不同盐度和饵料藻对牡蛎体内重金属排出率影响的研究

贝类是水产品的主要品种之一，具有营养丰富、风味独特的特点。但研究表明，目前我国已有约20万km^2的近海海域受到污染，海水水质达不到国家一类海水水质标准，重金属对底栖滤食性贝类的污染愈来愈严重，尤其是Cd和Pb超标现象严重，许永安Ⅲ等研究UV法对文蛤、花蛤、缢蛏的净化效果，指出大量降低贝类的重金属含量似乎不可能。陆超华等研究盐度对近江牡蛎体内Pb、cd排出的影响，指出水体盐度的升高有利于近江牡蛎体内残留Pb的排出，而有碍于残留Cd的排出。     

盐度骤降对近江牡蛎和长牡蛎能量收支的影响

采用实验生态学方法，研究了盐度骤降(盐度分别为10、20，自然海水为对照组)对近江牡蛎(Crassostrea ariakensis)和长牡蛎(Crassostrea gigas)生理代谢的影响。结果显示，盐度骤降对长牡蛎和近江牡蛎的耗氧率(OR)、排氨率(NR)、排粪率(FER)均有显著影响(P<0.05)，且2种牡蛎对盐度骤降的响应存在差异。长牡蛎的耗氧率、排氨率、摄食率(IR)和排粪率均在自然海水中最高，低盐对长牡蛎产生不同程度的胁迫。而近江牡蛎在盐度为20时的上述指标显著高于其他盐度处理组。通过测定不同规格牡蛎的代谢率，建立2种牡蛎在不同盐度下的代谢率与规格(湿重)的回归方程，该方程符合幂指数：Y=aWb。通过归一化处理，比较湿重在20 g时，2种牡蛎的能量分配差异。盐度为20时，近江牡蛎的呼吸代谢较强(呼吸能占16.1%)，而长牡蛎在自然海水中呼吸代谢较强(呼吸能占7.8%)，2种牡蛎的呼吸代谢均在盐度为10时较低，其中，长牡蛎呼吸能仅占0.7%。研究表明，盐度骤降对长牡蛎的影响大于近江牡蛎，小幅度的盐度骤降对近江牡蛎的能量代谢有一定的促进作用。本研究从能量代谢角度，探讨了近江牡蛎和长牡蛎对盐度骤变的响应，可为牡蛎礁修复工作和养殖生产过程中的品种选择提供参考。     

广东沿海贝类4种重金属含量分析和评价

根据2007年6～9月对广东沿海4种贝类养殖区90个样品的检测结果，研究了贝类体内重金属的含量和累积，对贝类的质量安全进行评价。结果表明：（1）菲律宾蛤仔Ruditapes philippinarum体内含量大小顺序为铜（Cu）〉镉（Cd）〉铬（Cr）〉铅（Pb），太平洋牡蛎Crassostreagigas和近江牡蛎C．rivularis的大小顺序都是Cu〉Cd〉Pb〉Cr，而翡翠贻贝Pernaviridis的大小顺序则是Cu〉Pb〉Cd〉Cr；（2）菲律宾蛤仔、太平洋牡蛎和翡翠贻贝未受重金属污染，但部分近江牡蛎体中Cd和Cu含量已超过中国农业行业标准“无公害食品：水产品有毒有害物质限量”标准，应该引起重视。     

盐度胁迫对近江牡蛎几种免疫因子的影响

试验分析了盐度从18骤变至3、25、40的第24 小时和第48 小时江牡蛎（Crassostrea hongkongensis）血淋巴超氧化物歧化酶（SOD）、碱性磷酸酶（AKP）、过氧化氢酶（CAT）和溶菌酶（LSZ）的活力变化，旨在研究盐度骤变对相关免疫因子的影响。结果显示，对照组（盐度18）4项免疫因子变化不显著（P＞0.05）。盐度25组AKP、LSZ活力在第24 小时极显著高于对照组（P〈0.01）。盐度3组SOD活力在第24 小时显著高于对照组（P〈0.01），其他酶活力与对照组相比差异不显著。盐度40组SOD活力在第24 小时显著低于对照组（P〈0.01），而LSZ活力在第48 小时急剧下降，极显著低于对照组（P〈0.01），其他酶活力与对照组相比差异不显著。由此可见，盐度骤变对近江牡蛎的免疫活力有明显的刺激作用，且可能在一定范围内能够增强机体免疫力。近江牡蛎对低盐有很强的适应能力，但在高盐胁迫下其免疫活力下降。     

