东海有尾类数量分布

根据1997~2000年东海23°30′~33°N、118°30′~128°E海域4个季节海洋调查资料,探讨了东海有尾类数量分布和季节变化。结果表明:秋季有尾类丰度最高,均值为149 ind/100m3,夏季38 ind/100m3,冬季20 ind/100m3,春季9 ind/100m3;有尾类数量在冬春夏季与水温和盐度相关关系不显著,秋季与表温有显著的正相关关系。有尾类数量季节变化机制具有暖水种的特征,这些特征形成与其优势种适温适盐特性有密切的关系。东海有尾类的数量波动,与东海暖流势力消长有密切的联系,也同暖流势力从夏到秋季维持一段时间有密切的关系。在东海,暖流势力较强的海域往往可以成为有尾类高丰度分布区域。秋季有尾类高分布区出现,对东海北部外海绿鳍马面鲀(Navodon septentrionalis)渔场和东海南部的带鱼(Trichiurus lepturus)和日本鲭(Scom ber japonicus)等多种经济鱼类渔场的形成有重要意义。     

东海浮游糠虾类优势种的研究

根据1997~2000年东海23°30′~33°N、118°30′~128°E海域4个季节海洋调查资料,用生态特征指标分析和聚集强度测度等研究方法,分析了东海浮游糠虾类优势种的数量变化和生态适应。结果表明,春、夏和冬三季糠虾类占优势的有漂浮囊糠虾(Gastrosaccus pelagicus)、中华节糠虾(Siriella sinensis)和美丽拟节糠虾(Hemisiriella pulchra)等3种,属暖温种。秋季优势种有四刺端糠虾(Doxomysis quadrispinosa)、宽尾刺糠虾(Acanthomysis latiscauda)和极小假近糠虾(Pseudanchialina pusilla)等3种,属暖水种。东海浮游糠虾类暖温种丰度低,出现率和聚集强度较低;暖水种相反,往往具有较高的丰度、聚集强度和出现率。     

东海浮游十足类数量分布与环境的关系

根据1997~2000年东海23°30′~33°N、118°30′~128°E海域4个季节海洋调查资料,运用定量、定性方法,探讨东海浮游十足类(Decapods)总丰度的平面分布、季节变化以及变化的动力学机制。结果表明,浮游十足类总丰度有明显的季节变化,夏季最高为451 ind/(100 m3),秋季次之为71 ind/(100 m3),春季最低为24 ind/(100 m3)。北部近海(29°30′~33°N、123°30′~125°E)水域春季几乎没有分布,除冬季外,总丰度基本呈近海高于外海的分布趋势。中型莹虾(Luciferintermedius)是影响总丰度变化最主要的种类;夏季与秋季及四季总丰度的变化同水温有非常显著的线性相关关系,与盐度的相关关系不显著;冬季则仅仅与盐度有关,春季则与温度和盐度相关。从春季到夏季,高丰度区随台湾暖流向北扩展,并在闽浙沿岸水团与台湾暖流交汇处形成高丰度分布区[>2 500 ind/(100 m3)];从夏季到秋季,浮游十足类随着台湾暖流继续向北,在与长江冲淡水交汇处形成较高丰度区。水温和海流是影响东海浮游十足类总丰度分布的主要环境因子。     

长江口邻近海域浮游十足类生态特征

摘要：根据2002~2003年长江口29°00´~32°00´N、122°00´~123°30´E海域4个季节的海洋调查资料，运用定量、定性方法，探讨了长江口邻近海域浮游十足类丰度的季节变化、水团对丰度分布的影响、优势种对总丰度的贡献以及其生态适应特征。结果表明，长江口邻近海域浮游十足类丰度季节变化主要受温度影响，平面分布变化主要受盐度影响。夏季平均丰度最高(10.42 ind/m3)，主要集中在长江口羽状锋(122°40′~123°30′ E)处，冬季丰度最低（0.004 ind/m3）。中型莹虾(Lucifer intermedius)和细螯虾(Leptochela gracilis)是最主要的优势种。夏季，中型莹虾的贡献率(0.97)远大于细螯虾(0.12)。中型莹虾平均丰度夏季最高(8.93 ind/m3)，春季为0.28 ind/m3，秋季为0.14 ind/m3，冬季最低 (0.005 ind/m3)。细螯虾在春季平均丰度0.11 ind/m3， 夏季0.67 ind/m3，秋季0.13 ind/m3，冬季0.004 ind/m3。     

东海赤潮高发区春季浮游桡足类与环境关系的研究

根据2002年4-5月东海122°00′～123°30′E、29°00′～32°00′N海洋综合调查资料,对东海赤潮高发区春季浮游桡足类种类组成、优势种、群落特征及其与环境和赤潮生物的关系作了探讨.结果表明共鉴定桡足类40种,优势种有中华哲水蚤(Calanus sinicus)、真刺水蚤幼体(Eucheta larvae)、精致真刺水蚤(Euchaeta concinna)等,并以中华哲水蚤占绝对优势.桡足类总丰度均值为154.97 ind·m-3(5.00～649.85 ind·m-3),最高丰度区(＞500 ind·m-3)主要分布于长江口30°30′～31°15′N、123°15′E以东水域.多样性指数值在长江口以北是近海高于外海,长江口以南是外海高于近海.桡足类种类数与表层水温(℃)有非常显著的正相关性(R=O.713,P＜0.01).桡足类总丰度与表层水样中硅藻丰度,桡足类总丰度与夜光藻丰度呈非线形相关关系,前者可用肥力与产力模型描述,后者可用有效积温模型表达.     

