辽东湾鱼类群落结构的季节变化特征

为探究辽东湾鱼类群落结构的季节变化特征,于2020年5月(春季)、8月(夏季)和10月(秋季)在该海域进行了3个航次的底拖网调查,据此分析辽东湾鱼类种类组成、优势种、多样性和群落空间结构随季节变化的情况,并计算群落季节更替与迁移指数,建立鱼类群落丰度-生物量比较曲线。调查结果显示：辽东湾春、夏、秋3个季节共捕获鱼类58种,其中春季34种、夏季49种、秋季46种;优势种春季为短吻红舌鳎、黄鲫和皮氏叫姑鱼,夏季为矛尾虾虎鱼、短吻红舌鳎、白姑鱼、皮氏叫姑鱼和斑鱼祭,秋季为矛尾虾虎鱼、短吻红舌鳎、六丝钝尾虾虎鱼、黄鲫和皮氏叫姑鱼;鱼类群落的多样性指数为1.34～1.63,丰富度指数为1.44～1.68,均匀度指数为0.60～0.64;辽东湾鱼类可分为3个群落类型,靠近湾顶的北部近岸浅滩水域群落、辽东湾中南部深水区群落和辽东湾湾口深水区群落,其中春季和夏季可分为3个群落组,秋季分为2个群落组;鱼类群落的空间分布在春、夏季与底层温度相关性系数最高(春季R=0.270、夏季R=0.408),在秋季与水深相关系数最高(秋季R=0.376);丰度-生物量比较曲线结果显示,辽东湾鱼类丰度优势度曲线均位于生...     

辽东湾6月鱼类的种类组成及空间分布

利用2007年6月和2008年6月的底拖网调查数据,采用聚类分析和相对重要性指数,分析了辽东湾鱼类群落的种类组成及空间分布特征。结果表明,调查共计捕获鱼类24种,隶属于5目22科24属。2007年优势种为小黄鱼(Larimichthys polyactis)和矛尾鰕虎鱼(Chaeturichthys stigmatias),2008年为小黄鱼和短吻红舌鳎(Cynoglossus joyneri),小黄鱼在两个年份均占据第一优势地位。聚类分析和SIMPER分析表明,2007年6月鱼类群落在空间上可分为3组,对组间相异性贡献较高的分歧种为小黄鱼、黄鲫(Setipinna taty)、矛尾鰕虎鱼、短吻红舌鳎、叫姑鱼(Johnius belengeri)、方氏云鳚(Enedrias fangi)、长绵鳚(Zoarces elongatus)、大泷六线鱼(Hexagrammos otakii)、许氏平鲉(Sebastes schlegeli)等;2008年6月可分为3个组,对组间相异性贡献较高的分歧种为小黄鱼、黄鲫、短吻红舌鳎、李氏(Repomucenus richardsoni)、矛尾鰕虎鱼、长绵鳚、斑纹狮子鱼(Liparis zonatus)、银鲳(Pampus argenteus)和鲬(Platycephalus indicus)等。聚类结果按照地域空间可分为辽东湾北部、中部和西南部,且两个年度6月均表现为辽东湾北部生物量最高,而多样性最低。辽东湾北部水域邻近河口,是鱼类理想的产卵场和保育场,故6月该区域生物量最高。聚类结果表明辽东湾水域6月鱼类的种类组成相对稳定,鱼类的繁殖栖息习性和辽东湾水域不同区域的环境影响着鱼类的种类组成及其空间分布。     

辽宁省近岸海域的渔业资源结构

根据2006年夏季(7~8月)、冬季(11~12月)和2007年春季(4月)、秋季(10月)共4个航次的底拖网调查资料,对辽宁省近岸海域渔业资源结构进行了初步研究。调查结果表明,辽宁省近岸海域共出现渔业生物101种,其中底层鱼类52种,中上层鱼类8种,甲壳类33种,头足类8种。辽东湾近岸海域和黄海北部近岸海域渔业种类组成相似性较高,总体上JACCARD相似性系数超过50%。优势种分析表明,辽宁省近岸海域优势种季节更替明显,口虾蛄(Oratosguilla oratoria)为辽东湾近岸海域四季共有种,大泷六线鱼(Hexagrammos otakii)为黄海北部近岸海域四季共有种。除夏季外,渔获物以底层鱼类和甲壳类为主,渔获量季节变化上以夏季最高;群落多样性指数(D、H'、J')季节变化上均以秋季最高。与历史数据相比,辽宁省近岸海域渔业生物种类数变化不明显,但中上层鱼类如黄鲫(Setipinna taty)、斑鰶(Konosirus punctatus)、蓝点马鲛(Scomberomorus niphonius)等在群落中的优势地位下降,本地性资源如矛尾虾虎鱼(Chaeturichthys stigmatias)、大泷六线鱼、口虾蛄、日本鼓虾(Alpheus japonicus)等成为主要渔业生物。两个海区近岸海域2006~2007年各季节渔业生物总平均体质量均小于40 g,各季节的更替指数均大于80。多样性指数、季节更替指数和迁移指数分析显示,总体上辽宁省近岸海域渔业生物群落的多样性水平较低,群落稳定性较低。平均体质量的结果表明,渔业生物群落主要由小型个体和大中型的低龄群体组成,与历史数据对比,其小型化的特征明显。     

