鸭绿江口浅海海域菲律宾蛤仔养殖容量估算

通过对鸭绿江口海域初级生产力生产量,浮游植物、浮游动物和底栖生物的丰度和生物量的调查,根据PARSONS-TAKAHASHⅡ营养动态模型Q=(BEn)×k,对鸭绿江口浅海菲律宾蛤仔养殖容量进行了估算.研究结果表明,不同季节壳长1.5、2.0、2.5cm的菲律宾蛤仔年养殖容量分别为189 356.60、221 970.71、249 717.05t,养殖容量春季最大,秋季次之,夏季最小.春季单位面积可放养菲律宾蛤仔:滩涂养殖平均为1.48 kg/m2,深水养殖为1.17 kg/m2;夏季单位面积可放养的菲律宾蛤仔:滩涂养殖平均为0.17 kg/m2,深水养殖为0.32 kg/m2.该区域菲律宾蛤仔实际养殖密度已经大大超过其单位面积最佳放养容量,这也是导致该区域菲律宾蛤仔疾病频发和死亡率高的主要原因.     

基于叶绿素a时空分布的胶州湾菲律宾蛤仔养殖容量评估

2017年7月~2019年4月期间，本研究采用大面观测、现场模拟实验与生长情况跟踪相结合的手段，基于Dame指标和Herman模型估算了胶州湾菲律宾蛤仔(Ruditapes philippinarum)的养殖容量。结果显示，调查期间，胶州湾水体的叶绿素a浓度为2.09~4.28 mg/m3，均值为3.07 mg/m3；不同规格(壳长2.29~3.59 cm)的菲律宾蛤仔单位个体的平均滤水率为0.45 L/(h?ind.)，单位重量菲律宾蛤仔的平均滤水率为2.52 L/(g?h)；菲律宾蛤仔1龄、2龄和3龄的平均干重分别为0.18、0.30和0.42 g；胶州湾的水团停留时间为52 d，初级生产时间为1.58 d，贝类滤水时间为2.09 d；1龄、2龄和3龄蛤仔的养殖容量分别为637、378和272 ind./m2。目前，菲律宾蛤仔养殖量已超过养殖容量，建议若以2龄蛤为采捕对象，适宜的播苗密度为582 ind./m2；若以3龄蛤为采捕对象，适宜的播苗密度为789 ind./m2。本研究结果可为保障胶州湾菲律宾蛤仔养殖产业的绿色高质量发展提供理论依据和数据支撑。     

福建诏安湾贝类养殖容量的研究

通过现场对诏安湾叶绿素a含量、初级生产力、生态效率、浮游植物有机碳含量、养殖贝类有机碳含量及其含壳重与鲜组织重比值、养殖贝类和野生滤食性动物滤水率、潮间带和潮下带及吊养区附着滤食性动物现存量等的调查获得模型参数,应用营养动态模型、沿岸能流模型估算贝类生态容量,进而扣除野生滤食性动物现存量形成贝类的养殖容量,同时采用贝类能量收支模型估算贝类养殖容量。3种模式估算的贝类养殖容量分别为58469t,288260×104ind;60275t,297167×104ind;61532t,30336×104ind;平均60092t,296263×104ind。并且采用统计分析法估算贝类及其各品种的适养面积。贝类适养总面积为2755hm2,其中缢蛏25hm2,牡蛎1560hm2,翡翠贻贝215hm2,菲律宾蛤仔120hm2,泥蚶30hm2,凸壳肌蛤95hm2,波纹巴非蛤710hm2。     

