沙湖叶绿素a的时空分布特征及其与环境因子的关系

为探究沙湖水体叶绿素a的时空分布特征及其与水环境因子关系,2015-2017年冬季(1月)、春季(4月)、夏季(7月)、秋季(10月)对沙湖水体叶绿素a含量和常规水环境因子进行采样与检测,分析沙湖叶绿素a含量与环境因子之间的相关性,通过逐步回归法和通径分析探讨了时空性变化对叶绿素a含量的影响。结果表明,沙湖叶绿素a季节变化明显,夏季最高,冬春两季相对较低,最大值出现在2017年7月(夏季),最小值出现在2015年4月(春季),2017年叶绿素a含量最高,年均值为18.94μg/L,空间分布也存在明显差异。相关分析表明,总磷(TP)、化学需氧量(COD_(Cr))、五日生化需氧量(BOD_5)和透明度(SD)是影响沙湖叶绿素a含量的主要环境因子;逐步回归分析表明,不同季节、不同采样点影响沙湖叶绿素a含量的环境因子存在差异,有机污染物与氮磷营养盐是主要的影响因子;通径分析表明,化学需氧量和总磷的总决定系数(d_(ij))分别为0.379和0.373,是影响沙湖叶绿素a含量最主要的两个环境因子;其中总磷对沙湖叶绿素a含量的直接作用较大,是对叶绿素a起决定性作用的限定性营养盐。     

南海湖营养盐季节特征及其与叶绿素a的相关性研究

为了解包头市南海湖水体水质状况及富营养化趋势，于2017年4月-2018年3月，在南海湖中选取20个采样点，对水体中叶绿素a含量及主要营养盐进行测定，并对叶绿素a和营养盐含量进行相关系分析。结果表明：南海湖水体总氮和总磷指标均超过了地表水Ⅴ类标准。南海湖氮磷营养盐存在着时空差异，总氮和氨氮随季节变化明显，其含量均呈现冬季>秋季>夏季>春季；总磷的含量主要表现为秋季最高，春季最低；硝态氮的含量在四个季节差异不大。空间上各营养盐均呈现东部、北部高，西部、南部低的趋势。水体中叶绿素a含量的变化区间为21.94~40.92μg·L-1，时间上呈现秋季>夏季>春季>冬季。空间上呈现东北高、西南低的趋势，与氮磷营养盐的分布趋势相同。叶绿素a在四个季节中与总氮，氨氮，总磷均呈现显著正相关（P＜0.05）。     

泼河水库叶绿素a的分布特征与环境因子的关系

本实验在2012年9月~2013年9月期间,每季节采样一次,测定泼河水库叶绿素a(chl.a)的浓度,分析泼河水库叶绿素a的分布特征及其与总氮(TN)及总磷(TP)等环境因子的相关性。结果发现,泼河水库叶绿素a浓度的季节分布由高至低为夏季春季秋季冬季;空间分布为春季和夏季河流入库口叶绿素a的浓度高于其他水域;因子相关性分析表明,春季和夏季泼河水库叶绿素a浓度与水体中总磷的浓度相关,其中夏季相关性极其显著。     

三峡水库试验性蓄水后小江沿岸水质研究

根据2010年3月－12月对三峡水库小江沿岸水体的水质监测数据,分析总氮、总磷、化学需氧量和叶绿素a等水质因子的时空变化规律,以及叶绿素a与水质因子之间的相互关系,评价水体富营养化水平。结果表明：总氮、总磷、化学需氧量和叶绿素 a含量分别为1.980±0.119mg/L、0.114±0.018mg/L、9.520±1.748 mg/L和23.342±8.810 mg/L,小江沿岸水体呈现中度富营养化水平。叶绿素a与水质因子间的相关关系分析发现,叶绿素a含量与温度、pH、溶解氧、亚硝酸氮和化学需氧量显著相关,与总氮、总磷不具有显著相关性。这说明小江沿岸水体叶绿素a含量与总营养盐无关,而主要与水体所含的有机质含量有关。     