2010年夏季黄河口及邻近海域鱼类群落多样性

为了解夏季黄河口海域鱼类群落结构现状,根据2010年6月、7月底拖网调查数据对该海域鱼类群落的种类组成、优势种、空间分布、物种多样性和群落相似性进行了研究。结果表明,两次调查共捕获鱼类32种,全部为硬骨鱼类,隶属于7目、21科、32属。6月优势种为矛尾虾虎鱼Chaeturichthys stigmatias、短吻红舌鳎Cynoglossus joyneri和斑尾刺虾虎鱼Acanthogobius ommaturus,7月为矛尾虾虎鱼、斑鱼祭Konosirus punctatus、短吻红舌鳎和斑尾刺虾虎鱼。7月调查鱼类生物量和丰度均较6月大幅增加,分别由3.6 kg/h和459 ind./h增加到44.1 kg/h和6 107 ind./h,生物量在每个站位均有所增加,且在整个调查海域分布较为均匀。两次调查鱼类群落的生物量优势度曲线、丰度优势度曲线均接近。7月鱼类群落的丰富度指数（D）、多样性指数（H′）和均匀度指数（J′）均较6月有所下降。聚类分析和NMDS排序结果表明,6月调查站位和7月调查站位各自聚为一组。两次调查鱼类群落相似性较高,Jaccard种类相似性系数为56.3%,根据生物量计算的Bray-Curtis相似性系数为43.1%。与历史数据相比,黄河口鱼类种类数呈下降趋势,优势种类也发生了明显改变,生物量在各月间的分布也有所不同,本次调查7月黄河口海域鱼类资源密度明显高于6月,而20世纪80年代调查数据则恰相反,6月鱼类资源密度高于7月。     

海州湾及其邻近海域鱼类群落结构冗余度

过度捕捞、环境污染等人类活动以及气候变化等影响着海洋鱼类群落动态及其稳定性。为深入研究海州湾海域鱼类群落结构及其变化,根据2011年、2013—2016年春、秋两季在该海域进行的渔业资源与环境调查数据,应用多元统计分析和结构冗余度分析方法,研究了海州湾海域春、秋季鱼类群落结构冗余度。结果显示,海州湾及邻近海域春、秋季鱼类均可划分为南北两个群落。春季北部群落的典型种包括方氏云鳚、细纹狮子鱼、黄鮟鱇和大泷六线鱼;南部群落的典型种为小黄鱼、短吻红舌鳎、方氏云鳚和星康吉鳗。秋季北部群落的典型种为棘绿鳍鱼、长蛇鲻和星康吉鳗;南部群落典型种包括短吻红舌鳎、棘头梅童鱼、鮸、矛尾虾虎鱼、小黄鱼和皮氏叫姑鱼。春、秋季鱼类群落响应单元数均为1,群落结构冗余度水平低;响应单元中种类与南、北鱼类群落典型种组成相似,表明海州湾春、秋季鱼类群落空间结构特征主要受方氏云鳚、细纹狮子鱼、小黄鱼、棘绿鳍鱼和长蛇鲻等少数种类决定。决定海州湾及邻近海域鱼类群落结构特征的可替代种类较少,当主要种类受损时,群落结构会发生较大变化,鱼类群落结构稳定性较低。     

山东北部沿海幼鱼种类组成特征的研究

2008年5月—2009年9月通过双船拖网采样,对山东北部沿海28个站位进行了调查,分析研究了该海域的幼鱼种类组成及优势种。调查结果表明,该海域共出现幼鱼75种,属14目41科65属,以底层鱼类为主要组成,占总种类数的78.67%;优势种有鳀鱼、方氏云鳚、玉筋鱼、黄鲫、蓝点马鲛、小黄鱼、矛尾刺鱼叚虎鱼等;幼鱼种类组成具有显著的季节变化,但年间变化较小。     

莱州湾东部海域底层游泳动物群落结构特征及其季节变化

为了解莱州湾东部海域底层游泳动物的群落结构特征及季节变化规律,基于2020—2021年在该海域开展的秋季和冬季底拖网调查结果,利用物种相似性指数(J)、相对重要性指数(IRI)、聚类分析(Cluster)、非度量多维标度分析(nMDS)、生态位宽度和重叠度指数以及食物网拓扑结构网络分析等方法,探究了该水域内底层游泳动物的群落结构特征及其季节变化趋势。结果显示,秋季、冬季分别捕获底层游泳动物47种、40种,秋季优势种包括短吻红舌鳎(Cynoglossus joyeri)、口虾蛄(Oratosquilla oratoria)、矛尾虾虎鱼(Chaeturichthys stigmatias)、鹰爪虾(Trachypenaeus curvirostris)、日本枪乌贼(Loligo japonica)和三疣梭子蟹(Portunus trituberculatus)6种,冬季优势种包括矛尾虾虎鱼、绯(Callionymus beniteguri)和日本褐虾(Crangon hakodatei)3种,底层游泳动物种类组成和优势种季节更替较为明显;底层游泳动物群落分组在相似性49%的基础上极为显著(...     

