东南山丘区水库流域多空间尺度景观格局对水质的影响

为探讨东南山丘区水库流域不同空间尺度下景观格局对水质的影响，基于珊溪-赵山渡水库上游支流15个监测断面水质及流域土地利用数据，提取子流域和6种河岸带缓冲区空间尺度上的景观格局信息，运用冗余分析方法定量探讨不同尺度景观格局与水质的关系，识别水质资源管理的最佳空间尺度及关键景观指标。结果表明(1)水质指标时空尺度上存在显著差异，其中pH、总氮、氨氮空间差异显著(P<0.05)，里光溪、南浦溪、莒江溪及玉溪为主要污染风险区域，总氮浓度表现为雨季低于旱季；(2)流域内林地和草地占比最大，为主要的“汇”景观，建设用地、耕地为主要“源”景观，最大斑块指数(LPI)对水质改善具有积极作用，散布与并列指数(IJI)、香农多样性指数(SHDI)在多数时空尺度均会导致水质下降；(3)景观格局对水质的影响存在空间尺度效应，100 m及800 m河岸带尺度总解释率优于其他尺度，雨季水质主要受草地、林地、建设用地、水域、LPI和SHDI的影响，旱季水质主要受建设用地、耕地和IJI影响。该研究表明，流域内景观格局对水质影响的最佳管理尺度为800 m河岸带，优化该尺度内的景观格局，综合考虑近水体“源”景观的集聚，防控100 m河岸带污染物排放与迁移，对于保障珊溪-赵山渡水库饮用水安全具有重要意义。     

杞麓湖浮游植物群落结构对富营养化的响应及鱼产力评估

杞麓湖位于云南省通海县城郊，是受人类干扰较为严重的高原浅水型湖泊之一。为了解杞麓湖的浮游植物群落结构及富营养化现状，于2021年对杞麓湖浮游植物和富营养化相关水质参数进行了4次调查，并对其鱼产力进行了评估。结果显示：杞麓湖浮游植物有8门116属213种，其中绿藻门种类数最多，有118种；伪鱼腥藻(Pseudoanabaena sp.)为全年优势种，且优势度较大；浮游植物密度和生物量均值分别为(50.442±4.479)×10⁷ ind./L和(20.132±2.208) mg/L,均以蓝藻门为主；非度量多维尺度分析(NMDS)表明浮游植物群落结构存在显著的季节差异；浮游植物的Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数的均值分别为1.691±0.081、0.490±0.021和1.537±0.066;综合营养状态指数(TLI)均值为76.3,显示杞麓湖处于重度富营养状态；杞麓湖浮游植物可提供的鱼产力为1 843.59 t。综上所述，杞麓湖富营养化严重，湖区藻类密度较高且利用率偏低，建议加大鲢(Hypophthalmic...     

云南九大高原湖泊流域现行管理体制及其完善建议

云南省湖泊面积达到30 km2以上有9个,分别为滇池、阳宗海、抚仙湖、星云湖、杞麓湖、洱海、泸沽湖、程海和异龙湖,具有独特的自然地理条件和生态服务功能,在全省经济发展和生态文明建设中占有举足轻重的地位。近年来对9大高原湖泊的治理已取得一定成效,但水质日趋恶化仍是当前面临的突出问题,主要原因是现行的湖泊流域管理体制机制不够完善,未能适应流域经济的快速发展以及流域保护治理的需求。分析和总结了云南9个高原湖泊流域管理体制的现状及存在的问题,在国内外湖泊流域管理案例和成功经验的基础上,根据9大高原湖泊流域自身特点,提出了完善管理体制的建议。     

1980-2018年扎龙湿地及乌裕尔河流域景观格局演变及其响应

研究扎龙湿地及其上游乌裕尔河流域的景观格局演变，为湿地生态系统的管理与保护提供参考。利用研究区内1980-2018年5期土地利用遥感数据，运用GIS空间分析和主成分分析法，分析了区域景观格局时空变化及其驱动力。结果表明：（1）耕地面积从1980年的8629.648629km2增加至2018年的9527.909528km2；水域面积、居工地面积和盐碱地面积分别增加45.7446、57.9358和18.4618km2；林地面积、草地面积和沼泽地面积分别减少231.90232、742.33743和46.1646km2。1980-2000年研究区域其他土地利用类型转移为耕地的面积1035.861306km2，草地转移为其他土地利用类型的面积845.85846km2，其他土地利用类型面积总体变化不大。（2）景观格局指数不稳定，沼泽湿地面积是扎龙湿地的优势景观类型，耕地是乌裕尔河流域的优势景观类型，除优势景观类型外各种景观类型破碎化严重，景观丰富度越来越低。（3）景观格局的变化是自然气候和社会经济发展共同作用的结果，社会经济变化中的人均GDP、第一产业值以及城镇人口数量是导致整个研究区域湿地景观格局变化的主要驱动力；年均径流量与扎龙湿地内部草地的变化正相关。     

大头鲤常见疾病防控技术

大头鲤,隶属鲤形目、鲤科、鲤亚科、鲤属,当地俗称“大头鱼、碌鱼”,曾分布于星云湖、杞麓湖,历史上是云南四大名贵鱼类之一,2011年被评为云南六大名鱼之一。上世纪八、九十年代由于过度捕捞和水域生态环境变化,种群数量和产量急剧下降,     

大头鲤人工繁养殖技术

大头鲤是云南星云湖和杞麓湖特有的土著经济鱼类,具有较高的经济价值和研究价值。由于星云湖水质下降等多种因素的影响,自然水域的大头鲤已濒临绝迹。为拯救和开发利用大头鲤资源,江川大头鱼原种站对大头鲤的人工驯养、繁殖、苗种培育、成鱼养殖、病害防控和大水面增殖技术等进行了十多年的试验研究。文章介绍了大头鲤的人工繁养殖技术。     