福建围头湾贝类的养殖容量

通过对围头湾的叶绿素a含量、初级生产力、潮下带、潮间带和吊养区非养殖滤食性动物现存量、养殖贝类有机碳含量及其含壳重与鲜组织重的比值等模型参数的调查测定和检测分析,并参照邻近大嶝岛海域的浮游植物有机碳含量、养殖贝类的滤水率和参照附近深沪湾的生态效率,采用营养动态模型和沿岸海域能流分析模型估算了该海域贝类生态容量,进而扣除野生滤食性动物现存量,估算贝类养殖容量；同时应用方建光模型估算贝类的养殖容量；还采用统计分析法估算贝类及其各养殖品种的适养面积,目的在于控制该海域贝类的养殖量和对各种贝类养殖量进行优化配置。3种模型估算的贝类养殖容量分别为111 720 t,508 246×10~4 ind；112 072 t,509 849×10~4 ind和114 504 t,520 789×10~4 ind,平均112 765 t,512 991 ind；适养面积为3 905 hm~2,其中牡蛎2 956 hm~2,缢蛏359 hm~2,菲律宾蛤仔489 hm~2,翡翠贻贝11 hm~2,凸壳肌蛤90 hm~2。1999年贝类养殖总面积1 894 hm~2,尚有2 011 hm~2可再扩大养殖的潜力。     

基于生态模型估算胶州湾菲律宾蛤仔养殖容量

贝类的养殖容量是养殖功能海域的生态系统所能容纳的最大养殖个体数量。本文由实测资料建立了胶州湾生态模型,计算了浮游植物生物量,进而依据饵料收支平衡关系,估算了胶州湾菲律宾蛤仔的养殖容量,研究结果表明,各养殖区不同规格蛤仔的养殖容量在1月或3月份最大,9月份最小;胶州湾5个养殖区内,2~2.6cm、2.6~3.3cm和3.3~4cm 3种壳长规格菲律宾蛤仔的平均养殖容量分别为603枚/m2、441枚/m2和362枚/m2,胶州湾菲律宾蛤仔的播放密度已经饱和;为了保持最大产量、提高养殖品质的同时并将苗种成本降至最低,可适当降低播放密度;建议红岛东、红岛南、红岛西、胶州、黄岛等5个养殖区菲律宾蛤仔的放养密度分别为718枚/m2、693枚/m2、557枚/m2、805枚/m2和654枚/m2,胶州湾平均放养密度为690枚/m2。     

基于生态系统动力学模型的胶州湾菲律宾蛤仔养殖容量动态评估

养殖容量评估是衡量贝类养殖活动是否环境友好、碳汇功能能否充分发挥的重要前提。本研究基于2018年5月—2019年2月的走航观测和定点连续观测数据,通过构建营养盐–浮游植物–浮游动物–碎屑–菲律宾蛤仔(nutrients–photoplankton–zooplankton–detritus–clams, NPZD-C)生态系统动力学模型,动态评估了胶州湾菲律宾蛤仔(Ruditapes philippinarum)的养殖容量。结果显示,构建的生态系统动力学模型能够较好地反演菲律宾蛤仔的生长和浮游植物的动态响应,菲律宾蛤仔和浮游植物的实测值和模拟值均呈显著线性相关(P<0.01),R2分别为0.934 8和0.926 4;不同放苗密度情境下的产量模拟结果显示,当苗种(2000~3000 ind./kg)的初始放苗密度分别为300、500、700、1000、1500 ind./m2时,蛤仔的预测产量分别为10.5、15.6、18.9、21.6、23.2 t/hm2;养殖容量评估结果显示,若在期望的10个月养殖时间内收获湿重为5 g以上的商品蛤仔,放苗密度需控制在1000 ind./m2以内,以生态效益和经济效益的最大化为判定标准,适宜的放苗密度为550~750 ind./m2。研究结果可为实施生态系统水平的胶州湾菲律宾蛤仔养殖管理、充分发挥菲律宾蛤仔的碳汇功能提供理论依据和科学指导。     