崂山湾春季鱼类群落的摄食生态及其主要种类

崂山湾位于黄海的胶州湾和丁字湾之间,海湾开阔,是当前增殖放流的重点海域。根据2014年5月在崂山湾海域进行的底拖网调查,分析了该海域春季鱼类群落的种类组成和摄食生态。结果表明,崂山湾春季鱼类群落共32种鱼类,隶属8目,21科,30属;以鲈形目(Perciformes)的虾虎鱼科(Gobiidae)和石首鱼科(Sciaenidae)种类最多;优势种有皮氏叫姑鱼(Johnius belengerii)、短吻红舌鳎(Cynoglossus joyneri)和矛尾虾虎鱼(Chaeturichthys stigmatias),主要种有大泷六线鱼(Hexagrammos otakii)、斑鰶(Clupanodon punctatus)、赤鼻棱鳀(Thrissa kammalensis)、丝虾虎鱼(Cryptocentrus filifer)、方氏云鳚(Enedrias fangi)和银鲳(Pampus argenteus)。崂山湾春季鱼类群落的种类丰富度指数R为3.19,多样性指数H′为2.34;均匀度指数J′为0.68。胃含物分析结果表明,春季崂山湾生态系统鱼类群落的平均营养级为3.52;主要包括了浮游动物食性、杂食性和底栖动物食性3种食性类型,以底栖动物食性鱼类为主。在当前捕捞、气候变化和人类活动等多重压力下,海湾生态系统承受了巨大的压力,针对不同的海湾生态系统进行基础调研,可为制订相应的增殖放流、渔业保护和管理策略提供重要科学依据。     

鸭绿江河口区鱼虾群落研究

1997－1998年在鸭绿江口设4个测站,双月1次捕取样品,进行鱼虾群落研究。渔获66种水生动物,其中鱼类48种、甲壳类11种、其他动物7种。出现频率最高的前5种为斑尾复虾虎鱼、拟棒鞭水虱、亚洲公鱼、脊尾白虾和纹缟虾虎鱼。数量比例最高的前5种优势种为拟棒鞭水虱（31．82％）、糠虾（25．44％）、中国毛虾（21．21％）、斑尾复虾虎鱼（17．35％）和亚洲公鱼（0．5％）。各站生物量指数和物种丰度分别变化于3．83－33139．59和0．34－2528．24。群落物种的多样性指数（H')变化于0．291－2．889。优势度指数（C1）0．155－0．914,均匀度指数（J')0．113－0．970。群落间相似性系数（Cs)2－3站最高（平均0．649）,1－4站最低（平均0．245）。群落物种种类和数量分布与季节和生态条件密切有关。     

渤海游泳动物群落结构季节变动

基于2015年5月(春季)、8月(夏季)和2016年1月(冬季)3个季节的渤海游泳动物底拖网调查数据，分析游泳动物群落结构的季节变动。调查结果显示，调查共捕获96种游泳动物，其中鱼类55种、甲壳类37种、头足类4种。各季节优势种物种数为2～5种(相对重要性指数大于500),春季优势种为口虾蛄和脊腹褐虾，夏季优势种为鳀、口虾蛄、矛尾虾虎鱼、枪乌贼和葛氏长臂虾，冬季优势种为脊腹褐虾、矛尾虾虎鱼、葛氏长臂虾、日本鼓虾和斑尾刺虾虎鱼。游泳动物相对丰度在春季最小，为244尾/h,夏季最大，为11 391尾/h;相对生物量在春季最小，为1.56 kg/h,夏季最大，为38.57 kg/h。从春季到冬季，渔获物相对丰度和相对生物量呈先升后降的趋势。物种丰富度指数为3.61～4.99,春季最高，冬季最低；香农-维纳多样性指数为1.83～2.40,冬季最低，春季最高；物种均匀度指数为0.49～0.59,冬季最低，春季最高。聚类分析和多维标度分析表明，渤海各海域游泳动物群落结构相似性并无明显季节变动。相似性百分比分析表明，渤海春、夏、冬季游泳动物群落结构的季节差异主要由鳀、枪乌贼和口虾蛄资源量季节变动所致...     

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.     

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.     

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.