基于LUCC的鄱阳湖湿地生态效应分析

土地利用/土地覆盖变化(LUCC)是内陆湿地演变的重要因素之一,对湿地生态系统产生广泛的生态效应。2000年以来,鄱阳湖湿地土地利用方式和强度发生了较大变化,有必要探究由此引发的生态效应。利用2000-2013年共4个时期的遥感影像,借助RS和GIS工具研究了鄱阳湖湿地各时期的LUCC及其动态度和土地利用综合程度指数,通过景观指数计算,分析了总体景观格局和不同景观类型的变化特征;利用主成分分析和相关分析方法,探讨了总体景观格局指数主成分综合值及其与土地利用程度综合指数的相关性。结果表明,鄱阳湖湿地土地利用结构和方式发生了较大变化,水体和耕地面积逐年下降,林地、建设用地和沙滩地面积逐年增加,土地利用综合程度指数由2000年的249.08上升到2013年的251.41,土地利用强度持续增加;总体景观格局指数和不同景观类型均发生了较大变化,景观趋于多样化、复杂化和破碎化,连通性降低,稳定性变弱;土地利用程度综合指数与总体景观格局指数相关系数为0.927,呈显著正相关,土地利用强度的增加使鄱阳湖湿地景观格局趋于负面化。研究结果反映LUCC引发景观的破碎化和不稳定、鄱阳湖湿地面积的减少以及生物多样性降低等一系列负向生态效应。     

扬州市湿地景观格局演变及驱动力研究

以扬州市2002年、2007年、2013年的遥感影像为数据源,通过解译获得了扬州市湿地资源分布图,运用转移矩阵法及景观格局指数法对2002-2013年间扬州市湿地动态变化及景观格局演变进行分析,并利用主成分分析法对其驱动力进行探究。结果表明,扬州市2002-2013年湿地面积呈逐年下降趋势,2007年比2002年减少13.69 km2,降幅1.1%;2013年比2007年减少43.23 km2,降幅3.3%。2013年与2002年相比,河流面积稍有减少,降幅为5.6%;滩地面积增加73.2%;库塘面积所占比重由49.84%上升到55.37%,面积增加6.2%;湖泊面积降幅29.7%,所占比重由32.83%下降到24.14%。2002、2007、2013年,各湿地斑块所占景观面积比均为库塘>湖泊>河流>滩地。景观格局指数分析表明,湖泊、滩地及库塘呈现不同程度的破碎化,而河流湿地斑块形状趋于规则且连通性较好。扬州市湿地景观整体呈破碎化趋势,湿地斑块形状趋于复杂,景观多样性增加,各类型湿地呈均衡化趋势发展。社会经济发展、人口增加、第二产业比重及降雨量变化是导致湿地景观格局变化的主要驱动力。     

南太湖入湖口蓝藻生物量与氮营养因子的年变化特征以及相关性研究

为了解南太湖水域近年来水质状况,以及蓝藻生物量与氨氮和总氮之间的变化规律,实验采用统计学方法,对南太湖水域3个入湖口(小梅港、新塘港、大钱港)水质中蓝藻生物量、氨氮和总氮的年变化特征进行了调查;使用SPSS10.0中的Bivariate(pcarson)软件对蓝藻生物量与氨氮和总氮的相关性进行了分析。结果表明:(1)南太湖入湖口蓝藻生物量一般有两个高位期,一个是在每年5—6月,另一个在每年的9—10月;(2)南太湖入湖口的总氮浓度处于富营养水平,并有向重富营养化发展的迹象;(3)蓝藻生物量与氨氮浓度的相关性系数r介于0.102～0.290,呈现不相关;(4)2008—2009年蓝藻生物量与总氮浓度的相关系数r介于0.010～0.210,呈现不相关;2010年蓝藻生物量与总氮浓度的相关系数r介于0.430～0.474,呈现低度负相关。结果说明南太湖入湖口的氮营养盐已经不容忽视,湖泊中氨氮和总氮浓度升高,将为蓝藻的繁殖生长提供条件,蓝藻一旦暴发,氨氮和总氮浓度反而迅速降低,在南太湖水域蓝藻生物量与氨氮和总氮浓度之间存在一定的此消彼长规律。     

运城黄河湿地景观空间格局变化及其驱动因素

基于2007-2017年5期遥感影像,运用遥感解译和景观指数方法,探究运城黄河湿地景观格局变化及其驱动因素,为黄河中游河道湿地的修复与可持续利用提供参考。结果表明:(1)湿地面积在2007-2017年期间总体呈增长趋势,其中2007-2015年湿地面积持续上升,面积增加9 041.39 hm^2,2015-2017年减少5 716.08 hm^2。湿地与旱地之间转换最密切,湿地景观间(水域+沼泽+草甸)也有较大幅度的转换。景观类型的分布以河津市、万荣县、永济市及垣曲县部分种类偏多,湿地景观沿河流分布。(2)类型水平上,旱地是优势类型,湿地整体处于劣势,景观零碎。水域在湿地景观中占优势,林地、旱地景观趋于复杂,旱地、水域、林地景观集聚度偏大;景观水平上,研究区景观破碎度和复杂度都有不同程度的降低,结构趋于稳定,连通性变好。(3)景观格局变化主要受人为驱动影响,其中政策对研究区有强制性的作用。近10 a运城黄河湿地呈现增长态势,景观格局总体逐渐优化。     

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.