大口黑鲈“优鲈1号”选育群体肌肉营养成分和品质评价

对大口黑鲈[Micropterus salmoides(Lacépède)]"优鲈1号"(以下简称"优鲈1号")与非选育群体(简称对照组)的肌肉营养成分及营养品质进行分析比较。结果表明,"优鲈1号"和对照组肌肉中水分、粗蛋白、粗脂肪、粗灰分含量分别为73.63%和74.35%、19.34%和19.42%、4.45%和4.67%、1.09%和1.12%,统计分析表明,"优鲈1号"肌肉中水分和粗脂肪含量低于对照组,粗蛋白和粗灰分含量与对照组差异不显著(P>0.05)。对6种矿物质元素进行检测,"优鲈1号"和对照组肌肉中钙(Ca)、镁(Mg)、铁(Fe)、锌(Zn)和硒(Se)含量分别为428.34 mg/kg和424.57 mg/kg、252.63 mg/kg和259.77 mg/kg、6.92 mg/kg和5.76 mg/kg、7.73 mg/kg和5.77 mg/kg、0.40 mg/kg和0.41 mg/kg,统计分析显示"优鲈1号"肌肉中铁(Fe)和锌(Zn)含量显著高于对照组(P<0.05),其他元素差异均不显著(P>0.05)。"优鲈1号"和对照组肌肉中均测定出17种氨基酸,其总氨基酸(TAA)、必需氨基酸(EAA)和鲜味氨基酸(DAA)含量分别为18.10 mg/100 g和17.17 mg/100 g、9.46 mg/100 g和8.72 mg/100 g、8.00 mg/100 g和7.80 mg/100 g,统计分析显示差异均不显著(P>0.05)。根据氨基酸评分(AAS)和化学评分(CS)计算结果,第一限制性氨基酸均为蛋氨酸+胱氨酸(Met+Cys)。"优鲈1号"和对照组肌肉中均检测到28种脂肪酸,其中饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)、多不饱和脂肪酸(PUFA)分别为13.96 g/kg和14.68 g/kg、13.66 g/kg和14.72 g/kg、16.37 g/kg和16.58 g/kg,其中饱和脂肪酸/不饱和脂肪酸(SFA/UFA)均为0.47。综上所述,"优鲈1号"仅在水分、粗脂肪、铁(Fe)和锌(Zn)含量上略优于对照组,其他肌肉营养成分和含量差异均不显著(P>0.05)。     

维生素E对虎龙杂交斑生长、抗氧化及免疫功能的影响

为研究虎龙杂交斑对维生素E(V_E)的最适需求量，评估V_E对虎龙杂交斑生长性能、抗氧化和免疫功能的影响，实验设计了6组VE含量分别为4.1、26.3、40.7、57.1、116.8、209.6 mg/kg的等能(340 kcal/100 g干物质)、等蛋白(占饲料干重的51.5%)、等脂(占饲料干重的9%)的实验饲料，每组3个平行。实验鱼初始均重为(14.22±0.01) g，养殖实验期间每日饱食投喂2次(8:00和16:30)，周期为8周。生长实验结束后每组随机挑选7尾实验鱼进行72 h铜胁迫实验。实验结果显示，摄食57.1 mg/kg VE饲料实验鱼增重率(WG)显著高于摄食4.1 mg/kg VE饲料实验鱼，各实验组肥满度(CF)、肝体比(HSI)和肠系膜脂肪比(IPF)无显著差异。全鱼和肌肉水分、粗蛋白和粗脂肪含量在各V_E处理组之间也无显著差异。摄食209.6 mg/kg VE饲料实验鱼肝脏VE含量高于摄食4.1 mg/kg VE饲料实验鱼。肝脏总抗氧化能力(T-AOC)、血清溶菌酶(LZM)活性和免疫球蛋白(Ig...     