桑沟湾楮岛大叶藻床区域菲律宾蛤仔的生态贡献

桑沟湾楮岛大叶藻(Zostera marina L.)床周边存在大量的底栖菲律宾蛤仔(Ruditapes philippinarum),为摸清菲律宾蛤仔的生理活动与大叶藻的相互作用,2016年5~7月,在菲律宾蛤仔和大叶藻集中分布区,评估了菲律宾蛤仔种群资源量,现场流水法测定了菲律宾蛤仔个体水平的摄食、代谢生理,围隔实验法探讨了种群水平蛤仔与大叶藻的相互作用。结果显示,桑沟湾楮岛大叶藻床海区菲律宾蛤仔的平均生物量为(572.00±20.23) ind./m2,大(壳长为3.50~4.10 cm)、中(壳长为3.00~3.50 cm)、小(壳长为2.00~3.00 cm)规格各占9.01%、43.60%和47.38%。菲律宾蛤仔的排氨率、耗氧率、滤水率、摄食率分别为(0.44±0.15)~(1.40±0.35) μmol/(ind.·h)、(0.21±0.02)~(0.33± 0.08) mg/(ind.·h)、(0.69±0.38)~(0.83±0.66) L/(ind.·h)和(2.57±0.41)~(3.41±0.68) mg/(ind.·h),且都随体重的增加而增大。围隔实验设有3个实验组(蛤仔组、大叶藻组和大叶藻+蛤仔组),1个空白组,每组3个平行(大叶藻30茎枝左右、蛤仔15个左右),实验进行4 h。研究表明,蛤仔组、大叶藻+蛤仔组和大叶藻组间的溶氧浓度存在显著差异(P<0.05);蛤仔组与其他3组的氨氮浓度存在显著差异(P<0.05);蛤仔组、大叶藻+蛤仔组与空白组的水体颗粒物浓度存在显著差异(P<0.05),大叶藻组与空白组差异不显著(P>0.05)。桑沟湾楮岛海区菲律宾蛤仔养殖面积约为0.5 km2,蛤仔每天可以过滤46 t海水中的悬浮颗粒物,并为大叶藻提供0.4 t的氨氮。本研究为深入揭示大叶藻海区菲律宾蛤仔的生态作用提供了基础数据。     

饲养密度对条石鲷生长的影响

通过模拟工厂化养殖模式，采用单因素实验方法进行各体长阶段的密度梯度饲养试验。经过为期60的饲养管理后，对条石鲷的增长率及饵料系数进行比较分析，结果表明：适宜条石鲷工厂化养殖的各体长阶段放养密度：体长在10-13cm，养殖密度为80ind／m3；体长在14-16cm，养殖密度为52ind／m3；体长在17～20em，养殖密度为36ind／m3；体长在21—24cm，养殖密度为24ind／m3。     

菲律宾蛤仔滩涂生态养殖技术

为研究菲律宾蛤仔的滩涂生态养殖技术,在长江口以北的黄海海区滩涂进行了菲律宾蛤仔砂仔苗、白仔苗及中仔苗3种不同规格苗种的生态养殖试验。试验结果:大面积增养殖条件下,砂子苗、白仔苗及中仔苗的放养密度分别为2 700、760、667粒·m-2时,捕获量分别为(7.96±0.31)×10-2、(3.03±0.12)、(1.89±0.06)kg·m-2。小面积增养殖条件下,白仔苗和中仔苗的成活率与放养密度呈负相关。另外,滩涂养殖白仔苗经15~18个月养殖可采捕销售,亩产值7272元(15亩=1 hm2,下同);浅海底播养殖中子苗,经11个月的养殖可采捕销售,亩均产值5048元;在大规格苗种培育中,从砂仔苗(壳长1~3 mm)培育到白仔苗(壳长8~10 mm)需7个多月,亩产值1067元。     

大弹涂鱼池塘养殖技术

在面积为1公顷的池塘投放全长为2.5～3.0cm的大弹涂鱼苗60000尾,养殖密度为6尾/m2。经过1年的养殖,共收获成鱼1147.5kg,成活率达85%,体长9.30～14.50cm,平均体长11.80cm,体重11.2～38.3g,平均体重22.50g。     

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.