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。     

东海毛颚类优势种及与环境的关系

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,对东海毛颚类(Chaetognatha)优势种与环境的关系进行研究。结果表明,毛颚类优势种季节交替不明显,优势度最高的种分别是:夏季肥胖箭虫(Sagittaenflata)、冬、春季海龙箭虫(Sagittanagae)和秋季百陶箭虫(Sagittabedoti)。主要优势种中,百陶箭虫聚集强度指标值最高,其次是海龙箭虫,肥胖箭虫最低。肥胖箭虫与表层温度线性关系极其显著,肥胖箭虫和海龙箭虫与表层盐度的关系以及百陶箭虫与表层温度和表层盐度的关系符合YieldDensity模型。肥胖箭虫高丰度区往往位于台湾暖流与浙江沿岸流交汇处偏暖水的一侧,海龙箭虫高丰度区位于暖流与沿岸流交汇处偏冷水团的一侧。在水温较高的环境下,百陶箭虫高丰度区位于暖流与沿岸流交汇处偏淡水水团的一侧。     

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。     

仿刺参的微卫星标记

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,探讨了东海糠虾类的数量波动、相应的动力学过程及与渔场的关系。结果表明:东海糠虾类秋季丰度最高,均值为10ind.10-2m-3,春季次之(5ind.10-2m-3),夏季最低(1ind.10-2m-3);春季的漂浮囊糠虾(Gastrosaccus pelagicus)、夏季的极小假近糠虾(Pseudanchialina pusilla)、秋季的四刺端糠虾(Doxomysis quadrispinosa)和冬季的中华节糠虾(Siriellasinensis)对糠虾类总丰度变化的贡献较大。冬夏季不同优势种间对总丰度的贡献值较为接近,春秋季则有明显的差异。糠虾类春季和4季总丰度与底层水温线性相关;冬夏季与底层盐度相关;秋季与表层水温和10m层水温相关。东海糠虾类的数量波动,与东海沿岸河流的径流量,特别是长江径流势力消长有密切的联系,也与东海暖流势力从夏季到秋季维持一段时间有密切的关系。秋季糠虾类高分布区出现,对东海北部外海鲐鱼渔场和闽南-台湾浅滩渔场的形成有重要的意义。     

长江口海域浮游软体动物生态特征的季节变化

根据2002-2003年长江口28°00′-2°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软体动物总丰度的平面分布、季节变化、种类组成及优势种的环境适应类型。结果表明,长江口海域浮游软体动物总丰度分别为:春季64.61ind/m3,夏季191.84ind/m3,秋季59.11ind/m3,冬季1.4ind/m3。四季共出现软体动物24种,其中春季8种,夏季21种,秋季10种,冬季2种。马蹄螔螺(Limacina trochiformis)适温较低,是春季主要优势种;明螺(Atlanta peroni)作为暖水种,是夏季主要的优势种;秋季主要优势种为尖笔帽螺(Creseis acicula),适应于较高的水温;强卷螺(Agadina stimpsoniji)适温较低,是冬季的主要优势种。春季浮游软体动物大多聚集在苏北沿岸流和长江径流交汇处或偏沿岸流一侧,夏季在河口咸淡水水团内,秋季的高丰度则主要出现在台湾暖流和长江径流交汇偏暖水的一侧,冬季出现种类较少,低温是其最主要的因素。浮游软体动物作为一种偏大洋性的种类,在外海的数量和种类分布要远高于近海。     

东海浮游十足类优势种环境适应的研究

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,对东海浮游十足类优势种的生态特征进行了研究,探讨这些优势种对环境的适应及与渔场的关系。结果表明:主要优势种有中型莹虾Lucifer intermedius、刷状莹虾Lucifer penicillifer、细螯虾Leptochela gracilis和汉森莹虾Lucifer hanseni。前2个优势种是近海暖水种,细螯虾是广温高盐种,汉森莹虾是外海暖水种。近海暖水种不但平均丰度高,而且优势度和占浮游十足类总丰度的百分比均大于其它优势种。广温高盐优势种具有较高的出现率,细鳌虾丰度不高,但在每个季节、各个海区均有出现。在夏季,低温环境适应力差的暖水种往往有很高的聚集强度。与东海其它类群的浮游动物不同,浮游十足类以夏季丰度最大。就个体数量而言,以近海暖水种个体居多,主要分布在位于东海沿岸河口附近的鱼类产卵场。     