华阳河湖群叶绿素a浓度的季节动态和空间分布

为了探究华阳河湖群叶绿素a浓度的季节动态与空间分布规律,2016年4月(春季)、7月(夏季)、10月(秋季)和2017年1月(冬季),对华阳河湖群叶绿素a的季节动态及环境因子进行调查,在龙感湖、黄大湖和泊湖分别设置9个(S_1～S_9)、8个(S_(10)～S_(17))和7个(S_(18)～S_(24))采样点,共计24个采样点;通过分层聚类法分析叶绿素a的时空分布特征,并运用主成分分析法探讨了华阳河湖群叶绿素a与环境因子的关系。结果显示,华阳河湖群水体叶绿素a浓度呈现明显的时空分布特征,叶绿素a年均值为7.18μg/L,变化范围0.27～66.61μg/L,最大值出现在2016年10月(秋季),最小值出现在2017年1月(冬季);叶绿素a浓度的季节变化呈现夏、秋季较高,春、冬季较低的动态特征。在空间变化上,叶绿素a浓度在龙感湖最高,其次是泊湖,黄大湖最低。运用分层聚类分析法将华阳河湖群的叶绿素a的时空特征分为三类;主成分分析表明,水体中营养盐是影响叶绿素a季节动态和空间分布的主要环境因子,总氮在3个湖泊中与叶绿素a显著正相关,总磷与叶绿素a在泊湖和黄大湖呈负相关,而在龙感湖呈正相关。研究表明,越冬水鸟的排泄物对叶绿素a的时空分布有重要影响。     

鹤地水库叶绿素a时空分布特征及其与环境因子的关系

为全面了解鹤地水库水体富营养变化趋势及导致水体富营养化的环境因子,于2010-2015年2月、5月、8月和11月,对鹤地水库叶绿素a含量及主要环境因子进行测定,分析鹤地水库叶绿素a含量的时空分布特征,运用逐步回归分析方法探讨鹤地水库叶绿素a和环境因子之间的相关关系,建立逐步回归方程,并运用主成分分析法对影响鹤地水库水质的主要环境因子进行了分析。结果表明,鹤地水库叶绿素a含量在0.8~44.5μg/L,该水库处于富营养化水平;在时空分布上,叶绿素a含量季节变化表现为枯水期最低、平水期其次、丰水期相对较高;空间变化表现为河流区浓度较高,过渡区和湖泊区较低。运用逐步回归分析法建立的全库区叶绿素a回归方程为:Y_(Chl-a)=7.690X_(COD_(Mn))-32.587 X_(TP)-8.689(P0.001),影响鹤地水库叶绿素a含量的显著影响因子为高锰酸盐指数和总磷,总磷可能为浮游植物生长的限制性因子。主成分分析结果表明,影响水库水质的主要环境因子有透明度、氨氮、总磷、总氮和硝态氮。     

黑河干流浮游动物与水环境因子关系的多元分析

为探明黑河干流浮游动物与水环境因子之间的关系,分别于2015年4月、7月和12月测定黑河干流浮游动物密度、生物量与水环境因子,应用多元逐步回归分析、通径分析和典范对应分析方法进行研究。结果表明：黑河干游浮游动物种类以轮虫等小型个体为主,其密度、生物量及种群分布受到水环境因子的共同作用,各断面水环境因子的差异是浮游动物数量变动及分布情况不同的主要原因。上游浮游动物数量变动受水体叶绿素a含量和溶氧影响,高锰酸盐指数和总磷决定浮游动物的分布；中游浮游动物数量变动受叶绿素a含量和透明度制约,其分布与pH、溶氧、电导率、总磷、高锰酸盐指数、叶绿素a密切相关; 影响下游浮游动物密度的主要因子是叶绿素a含量、溶氧、总磷和电导率,生物量则与叶绿素a含量、总氮和电导率相关,总磷和溶氧共同决定下游浮游动物的分布。     

