栉孔扇贝生殖活动前后的滤食和生长

在桑沟湾用模拟现场流水法对栉孔扇贝的摄食生理进行了比较研究。结果表明，栉孔扇贝在进行生殖活动前后滤水率无明显的差异，但进行生殖活动前的摄食量较大。尽管栉孔扇贝的滤水率和摄食量随着个体的增大而增加，它的吸收率却与个体大小无关。在３００￣６００ｍｌ／ｍｉｎ的水流范围内栉孔扇贝的滤水率没有明显的变化，水流小于３００ｍｌ／ｍｉｎ时扇贝的滤水率则明显降低。根据实验数据，用计算机模拟得出了栉孔扇贝在生殖活动前     

栉孔扇贝对环境变化适应性研究一盐度、pH对存活呼吸、摄食及消化的影响

取体长分别为3和5 cm的栉孔扇贝(Chlamys farreri)置室内水泥池流水暂养1周后,进行盐度和pH变化对其存活、呼吸、摄食及消化影响的实验.结果表明, 栉孔扇贝96 h的半致死盐度为25.在不同盐度的海水中暴露24 h的实验结果为,栉孔扇贝随盐度的降低,出现耗氧率升高,随后逐渐下降,到盐度15时不再耗氧而死亡;滤水率和淀粉酶活性随盐度降低而降低,盐度为15时完全不滤水,淀粉酶完全失去活性.小个体栉孔扇贝耐低盐能力较大个体的略大些.pH降至7.8以下时开始对栉孔扇贝的存活产生影响,降至7.6时,48 h后死亡率为35%左右;7.2时达50%;降至7.0时扇贝不能存活.大个体栉孔扇贝对海水pH变化略敏感于小个体.     

栉孔扇贝对环境变化适应性研究－温度对存活、呼吸、摄食及消化的影响

取体长分别为 ３和 ５ ｃｍ 栉孔扇贝（Ｃｈｌｙｍｙｓ ｆａｒｒｅｒｉ）置室内水泥池流水暂养 １周后进行实验。结果表明，栉孔扇贝 ９６ ｈ的半致死温度为 ２７～２８℃，导致其耗氧率突然升高和滤水率急剧下降的温度为 ２６℃，体内淀粉酶活性下降的温度为２７℃。因此确定，栉孔扇贝的适宜极限高温为２７℃。在水温２７℃持续９６ ｈ后，扇贝呼吸量迅速增大，随后减弱，摄食和消化能力逐渐降低；在 ２７℃持续 ５ ｄ，死亡率为 ５０％， ７ ｄ时全部死亡；在相同温度下，个体小的较个体大的耐高温程度要强一些。     

栉孔扇贝面盘幼虫和稚贝的滤水率昼夜节律

采用静水法研究了在水温18±0.5℃、饵料密度1.0×104 cell/ml下栉孔扇贝面盘幼虫滤水率的昼夜节律;在水温24℃±0.5℃、饵料密度3.0×104 cell/ml下栉孔扇贝稚贝(壳长1.177～2.017 mm)滤水率的昼夜节律.栉孔扇贝面盘幼虫和稚贝的滤水率分别于17:00、21:00、01:00、05:00、09:00和13:00测定.栉孔扇贝面盘幼虫和稚贝的滤水率均具有明显的昼夜节律,且二者相似.在白天滤水率较低,最低值出现在09:00～13:00,幼虫为0.002 6 ml/h · ind,稚贝为0.1231 ml/h·ind;在夜间有较高的滤水率,最大值出现在凌晨21:00～01:00,幼虫达0.025 8 ml/h·ind,稚贝达0.509 6 ml/h·ind.统计分析表明,栉孔扇贝稚贝和面盘幼虫的滤水率昼夜差异显著(P＜0.01).     

大连獐子岛海域虾夷扇贝养殖容量

现场测定了獐子岛海域的叶绿素a浓度、初级生产力的季节性变化和养殖虾夷扇贝的种群结构;采用生物沉积法,测定了不同规格的虾夷扇贝的滤水率和虾夷扇贝的基本生物学特性.调查结果显示,叶绿素浓度在1.23～2.85 mg·m-3范围内,均值为(1.78±0.57)mg·m-3;初级生产力的平均值为(76.6±41.9)mg C·m-2·d-1,虾夷扇贝单位个体的滤水率为(0.55±0.25)L·h-1.结合虾夷扇贝的年产量、海域面积和有关的水文状况等数据,计算了食物限制性指标的数值,摄食压力和调节比率在0.05和1.0之间,而滤水效率小于0.05.结果显示,由于该海域的叶绿素浓度和初级生产力水平较低,海水流速大,因此,水交换带来的悬浮颗粒物为主要食物来源.目前的虾夷扇贝的养殖量(32亿粒)接近生态容量,如果开展筏式养殖,利用整个海域的水体,养殖量增大20倍的空间并达到养殖容量,预计年产量将达到256亿粒.     