东海浮游桡足类的种类组成及优势种

根据1997-2000年东海23°30′～33°N、118°30′～128°E水域4个季节海洋调查资料,对浮游桡足类种类组成及优势种作了探讨。东海浮游桡足类经鉴定共有226种,呈外海高近海低的分布趋势,夏季(163种)>秋季(152种)>春季(140种)>冬季(123种),4个季节皆出现的有78种。优势种(优势度Y≥0.02的17种,主要有中华哲水蚤(Calanus sinicus)、普通波水蚤(Undinula vulgaris)、精致真刺水蚤(Euchate conicina)和亚强真哲水蚤(Eucalanus subcrassus)等,季节更替明显,在秋、冬季优势种中还新出现了多种中、小型桡足类。北部近海(29°～32°N、125°E以西)春季中华哲水蚤、夏秋季精致真刺水蚤与水温、盐度多元一次逐步回归相关性显著(P<0.05),秋季普通波水蚤与水温、盐度相关性非常显著(P<0.01),春季鳀(Engraulis japonicus)中心渔场(>100kg·h~(-1))分布与中华哲水蚤高密集区(50～100ind·m~(-3))平面分布具有良好的对应关系;春、夏季鳀鱼仔、稚鱼高密度区(≥100ind·net~(-1))与中华哲水蚤高丰度区(50～100ind·m~(-3))相重叠。     

东海海樽类种类组成和多样性

根据1997～2000年在东海海域23°30′～33°N、118°30′～128°E 4个季节海洋调查资料,运用定量、定性方法,探讨东海海樽类(Thaliacea)种类组成、物种数平面分布和多样性变化及与环境的关系.结果显示,东海调查水域共发现浮游海樽类20种,夏季16种,春季12种,秋季11种,冬季9种;季节更替率显示,海樽类物种季节更替,从春季到冬季,是温度的季节变化和暖流势力消长共同作用的结果;从冬季到春季,主要受暖流势力增长的影响.春季海樽类物种数与表温和底盐相关,夏季与10 m水层温度和盐度相关;秋季相关性不明显,冬季与表温相关.东海海樽种类季节特征和地区特征的形成,主要与暖流势力消长有关.双尾纽鳃樽东方亚种(Thalia democratica orientalis)等7个种是东海的常见种,羽环纽鳃樽(Cyclosalpa pinnata)等6个种是次常见种,其余则是稀有种.东海各分海区海樽类多样性指数大多较低,主要是由于优势种具有很强的聚集性,这种种间和各站位之间分配的不均匀性,是多样性指数较低的最主要的原因.     

北部湾西北部饵料浮游动物季节变化及其与鱼卵、仔稚鱼的关系

根据2012年在北部湾西北部广西近海冬、春、夏和秋4个季节的调查资料,探讨了该海域浮游动物总丰度的平面分布、季节变化及鱼卵仔稚鱼的丰度的季节变化,结果表明,调查水域浮游动物的丰度在春夏、秋冬季变化较大,而在冬春与夏秋季变化较小,浮游动物在冬、春、夏、秋四季的平均丰度分别为337.35 ind/m3、280.01 ind/m3、4.32ind/m3和14.78 ind/m3,冬春季明显高于夏秋季,浮游动物数量高峰季比东海提前了一个季节。冬春两季,浮游动物的数量分布特征相近,在湾内和沿岸水域数量高于近海水域。相反,在夏秋季,丰度在近海水域明显高于沿岸及湾内水域。浮游动物在各季节不同的分布特征与该海域沿岸水、外海水和混合水的季节性变化有关,优势种经历了由春季的沿岸暖温种到夏季和秋季的外海暖水种到冬季的沿岸暖水种更替的过程。该海域的主要优势种,冬季为鸟喙尖头溞(Penilia avirostris),春季为中华哲水蚤(Calanus sinicus),夏季和秋季同为肥胖软箭虫(Flaccisagitta enflata),主要优势种类的生态适应性决定了浮游动物总数量的分布特征。鱼卵、仔稚鱼在冬、春、夏、秋季的丰度为6.83 ind/m3、3.09 ind/m3、0.05 ind/m3、0.20 ind/m3,季节变化趋势与浮游动物一致,由高到低依次为冬季、春季、秋季、夏季,两者较强的正相关关系表明,食物饵料充足对鱼卵仔鱼的发育具有促进作用。     

黄、东海春秋季磷虾的数量分布及其与水文环境的关系

依据在2000年10-11月和2001年3-4月两个航次采集的浮游动物样品,对南黄海和东海陆架区磷虾的数量分布进行了研究.共发现9种磷虾,其中以太平洋磷虾(Euphau.sia pacifica)、中华假磷虾(Pseudeuphausia sinica)和宽额假磷虾(Pseudoeuphausia latifrons)占优势.这3个优势种有各自的分布区,分别代表着3个不同的生态类型.太平洋磷虾是最主要的优势种,分布在黄海中央和东海北部的低温高盐水域.其在两个航次中的高丰度(＞1000 ind·m-2)区都有底层冷水(＜12℃)出现.中华假磷虾分布在长江冲淡水及其南北两侧的近岸低盐(24～33.5)水域.秋季航次最高丰度为280 ind·m-2,出现在长江口,盐度仅24～27.宽额假磷虾仅见于秋季航次,分布在黑潮和台湾暖流影响下的高温(＞21℃)高盐(＞33.5)水域,最高丰度为160 ind·m-2.其它6种磷虾数量稀少,除小磷虾(Euphausia nana)外均为暖水性种类.     

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.     

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.     

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.