星海湖浮游植物群落结构及与水环境因子的关系

于2017年春(4月)、夏(7月)、秋(10月)和冬季(1月)测定星海湖的浮游植物密度、生物量以及叶绿素a和水温(WT)、pH、溶解氧(DO)、化学需氧量(COD_(Cr))、氨氮(NH_3-N)、总氮(TN)、总磷(TP)、高锰酸盐指数(COD_(Mn))、透明度(SD)、叶绿素(chl.a)、生化需氧量(BOD_5)等水质指标,采用相关性分析、逐步回归分析、通径分析和灰关联法分析星海湖浮游植物与水环境因子之间的关系以及影响浮游植物的最主要水环境因子。结果表明,星海湖水体基本为绿-硅-蓝藻中污染型。星海湖中浮游植物指标与大多数水环境因子之间呈极显著的正相关。浮游植物生物量与TN、BOD_5之间有显著的线性回归关系;浮游植物密度与pH、SD、DO、COD_(Cr)、TN、BOD_5之间有显著的线性回归关系;叶绿素a与WT、pH、COD_(Mn)、NH_3-N、TN之间有显著的线性回归关系;氮营养盐对星海湖浮游植物影响最大。     

三峡水库小江回水区叶绿素a与环境因子时空变化

于2013年1-12月在小江水华暴发的敏感区域高阳断面开展了水文、营养盐、叶绿素a等指标长期、定点监测,分析库湾水体叶绿素a及环境因子的时空变化特征及其相互关系。结果表明高阳断面水体在1月、10-12月处于混合状态,3-8月则处于弱分层到稳定分层状态。水体在混合状态时各理化因子、营养盐及叶绿素a分层变化不显著；而处于分层状态时,各层水体氮磷营养盐呈现较显著差异,时间分布上冬季略高于夏季,干流倒灌对高阳断面营养盐的季节分布影响显著。叶绿素a浓度呈现明显的夏季高、冬季低的趋势,水体分层对叶绿素a垂向分布影响显著,当水体处于分层状态时,表层叶绿素浓度明显高于中、底层。高阳断面各层水体叶绿素a浓度与硝氮和可溶性磷酸盐呈显著负相关,表明营养盐是小江高阳叶绿素变化的限制因素。表层水体叶绿素a与硝氮、磷酸盐、溶解氧、透明度、水温、表底温差等呈显著相关(P<0.01),表明表层叶绿素a与环境因子相关性较强；中层叶绿素a与硝氮、总氮、总磷、磷酸盐、水温、透明度、水深、水体稳定系数等呈显著相关(P<0.01),表明水体的扰动是影响中层水体叶绿素a增长的关键因素之一；底层水体叶绿素a与硝氮(P<0.01)、磷酸盐(P<0.05)、水深(P<0.05)呈显著相关。     

乌溪江水库富营养化程度及其影响因子时空分布探讨

为了解乌溪江水库主要水质指标的时空分布特征,探究其营养化程度的变化趋势,2019-2020年,对丽水市乌溪江水库的7个采样点（S1-S7）的水温、pH、总氮、总磷、叶绿素a等理化因子进行了监测。分析对比了综合营养指数和理化因子等关键指标在不同时期的分布特征。结果表明,乌溪江水库的营养盐浓度呈现出春夏高秋冬低、从上游（S1）至下游（S7）逐渐下降的趋势,平均综合营养指数也从47.1（S1）下降到32.5（S7）,整体上属于中营养化水库。总磷浓度在0.002-0.040mg/L间,平均值为0.012mg/L;总氮浓度在0.412-2.826mg/L间,氮的主要赋存形式为硝酸盐。叶绿素a含量均值为3.77 ug/L,河流区的叶绿素a含量显著高于下游的过渡区和湖泊区。分析表明：汛期地表径流带来的富营养化压力最大,同时也是氮磷等外源性营养盐输入水体的主要途径;WD、pH、TP和叶绿素a含量中等程度相关,水库生态系统具备很强的净化能力。但近年来富营养化程度加剧。     

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.