构建近江牡蛎产业带，促进粤西广西沿海水产业发展

广西钦州市茅尾海是全国最大的近江牡蛎采苗基地，每年可生产近江牡蛎种苗1．5亿支（串），其中有部分种苗销往广东湛江、汕头、中山、台山等市及海南省进行养殖。近江牡蛎属滤食性贝类，主要滤食海水中的藻类，从理论上说，它是无公害产品。粤西与广西沿海一衣带水，气候与海洋环境十分相似，而近江牡蛎产品营养丰富，历来是消费者喜爱的食品，因此，构建粤西、广西沿海近江牡蛎产业带，将极大地促进两地渔农民的增收和水产业的发展。     

盐度与pH对3种南方贝类呼吸率和钙化率的影响

测定了近江牡蛎(Crassostrea rivularis)、翡翠贻贝(Perna viridis)和波纹巴非蛤(Paphia undulata)3种南方重要养殖贝类在20、25、30和35共计4个盐度梯度和8.1、7.7、7.3和7.0共计4个pH梯度下的呼吸率和钙化率。结果表明,盐度和pH对3种贝类的呼吸率和钙化率均有显著影响(P0.05);盐度为20~35,近江牡蛎的呼吸率和钙化率均随盐度的升高而降低,而翡翠贻贝和波纹巴非蛤在盐度为20~30时,呼吸率和钙化率随盐度的升高而升高,盐度30~35时,随盐度的升高而下降。pH为8.1~7.0时,3种贝类的呼吸率和钙化率均随着pH的下降而显著性下降(P0.05)。     

混合重金属对翡翠贻贝的积累与排放规律研究

通过对翡翠贻贝（Mytilus edulis）进行混合重金属积累与排放的慢性实验，研究了重金属铅（Ph）、锌（Zn）、铜（Cu）、镍（Ni）、镉（Cd）、铬（Cr）、汞（Hg）和砷（As）的混合溶液在翡翠贻贝体内的积累规律和排放规律。结果表明，翡翠贻贝对Ph、Zn、Cu、M、Cd、Cr、Hg和As的富集和排放规律性较强，在累积实验中，翡翠贻贝体内各种重金属含量随着时间的推移明显呈上升趋势，翡翠贻贝对重金属Pb，Cu，Ni，Cd，Zn、As、Cr和比有较强的累积能力，可很好地指示海水中这些重金属的污染；在排放实验中，翡翠贻贝体内各重金属含量随时间的推移呈下降趋势，但排放曲线都较平缓，表明翡翠贻贝在实验过程中，释放体内重金属较缓慢。     

盐度对白对虾生长和存活的影响

盐度对白对虾生长和存活的影响第一组白对虾（Ｐａｓｅ。。ｈａ－－）仔虾，平均体重回．６ｇ，分别在盐度５、互５、２５、３５和４９的海水中试养３５天，结果是：在盐度５和１５的海水中，仔虾生长最快（每周生长大于Ｚｇ），明显大于较高盐度组试养的仔虾，但盐度５、...     

流沙湾贝类养殖海域环境质量评价

根据2008年5月至2009年2月对流沙湾贝类养殖海域渔业环境综合调查的数据，对海水环境质量的现状进行了分析讨论，综合评价了海水有机污染和营养水平，并对沉积物重金属的累积程度和潜在生态危害进行了评价。结果表明，调查海域盐度、溶解氧（DO）、化学耗氧量（COD）、无机氮（DIN）和活性磷酸盐（PO4^3-）呈季节性变化，其中盐度和DIN的季节变化与该海域季节性降水有关，而DO、COD和PO4^3-的变化与浮游植物和贝类养殖有关。评价结果显示，流沙湾海域水质清洁，海水氮（N）营养盐过剩而磷（P）贫乏，属于P限制型中等富营养化海域；调查海域沉积物中砷（As）和铅（Pb）处于无污染状态，汞（Hg）和镉（Cd）处于轻度污染，铜（cu）在部分区域处于中度污染状态；Ca、Pb、As、锌（Zn）和铬（Cr）的潜在生态危害属于轻微，Hg和Cd的潜在生态危害处于中等强度。     

应用重金属和有机污染物对人体健康的风险评价理论反推牡蛎安全消费量

为了提供牡蛎食用安全性参考信息，文章根据有毒化学物质的人体健康风险评估计算式，提出了牡蛎适宜消费量推算方法；对2007年春季在南海北部沿岸23个海湾采集的近江牡蛎（Crassostrea rivularis）样品，用气相色谱法测定了其中有机氯农药、多氯联苯的含量，用原子吸收分光光度法和原子荧光分光光度法测定了其中重金属的含量，推算了近江牡蛎的适宜消费量。结果能清晰地显示牡蛎采集海域、有毒化学物质种类对应的近江牡蛎软组织日均适宜消费量。     

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.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.