     

西北太平洋柔鱼栖息地适宜性变动研究

柔鱼(Ommastrephes bartramii)是西北太平洋重要的经济头足类,其栖息地受到气候变化的显著影响。根据中国鱿钓渔船在38°～45°N、140°～160°E作业渔场内的生产数据以及卫星遥感数据,利用信息增益技术选取关键环境因子,以单位捕捞努力量渔获量(CPUE)作为适应性指数,使用算术平均法(AM)和联乘法(GM)分别建立综合栖息地指数模型,对比异常环境条件下(厄尔尼诺和拉尼娜事件)柔鱼栖息地适宜性变动情况。结果表明,1998年La Ni■a事件发生时,西北太平洋传统作业渔场温度升高,海表温度(SST)相对正常年份2008年平均上升2. 72℃;而2009年El Ni■o事件发生时,SST相对正常年份降低0. 45℃。栖息地综合指数模型结果表明,1998年作业比重主要分布于在栖息地指数(HSI)大于0. 8的范围内,作业比重达到80%;2008年作业比重主要分布在HSI值0. 6～0. 8和0. 8～1. 0之间,所占比重在30%～50%左右; 2009年作业比重主要分布在HSI值0. 4～0. 6、0. 6～0. 8和0. 8～1. 0之间,作业比重平均约为32%。此外HSI值低于0. 2的区间面积随着La Ni■a事件、正常年份和El Ni■o事件递增,而HSI值大于0. 4的区间面积随着La Ni■a事件、正常年份和El Ni■o事件递减。研究认为,1998年La Ni■a事件发生时西北太平洋海域柔鱼适宜栖息地面积增加,而2009年El Ni■o事件发生时柔鱼栖息地适宜性变差,导致柔鱼产量变低。     

海表温度变化时近海日本鲭栖息地时空分布预测

海表水温变化影响着中上层鱼类栖息地分布。本研究根据2003—2012年7—12月的近海日本鲭生产统计数据,结合海表温度(SST)数据,利用正态函数分布的方法,分别以作业次数和单位捕捞努力量渔获量(CPUE)为指标建立基于水温的适应性指数(SI),取二者平均值作为栖息地适应性指数(HSI)。在气候变化背景下,假设SST上升或下降0.5、1、2°C时,对各月近海日本鲭最适宜栖息地(HSI0.8)空间和面积变化情况进行预测。结果显示,SST上升时,近海日本鲭适宜栖息地有明显的北移现象,7—12月最适栖息地面积增减比重为–73.1%～44.7%;SST下降时,有明显的南移现象,7—12月最适宜栖息地面积增减比重为–54.9%～123.4%。该研究结果可用于在SST上升等气候变化背景下,以及近海海况发生变化等情况下,对日本鲭栖息地和作业渔场时空分布进行预测。     

基于栖息地指数的东太平洋长鳍金枪鱼渔场分析

长鳍金枪鱼(Thunnus alalunga)是东太平洋海域重要的金枪鱼种类之一,也是我国金枪鱼延绳钓的主要捕捞对象之一。本文根据2009~2011年美洲间热带金枪鱼委员会(IATTC)在东太平洋海域(20°N~30°S、85°W~150°W)长鳍金枪鱼延绳钓生产统计数据,结合海洋遥感获得的表温(SST)和海面高度(SSH)的数据,运用一元非线性回归方法,以渔获产量、单位捕捞努力量CPUE为适应性指数,按季度分别建立了基于SST和SSH的长鳍金枪鱼栖息地适应性指数,采用算术平均法获得基于SST和SSH环境因子的栖息地指数综合模型,并用2012年各月实际作业渔场进行验证。研究结果显示,在东太平洋长鳍金枪鱼的栖息地预测中,以CPUE为适应性指数的栖息地指数模型比以渔获量为适应性指数的栖息地指数模型预测更为准确。2012年中心渔场的预报准确性达75%以上,具较高预报准确度,可为金枪鱼延绳钓渔船寻找中心渔场提供指导。     

不同气候模态下秘鲁外海茎柔鱼栖息地的季节性分布

茎柔鱼（Dosidicus gigas）为环境敏感型头足类，气候的多元变化促使茎柔鱼栖息地发生变动。本研究利用海表温度（SST）和海表面高度（SSHA）两个关键环境因子构建栖息地适宜性指数（HSI）模型，结合太平洋年代际涛动（PDO）指数，分析1950-2015年不同气候模态下秘鲁外海茎柔鱼栖息地的季节性分布规律。结果发现，PDO冷期茎柔鱼栖息地适宜性较高；而PDO暖期栖息地适宜性较低。相较于PDO冷期，PDO暖期下茎柔鱼适宜栖息地分布向东南移动。适宜栖息地的分布位置与适宜的SST和SSHA的重叠区域重合，表明两个关键环境因子与栖息地分布显著相关。此外，适宜栖息地指数距平值与PDO指数的年际变化呈显著负相关关系。春季茎柔鱼渔场栖息地适宜性高于冬季，且冬季适宜栖息地的分布相较春季偏东南方向。茎柔鱼渔场6-11月适宜的SST和最适宜的SST在经度和纬度上的分布存在显著差异，春季（9-11月）最适宜的SST分布逐月向西北方向移动；冬季（6-8月）最适宜的SST分布逐月向东南方向移动。推测不同气候模态下茎柔鱼栖息地季节性分布差异，可能是由于最适宜的SST显著的月间分布差异所致。研究表明，不同PDO时期下茎柔鱼栖息地适宜性具有显著季节性差异，其差异可由环境因子的月间变动来解释。     

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).