烟酸对杂交鲟幼鱼生长性能、肌肉品质和抗氧化功能的影响

为评价饲料中添加不同水平的烟酸对杂交鲟(Acipenser schrenckii♂×A. baeri♀)幼鱼生长性能、肌肉成分、肌肉质构和抗氧化性能的影响,在基础饲料中分别添加0 mg/kg、30 mg/kg、120 mg/kg、1200 mg/kg的烟酸配制成4种实验饲料,投喂初始体重(54.41±0.79)g的杂交鲟幼鱼84d,实验分为4组,每组3个重复,每个重复15尾鱼。结果表明:饲料添加不同水平的烟酸对杂鲟幼鱼增重率有显著影响(P0.05), 0 mg/kg组增重率显著低于30 mg/kg、120 mg/kg、1200 mg/kg烟酸组(P0.05),各添加组之间无显著差异(P0.05)。各组成活率、饲料系数和肝体比不受饲料烟酸的影响(P0.05)。120 mg/kg烟酸组的肥满度显著低于0 mg/kg、30 mg/kg、1200 mg/kg烟酸组, 0 mg/kg、30mg/kg、1200mg/kg烟酸组之间肥满度无显著差异(P0.05)。120mg/kg烟酸组的脏体比显著低于0mg/kg和1200 mg/kg烟酸组(P0.05),与30 mg/kg烟酸之间无显著差异(P0.05)。肌肉硬度和弹性随烟酸添加水平呈现先增加后降低的趋势, 1200 mg/kg烟酸组的肌肉硬度和弹性显著低于其余各烟酸添加组(P0.05)。30 mg/kg烟酸组的肌肉咀嚼性、回复性和黏性均在各组之间最大,且显著高于0 mg/kg、120 mg/kg、1200 mg/kg烟酸组(P0.05)。30 mg/kg烟酸组的肌肉凝聚性显著高于0 mg/kg、120 mg/kg、1200 mg/kg烟酸组(P0.05), 0 mg/kg、120 mg/kg、1200 mg/kg烟酸组之间无显著差异(P0.05)。肌肉水分、粗蛋白、粗脂肪和灰分含量不受饲料烟酸影响(P0.05)。30 mg/kg烟酸组肌肉T-SOD活力显著高于0 mg/kg和120 mg/kg烟酸组(P0.05),与1200 mg/kg烟酸组无显著差异(P0.05)。30 mg/kg烟酸组肌肉T-AOC活力显著高于0 mg/kg、120 mg/kg、1200 mg/kg烟酸组(P0.05), 0 mg/kg、120 mg/kg、1200 mg/kg烟酸组之间无显著差异(P0.05)。综上所述,饲料中添加烟酸对杂交鲟幼鱼的生长、肉质和抗氧化性能均有一定的改善作用,鲟鱼饲料中烟酸的建议添加量为30 mg/kg。     

草鱼幼鱼肌醇营养需要量的研究

以酪蛋白、明胶和鱼粉为蛋白源,配制含肌醇水平分别为0、50 mg/kg、100 mg/kg、200 mg/kg、400 mg/kg8、00 mg/kg、1 600 mg/kg的7组实验饲料。每组设3个重复,连续投喂体质量(4.78±0.18)g的草鱼(Ctenopharyngodon idella)幼鱼9周,通过测定生长指标、部分血清生化指标和全鱼营养成分来评价饲料肌醇添加水平对草鱼幼鱼的影响。结果表明,饲料中肌醇添加水平≥200 mg/kg使草鱼幼鱼增重率(WGR)、特定生长率、血清中总胆固醇(TC)和低密度脂蛋白胆固醇(LDL-C)含量与对照组相比有显著提高(P<0.05),而血清甘油三酯(TG)含量比对照组有显著降低(P<0.05);200 mg/kg和400 mg/kg肌醇添加组草鱼幼鱼饲料系数(FCR)比对照组有显著降低(P<0.05);饲料中添加肌醇对草鱼幼鱼存活率、血清中高密度脂蛋白胆固醇和全鱼营养成分无显著影响(P>0.05)。对WGR、FCR、TC、TG和LDL-C进行折线回归分析得出饲料中肌醇添加水平为166～214 mg/kg对草鱼幼鱼的生长比较适宜。     

饲料中不同维生素E添加量对黄颡鱼幼鱼生长性能及免疫功能的影响

本研究探讨了饲料中不同维生素E添加量对黄颡鱼(Pelteobagrus fulvidraco)幼鱼生长和免疫的影响。在以鱼粉、豆粕为蛋白源的基础饲料中分别添加0mg/kg(对照组)、25mg/kg、75mg/kg、125mg/kg和175mg/kg的维生素E配成5种实验饲料。在水温(24.0±3.0)℃下,用上述实验饲料分别饲喂平均体质量约为5.1g的黄颡鱼幼鱼50d。实验结果表明,饲料中维生素E的添加量对黄颡鱼的特定生长率和饲料效率的影响不显著(P0.05);而添加量为175mg/kg时,黄颡鱼摄食率显著降低(P0.05);随着饲料中维生素E添加量的增高,黄颡鱼血浆超氧化物歧化酶(SOD)的活性未产生显著变化(P0.05);添加量为125mg/kg和175mg/kg时,血浆中丙二醛(MDA)的含量显著降低(P0.05);白细胞吞噬指数随添加量升高显著上升(P0.05),而吞噬百分率没有显著变化(P0.05)。综合以上结果,饲料中添加适量的维生素E可适当改善黄颡鱼的摄食,增强黄颡鱼的非特异性免疫力和抗氧化能力,从而提高动物的健康状况。推荐在黄颡鱼幼鱼饲料中添加125mg/kg的维生素E。     

