卵形鲳鲹的早期胚胎发育

对人工繁殖的卵形鲳鳆（Trachinotus ovatus）受精卵的胚胎发育过程进行了连续观察。受精卵由人工养殖的性成熟亲鱼，经人工催产、自然产卵受精获得。卵形鲳鲮的成熟卵呈圆形，平均卵径为967．8μm。受精卵在水温18～21℃、盐度31的条件下，胚胎发育历时41h27min后孵出仔鱼。胚胎发育为盘状卵裂，胚体后期的发育速度较快；仔鱼脱膜孵化的速度非常快，基本上在1min内就可以完成。初孵仔鱼平均全长为1．548mm，卵黄囊较大。     

暗纹东方鲀胚胎发育的观察

采用连续观察法对暗纹东方鲀(Takifugu Obscurus)人工授精的受精卵的发育进行观察,详细记录了暗纹东方鲀胚胎发育各阶段的形态特征。结果显示:经人工催产所获得的暗纹东方鲀受精卵为圆形,鹅黄色且透明,平均卵径为1.118~1.274 mm,受精卵在水温21℃±0.5℃下,受精3h10min后开始第1次卵裂,受精后40 h30 min开始形成器官,受精后131 h 15 min开始孵出仔鱼。刚孵出的仔鱼全长(2.550±0.675)mm,肌节26~28对,卵黄囊大而侧扁,长径为(1.014±0.075)mm,短径为(0.904±0.095)mm。整个胚胎发育过程可划分为33个时期。     

线纹尖塘鳢胚胎和前期仔鱼发育的初步研究

连续观察了线纹尖塘鳢(Oxyeleotrislineolatus)自然产卵受精的胚胎和前期仔鱼各发育阶段的形态特征。在室温28～29℃下,线纹尖塘鳢的胚胎发育历时70h完成,仔鱼孵化出膜。胚胎发育可分为受精卵、卵裂期、囊胚期、原肠期、神经胚期、器官形成期、肌肉效应期和孵化出膜期8个连续的典型发育期。胚后发育以卵黄囊的消失为依据,划分为前期仔鱼。     

星突江鲽胚胎发育的研究

对人工干法授精、微量充气孵化条件下星突江鲽的胚胎发育进行了研究。星突江鲽受精卵为分离的球形浮性卵，无油球、卵膜薄、光滑且透明，具弹性。吸水前卵径为0．66～0．70mm，吸水后为0．91～1．06mm。根据胚胎发育的外部形态及典型特征将星突江鲽胚胎发育过程划分为卵裂期、囊胚期、原肠期、神经胚期、胚孔关闭、眼泡和肌节形成、尾芽形成、晶体出现、听囊出现、出膜前期和出膜期11个连续的典型时期。在11±0．5℃水温下，受精卵经过101h仔鱼脱膜孵出。初孵仔鱼全长2．3～2．5mm，卵黄囊长径1．075～1．25mm，短径0．60～0．675mm。     

澳洲线纹尖塘鳢人工繁殖技术初报

澳洲线纹尖塘鳢为多次产卵型鱼类，具筑巢产卵习性，人工繁殖需设置人工鱼巢。培育二冬龄鱼作亲鱼，进入繁殖期时平均性腺成熟系数4．02％，相对怀卵量451粒／g。2003年4～5月进行繁殖试验，共计获卵2365万粒；受精率95．4％，获受精卵225．6万粒；经3～5d孵化，孵出鱼化199．7万尾，平均孵化率88．5％。实现了澳洲线纹尖塘鳢鱼苗规模化繁殖。     

葛氏鲈塘鳢胚胎发育初步观察

2011年5月～6月对葛氏鲈塘鳢的胚胎发育进行了初步观察和研究,两条雌鱼共产卵3937粒,孵出仔鱼2890尾,孵化率为73.4%;从受精卵到仔鱼孵出经历时间平均为127h20min,观察葛氏鲈塘鳢胚胎发育可分为受精卵、胚盘形成、卵裂期、囊胚期、原肠期、神经胚期、尾芽期、出膜前期和出膜期九个阶段25个时期。     

红头丽体鱼×红魔丽体鱼杂交子一代胚胎发育及仔鱼形态学观察

对红头丽体鱼[Cichlasoma synspilum（♀）]×红魔丽体鱼[C. citrinellum（♂）]杂交子一代（F1）（俗称“血鹦鹉”）的胚胎及仔鱼形态发育进行观察,描述了各发育时期的发育时序和形态特征。平均受精率为（91.33±3.06）％,平均孵化率为（91.67±2.08）％;血鹦鹉的受精卵呈椭圆球形,黏性,有浅黄、白灰和红褐3种颜色,无油球,平均卵长径为（1.89±0.04）mm;发育过程可分为6个阶段：受精卵阶段、卵裂阶段、原肠期、神经胚期、器官形成期和孵出期,并进一步分为28个发育分期;在水温（30±0.5）℃下历时约52 h 36 min 完成孵化。初孵仔鱼全长（3.71±0.05）mm,卵黄长径为（1.74±0.09）mm,短径为（1.25±0.07）mm,于第3天开始摄食轮虫,孵出后第5天卵黄囊完全消失。第13天全长（11.86±1.02）mm,各鳍条基本形成,进入稚鱼期。     

泰山赤鳞鱼的胚胎发育和仔鱼发育

试验结果表明:泰山赤鳞鱼产卵时间在4~5月,自然产卵水温为18~26℃,产卵于水底细沙中,分散产卵。卵呈弱粘性,金黄色,属沉性卵,平均卵径2.5 mm。在水温18~22℃条件下,胚胎从受精到孵化出膜历时66 h,经过了胚盘形成期、卵裂期、囊胚期、原肠胚期、神经胚期、器官分化期6个主要阶段。初孵仔鱼全长6.0~6.5 mm。卵黄囊前部膨大成球形,约占鱼体整个长度的1/3;后端为均匀的棒状。仔鱼孵出到消化道完全形成约经历136 h。     

月鳢全人工繁殖试验

人工繁殖的月鳢茁种在池塘饲养至亲鱼，并进行亲鱼配对方式对比、饵料种类、孵化方式比较等试验，共配对亲鱼551对次，产卵总量51、4万粒，受精卵31．8万粒，孵出仔鱼27．3万尾，出苗20．2万尾，规格34～52mm；平均受精率61．84％，平均孵化率85．79％，平均出苗率74．14％。     

光唇裂腹鱼胚胎发育与仔鱼早期发育的研究

对人工干法授精的光唇裂腹鱼（Schizothorax lissolabiatus ）胚胎发育和仔鱼早期发育进行观察,描述了从受精卵到卵黄囊期仔鱼发育时期的时序和形态特征。光唇裂腹鱼的成熟卵近似于圆球形,呈金黄色,卵径为（2.2±0.13）mm;受精后12min卵膜吸水膨胀,卵膜径达（3.2±0.21）mm。水温在15-17℃的条件下,孵化时间为174.28h。初孵仔鱼全长为8.5mm,6日龄仔鱼初次摄食丰年虫,进入混合营养期。     

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.