光照对不同规格番红砗磲(Tridacna crocea)氧、氨氮及活性磷酸盐代谢的影响

在水温24–26℃下,采用室内实验生态学方法,研究了5000 lx光照强度和黑暗对壳长为(63.53±1.22)mm(S组)、(75.87±1.50)mm(M组)和(92.75±3.02)mm(L组)番红砗磲(Tridacna crocea)氧、氨氮及活性磷酸盐代谢的影响。结果显示,光照条件下,番红砗磲释放氧气,吸收氨氮和活性磷酸盐。黑暗条件下,番红砗磲代谢状况与其他双壳贝类类似。番红砗磲个体代谢率与规格密切相关:光照条件下个体越大,产氧率、对氨氮和活性磷酸盐吸收率越高;黑暗条件下,个体越大,耗氧率、对氨氮和活性磷酸盐释放率亦越高。光照条件下,番红砗磲软体部单位干重代谢率与其个体规格呈负相关,个体越大,单位干重的产氧率、氨氮和活性磷酸盐的吸收率越小。实验首次量化了不同光照条件下番红砗磲对氧、氨氮及活性磷酸盐的吸收和排泄状况,结果可为研究番红砗磲在珊瑚礁生态系统中的作用提供依据,对砗磲人工养殖也具有一定的参考。     

光照对不同规格番红砗磲(Tridacna crocea)氧、氨氮及活性磷酸盐代谢的影响

在水温24-26℃下,采用室内实验生态学方法,研究了5000 lx光照强度和黑暗对壳长为(63.53±1.22) mm(S组)、(75.87±1.50) mm (M组)和(92.75±3.02) mm (L组)番红砗磲(Tridacna crocea)氧、氨氮及活性磷酸盐代谢的影响.结果显示,光照条件下,番红砗磲释放氧气,吸收氨氮和活性磷酸盐.黑暗条件下,番红砗磲代谢状况与其他双壳贝类类似.番红砗磲个体代谢率与规格密切相关:光照条件下个体越大,产氧率、对氨氮和活性磷酸盐吸收率越高;黑暗条件下,个体越大,耗氧率、对氨氮和活性磷酸盐释放率亦越高.光照条件下,番红砗磲软体部单位干重代谢率与其个体规格呈负相关,个体越大,单位干重的产氧率、氨氮和活性磷酸盐的吸收率越小.实验首次量化了不同光照条件下番红砗磲对氧、氨氮及活性磷酸盐的吸收和排泄状况,结果可为研究番红砗磲在珊瑚礁生态系统中的作用提供依据,对砗磲人工养殖也具有一定的参考.     

饵料密度、体重和盐度对黄边糙鸟蛤滤水率的影响

2011年11～12月,以扁藻(Platymonas subcordiformis)为饵料,在实验室条件下采用静水法测定了不同饵料密度、体重和盐度下黄边糙鸟蛤(Trachycardium flavum)的滤水率。结果表明:饵料密度、体重以及盐度对黄边糙鸟蛤滤水率均存在显著性影响。在实验饵料密度范围内,当饵料密度小于10×104cell·mL-1时,黄边糙鸟蛤的滤水率随着饵料浓度的增加而增大,饵料浓度与滤水率之间呈现正相关的幂函数关系;体重对滤水率的影响呈幂函数关系,个体滤水率随着体重的增加而增大;在一定盐度范围内,滤水率随着盐度的升高而增大,在盐度为32.7时滤水率达到最大值0.249 L·(g·h)-1,随后随着盐度的升高滤水率呈下降趋势。     

温度对橄榄蛏蚌滤水率的影响

在实验室条件下,测定不同温度下橄榄蛏蚌(Solenaiaoleivora)的滤水率。结果表明,在15℃、20℃、25℃、30℃4个温度梯度下,橄榄蛏蚌的滤水率呈一个峰值变化,滤水率最大值出现在20℃,最小值出现在30℃;对于大规格和小规格橄榄蛏蚌,最大值分别为0 2388L/(ind·h)和0 1353L/(ind·h),最小值分别为0 0607L/(ind·h)和0 0358L/(ind·h)。方差分析(ANOVA)表明,温度和个体大小对橄榄蛏蚌的滤水率有极显著影响(F>F0 01),并且不同规格的橄榄蛏蚌,小规格组滤水率大于大规格组滤水率。此结论与多数双壳贝类的生理现象一致,即在一定温度范围内,温度越高,生理活动越旺盛;温度过高或过低均能使生物生理活动能力降低。     

长牡蛎壳金选育系F4与普通养殖群体摄食和呼吸的比较研究

为了从生理学角度探讨长牡蛎壳金选育系的快速生长机制,本研究以两种规格长牡蛎(Crassostrea gigas)第4代壳金选育系(简称金1和金2)和两种普通养殖群体(简称对照1和对照2)为材料,比较了不同温度(16℃、20℃、24℃、28℃、32℃)和盐度(15、20、25、30、35)条件下各实验组的滤水率(FR)和耗氧率(OCR)。结果显示:(1)摄食实验中,4个组长牡蛎的滤水率均随温度或盐度增加先上升后下降,在温度28℃时出现最大值;对照1的滤水率在盐度25时达到最大值,其他3组滤水率在盐度30时达到最大值;方差分析结果显示,温度、群体,盐度、群体对长牡蛎的滤水率均有显著性影响,长牡蛎壳金选育系的滤水率均显著大于普通养殖群体(P0.05)。(2)呼吸实验中,较大规格长牡蛎壳金选育系的耗氧率受温度或盐度变化的影响更小。方差分析结果显示,温度、群体,盐度、群体均对长牡蛎耗氧率有显著性影响。实验温度范围内,金1的耗氧率显著小于对照1,但金2的耗氧率显著大于对照2(P0.05)。实验盐度范围内,壳金选育系的耗氧率均显著大于普通群体(P0.05)。(3)同一壳色群体中,个体越大,单位软体部干重滤水率和耗氧率越低。研究表明,较大规格长牡蛎壳金选育系F4更能适应外部环境的变化,该选育系的快速生长可能是由其较高滤食行为导致的。     

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.