许氏平鲉幼鱼对饲料中维生素B6需求量的研究

本实验旨在研究饲料中维生素B6含量对许氏平鲉(Sebastes schlegeli)幼鱼生长、体成分、肝脏酶活和转氨酶基因表达的影响,以确定其对维生素B6的需求量。配制6组维生素B6实际含量分别为2.08(对照组)、3.25、4.16、6.32、10.17和31.14 mg/kg的实验饲料,饲喂初始体重为(36.35± 0.06) g的许氏平鲉幼鱼63 d。结果显示,随着维生素B6含量的增加,实验鱼的增重率(WGR)和特定生长率(SGR)均呈先升高后降低的趋势,4.16 mg/kg组达到最高。4.16 mg/kg组脏体比(VSI)显著高于对照组(P<0.05),3.25?10.17 mg/kg组的肝体比(HSI)和肠体比(ISI)显著高于对照组(P<0.05)。3.25?31.14 mg/kg组的肌肉水分含量显著低于对照组(P<0.05),全鱼和肌肉的粗蛋白和粗脂肪均呈先升后降的趋势。肝脏超氧化物歧化酶(SOD)活力先升高后降低,4.16?10.17 mg/kg组显著高于对照组(P<0.05);丙二醛含量(MDA)先降低后升高,3.25?31.14 mg/kg组显著低于对照组(P<0.05);肝脏维生素B6含量先升高后平稳;3.25?31.14 mg/kg组谷草转氨酶(GOT)和谷丙转氨酶(GPT)活力显著高于对照组(P<0.05)。谷草转氨酶(GOT1和GOT2)基因相对表达量先升后降,3.25?31.14 mg/kg组显著高于对照组(P<0.05);谷丙转氨酶(GPT1和GPT2)基因相对表达量先升后降,均在6.32 mg/kg组达到最大值;酪氨酸转氨酶(TAT)基因相对表达量先升后降,4.16?10.17 mg/kg组显著高于其他组(P<0.05);丝氨酸转氨酶(SerC)基因相对表达量呈下降趋势,4.16?31.14 mg/kg组显著低于对照组和3.25 mg/kg组(P<0.05)。以WGR、肝脏维生素B6含量和GPT为评价指标,经折线回归分析表明,体重36 g的许氏平鲉幼鱼维生素B6的需求量为3.53?6.32 mg/kg饲料。     

高水平烟酸对吉富罗非鱼脂代谢和体脂沉积的影响

为探讨高水平烟酸对鱼类脂代谢和体脂沉积的影响,本研究以吉富罗非鱼(Oreochromisniluticus)为研究对象,设计了2个实验。在实验I中,为确定烟酸是否具有改善血脂作用及其适宜水平,首先通过高糖高脂饲料喂养初始体重(15.28±0.23) g的实验鱼40 d,建立高血脂模型,随后改投添加500 mg/kg、1000 mg/kg、2000 mg/kg烟酸的饲料。结果发现添加500～2000mg/kg的烟酸,均有降低实验鱼血清胆固醇和甘油三酯水平的作用,但以1000～2000 mg/kg的效果较为显著。在实验Ⅱ中,采用2×2双因素实验设计,研究了2种饲料类型(对照组和高糖高脂饲料)和2个烟酸水平(100 mg/kg和1000 mg/kg)对初始体重(24.45±0.07) g实验鱼生长、饲料利用、血脂水平和体成分的影响。养殖8周。结果发现,饲料类型或烟酸水平未对实验鱼的末体重、增重率、特定生长率、肥满度、脏体比和肠脂比,以及全鱼粗脂肪、粗蛋白、水分和灰分含量等生长性能指标产生显著影响(P0.05);对饲料粗蛋白和粗脂肪的表观消化率、饲料系数、摄食率等饲料利用指标也未产生显著影响(P0.05)。与投喂对照组饲料的相比,投喂高糖高脂饲料的实验鱼对饲料干物质和总能的表观消化率,及其血清胆固醇、甘油三酯和游离脂肪酸水平,肝脏、内脏、腹肌的粗脂肪含量显著升高(P0.05);而投喂高水平烟酸实验鱼的血清低密度脂蛋白、胆固醇和游离脂肪酸水平,肝脏粗脂肪含量则显著降低(P0.05)。饲料类型和烟酸水平仅对实验鱼血清的高密度脂蛋白和胆固醇水平存在显著的交互作用(P0.05)。结果表明,饲料中添加1000 mg/kg烟酸不会影响吉富罗非鱼的生长性能和饲料利用,并具有降低血脂水平和肝脏脂肪含量的作用。     