黄海南部及东海中小型浮游桡足类生态学研究Ⅰ.数量分布

根据1981年2-11月在黄海南部及东海(28°～34°N、121°～127°E)海域进行的4个季节的海洋调查资料,对该海域中型浮游生物网采集的中小型浮游桡足类丰度作了探讨.结果表明调查区桡足类总丰度4季均值为376.40ind·m-3,夏季(846.34 ind·m-3)＞春季(338.91 ind·m-3)＞秋季(204.96 ind·m-3)＞冬季(115.41 ind·m-3).黄海南部(32°N以北)和东海(28°～32°N)调查海域4季均值分别为271.05 ind·m-3和403.59 ind·m-3,季节变化趋势与全调查区一致,但在夏季,黄海南部平均丰度(492.04 ind·m-3)明显低于东海(938.2 ind·m-3).根据优势度和回归贡献分析表明冬、春、夏3季总丰度分布主要取决于拟长腹剑水蚤(Oithona similis)、小拟哲水蚤(Paracalanus parvus)和近缘大眼剑水蚤(Corycaeus affinis)等的分布,而秋季主要取决于尖额保猛水蚤(Aegisthus mucronatus)、孔雀丽哲水蚤(Calocalanus pavo)和锦丽哲水蚤(Calocalanus pavoninus)等.文中还对影响中小型浮游桡足类总丰度分布的主要因子盐度、水温和水系等与总丰度的关系进行了探讨.     

东海管水母类生态研究

根据1997-2000年东海23°30′33°00′N、118°30′～128°00′E海域4个季节海洋调查资料,对东海管水母类种类组成及优势种、数量分布、生态类群等作了探讨.结果表明鉴定到种的管水母类有40种,其中宽板无棱水母(Sulculeolaria bigelowi)为东海区首次记录;主要优势种有五角水母(Muggiaea atlantica)、双生水母(Diphyes chamissonis)和拟细浅室水母(Lensia subtiloides)等.管水母类总丰度春季最高(491 ind·10-2·m-3)、夏季最低(66 ind·10-2·m-3);平面分布不均匀,一般东海近海高于外海和台湾海峡海域.东海管水母类可分为3个生态类群,数量上以近岸低盐广温类群占优势,65%的种类由广高温高盐类群构成.     

东海浮游磷虾类的数量分布

根据1997-2000年东海23°30′～33°N、118°30′～128°E海域4个季节海洋调查资料,运用定量、定性分析方法,探讨了东海浮游磷虾类总丰度的平面分布、季节变化,相应的动力学及与渔场的关系。结果表明,东海磷虾类总丰度秋季最高,春季次之,冬季最低;冬,春,夏季的小型磷虾(Euphausianana)和秋季的中华假磷虾(Pseudeuphausiasinica)对总丰度的贡献较大,是影响磷虾类总丰度变化的主要优势种;冬、春和秋季总丰度与水文环境因子的线性相关性不显著,夏季总丰度与底层温度和10m层盐度的二元线性相关关系非常显著。秋季磷虾高丰度区位于台湾暖流与各水团的交汇处。磷虾类总丰度的变化动力来自水团的影响和主要优势种对总丰度变化的回归贡献,后者与优势种的生态习性有关。磷虾类秋季高丰度区的分布与带鱼、小黄鱼和日本鲭索饵场的位置基本一致。     

黄海南部、东海北部夏秋季小黄鱼数量分布及与浮游动物的关系

对夏秋季黄海南部、东海北部海域的小黄鱼和浮游动物的数量分布及其它们之间的关系进行了研究,结果表明:夏秋季节,黄海南部、东海北部小黄鱼主要出现在大沙、江外、吕四和沙外渔场,夏季最高生物量分布区出现在长江口和江外渔场交界处的31°30′N、125°00′E海域,秋季最高生物量分布区出现在大沙和沙外渔场交界处的32°30′N、125°00′E海域。2个季节浮游动物优势种的组成主要以浮游甲壳动物、浮游幼体以及毛颚类动物为主。浮游动物有2个密集分布区:一个在近岸一侧123°00′E经度线附近,夏季呈南北方向分布,秋季呈西北-东南走向;另一个在32°00′N、125°00′E附近海域。从夏季到秋季,浮游动物优势种的组成有了较大的更替,优势种的范围更加扩大;夏季占绝对优势的中华哲水蚤到秋季已经不在优势种之列。夏秋季小黄鱼主要分布区与浮游动物的高密度分布区存在着良好的对应关系。夏季小黄鱼和其他浮游食性鱼类的强烈的摄食影响可能造成了秋季浮游动物丰度的急剧下降。小黄鱼主要分布区内饵料浮游动物优势种的季节变化可能对其食物选择的变化有重要的影响。     

东南太平洋智利竹筴鱼渔场浮游生物数量分布及与渔场关系

2006年6~8月,对智利外海渔场的5个站点(31°00′~40°45′S、82°05′~91°52′W)进行了浮游生物调查。结果显示,浮游植物共有7属10种,其中硅藻门有5属5种,甲藻门1属3种,蓝藻门1属2种;浮游植物平均生物量为0.416 mg/m3,最高生物量为0.822 mg/m3,最低为0.13 mg/m3。浮游动物为33属40种,其中桡足类有14种,占总种类数的35%,其次为浮游幼虫、水螅水母类、糠虾类和磷虾类等;浮游动物平均生物量为0.656 mg/m3,最高丰度为211 ind/m3,最低为33.5 ind/m3。通过对智利竹筴鱼产量及CPUE(单位渔获量努力量)叠加分析,发现中心渔场区域主要集中于38~43°S、80~83°W范围内,与各采样站点浮游植物生物量分布趋势一致,中心渔场与表层浮游动物生物量的分布尚不存在相对应的关联。     

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.     

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.     

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.