军曹鱼幼鱼对吡哆醇的需要量

以初始体重(3.23±0.06)g的军曹鱼为研究对象,以酪蛋白(不含维生素)、明胶、鱼肉浓缩蛋白为蛋白源,在基础饲料中分别添加0、2、4、8、16和32mgPN/kg,配制出6种实验饲料,使饲料中吡哆醇的水平分别达到0.22、1.89、3.87、7.54、14.75和29.88mgPN/kg,研究军曹鱼对吡哆醇的需要量。养殖实验在室内流水系统中(250L)进行,每个处理设3个重复,每个重复放养军曹鱼25尾。养殖实验过程中,海水盐度为30～34,水温28～32℃,溶氧>7mg/L,养殖实验持续9周。实验结果显示,在0.22～3.87mgPN/kg水平范围内,随着饲料中吡哆醇含量的升高,实验鱼特定生长率显著升高,当饲料吡哆醇水平达到或高于3.87mg/kg时,各饲料组实验鱼的特定生长率(2.68～2.71%/d)无显著差异,而都显著高于0.22和1.89mg/kg饲料组的特定生长率(1.17～2.06%/d)P<0.05)。军曹鱼肝脏吡哆醇含量、吡哆醛含量、谷丙转氨酶活力、谷草转氨酶活力均与特定生长率有相似的变化趋势,即在3.87mg/kg饲料组接近或者达到最大值,在达到或超过3.87mg/kg时达到或近似达到一...     

尖头金线鲤人工繁殖初步研究

用人绒毛膜促性腺激素(HCG)、促黄体素释放激素类似物(LRH-A2)、马来酸地欧酮(DOM)组合对尖头金线鲃(Sinocyclocheilus oxycephalus)催产获得成功,用鲤脑垂体5 mg/kg和人绒毛膜促性腺激素1 000 IU/kg组合催产失败.采取2次注射(第1次注射LRH-A2 2μg/kg,第2次注射LRH-A2 8μg/kg+DOM 3 mg/ks+HCG1 000 IU/kg)催产效果明显;采取遮光孵化,孵化率明显提高.     

饲料中添加维生素C对翘嘴鲌鱼种生长及组织中抗坏血酸含量的影响

在翘嘴(Culter alburnus)鱼种基础饲料中添加相当于抗坏血酸含量为0 mg/kg、25 mg/kg、50 mg/kg、100 mg/kg、150 mg/kg、200 mg/kg和400 mg/kg的包膜维生素C(Vc),制成7种实验饲料,饲养初始体质量为(3.71±0.11)g的7组翘嘴鱼种8周,每个实验组包含3个重复。结果表明,摄食不添加Vc饲料的实验鱼成活率显著低于其他Vc添加组(P<0.05)。饲料中Vc添加量为0~50 mg/kg时,对鱼体增重有显著影响(P<0.05),鱼体增重随添加量的增加而上升。但添加量继续增大,对鱼体增重不再有显著影响(P>0.05)。饲料中维生素C添加量为0和25 mg/kg时,饲料效率和蛋白质效率低于其他各组(P<0.05)。试验饲料中Vc不同添加量对肝体指数和全鱼体成分无显著影响(P>0.05)。肌肉中抗坏血酸含量随饲料中Vc添加量加大而不断上升,二者呈正相关关系(P<0.05)。肝胰脏抗坏血酸含量在Vc添加量≤100 mg/kg时,随饲料中Vc添加量加大而不断上升(P<0.05),但高于此添加量时,则肝胰脏中抗坏血酸不再随添加量的上升而有显著变化(P>0.05)。分别以鱼体增质量和肝胰脏中抗坏血酸为指标,经折线模型(Brokenline model)回归分析求得翘嘴鱼种饲料中Vc的适宜添加量分别为53 mg/kg和97 mg/kg。[中国水产科学,2007,14(1):106-112]     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.