新疆博斯腾湖轮虫群落季节动态及其影响因子

为探索内陆干旱区湖泊轮虫群落的季节变化与环境因子的关系,对博斯腾湖17个站位的轮虫及其主要环境因子进行了4次采样调查,探究其群落结构特征及其演替规律,并利用典范对应分析研究了博斯腾湖轮虫物种和多样性对环境变量的响应,为博斯腾湖水环境评价与保护、渔业资源合理利用及可持续发展提供背景资料。结果表明:(1)调查期间共鉴定轮虫41种(属),各季节优势种类共8种。夏季优势种类主要为胶鞘轮虫(Collotheca sp.)和针簇多肢轮虫(Polyarthra trigla),低温期的优势种群为矩形龟甲轮虫(Keratella cochlearis);(2)博斯腾湖轮虫密度为0.2~174.0个/L,总平均密度为25.5个/L,生长繁盛期主要出现在春、夏季且受工农业等人为影响较多的浅水区,秋、冬季密度显著降低;(3)水体综合营养指数(TLI)的波动(31.15~46.28)对博斯腾湖轮虫密度的影响不大;(4)水温是影响轮虫群落最重要的环境因子,水温升高、轮虫多样性增加。轮虫种类分布对p H变量的响应较敏感,p H较高时,壶状臂尾轮虫(Brachionus urceus)形成优势,p H较低时,裂痕龟纹轮虫(Anuraeopsis fissa)和长三肢轮虫(Filinia longiseta)形成优势。随着总有机碳预测值的增加,轮虫群落多样性呈增加趋势。     

Evaluation of nutritional and environmental variables during early larval culture of pigfish Orthopristis chrysoptera (Linnaeus)

Pigfish (Orthopristis chrysoptera Linnaeus) are a commonly used baitfish in the southeastern United States. Aquaculture methods for broodfish spawning and juvenile grow‐out have been developed but there is still a paucity of information regarding larval culture methods. Five, short duration (10 days) experiments were conducted to determine effective strategies to yield high larval survival and growth during early development. Experiment one examined the rotifer enrichments Ori‐Green, DHA Protein Selco, and AlgaMac 3050 as well as a non‐enriched control along with corresponding fatty acid levels in the enriched rotifers and pigfish larvae. Experiment two evaluated three, once daily feeding frequencies of either 5, 10 or 20 rotifers mL^?1. Experiment three compared feeding 20 rotifers mL^?1 once daily to feeding 5 rotifers mL^?1 twice daily. Experiment four examined four different larval stocking densities: 50, 75, 100, or 125 larvae L^?1. Experiment five examined green water strategies using either live Tahitian strain Isochrysis galbana (Parke) or Nannochloropsis oculata (Hibberd) paste at either 250 000 or 500 000 cells mL^?1 as well as a clear water control. Results indicated rotifer enrichment with DHA Protein Selco and green water application using live T‐ISO at 500 000 cells mL^?1 had the highest survival of pigfish during early stages of larval culture. A once daily rotifer feeding regime of 20 rotifers mL^?1 and stocking density of 50 larvae L^?1 also improved survival. These results provide producers with methods to improve efficiency for pigfish larval culture and provide researchers with new foundational data, such as potential fatty acid requirements.     

Natural zooplankton as larval feed in intensive rearing systems for juvenile production of Atlantic cod (Gadus morhua L.)

The growth potential of cod larvae is not fully achieved when rotifers (Brachionus spp.) are used as live feed. In this experiment, we studied the effect of natural zooplankton (mainly copepods) on the growth of cod (Gadus morhua L.) larvae reared in intensive systems. Using a growth model developed for cod larvae, the growth rates observed could be evaluated and compared with growth rates reported previously. The cod larvae showed optimal growth rates until age 19 days post hatch (DPH) when they reached 9.77 ± 0.25 mm standard length (SL). Early weaning (20–25 DPH) resulted in significantly longer larvae at age 30 DPH compared with late weaning (25–32 DPH); however, in this period, the zooplankton concentrations were low. The experimental larvae showed considerably higher growth rates compared with rotifer (Brachionus spp.)‐reared cod larvae in previous experiments. The nutritional composition of cod larvae was analysed and compared with published results on rotifer‐reared larvae. The levels of iodine, manganese, selenium and n‐3 PUFA were considerably higher in larvae fed copepods compared with larvae fed rotifers. The differences in nutritional status may well explain the differences in growth observed between copepod and rotifer‐reared larvae.     

微囊藻水华对淡水浮游动物轮虫和枝角类影响的研究进展

微囊藻是最为常见也是研究最多的水华蓝藻之一。有关微囊藻对浮游动物尤其是对枝角类溢属动物的影响,目前国内外已广泛报道。总体而言,产毒微囊藻对浮游动物具有明显的负面影响,但不同浮游动物对这种影响表现出不同的响应。关于微囊藻对浮游动物的毒性效应及影响,存在着一些相互冲突的观点并有很多种解释。本文就微囊藻水华对枝角类和轮虫的摄食、生长、繁殖和种间竞争的影响进行了综述,同时对由此引发的适应性特征进行了概述,旨在总结前人的研究成果,为今后的研究提供参考依据。[中国水产科学,2008,15（2）：367-375]     

Effect of larval and prey density, prey dose and light conditions on first feeding common dentex (Dentex dentex L.) larvae

Initial larval stocking density, prey density, daily prey ration and light conditions (light intensity and photoperiod) were tested for common dentex larval rearing under experimental conditions. Experiments continued until the first peak of larval mortality. The best results in larval survival were obtained with an initial stocking density of between 10 and 40 larvae L^?1, fed with at least 10 rotifers mL^?1, maintaining ratios of 500–1000 rotifers larva^?1, with one or two adjustments of prey density per day. The use of more than 2000 rotifers larva^?1 or three daily adjustments of live prey density had negative effects on larval survival. The best light conditions for common dentex larval rearing were found using a photoperiod of 24 h L:0 h D and an intensity of at least 3.4 μmol m^?2 s^?1.     

Marking live feeds with inert metal oxides for fish larvae feeding and nutrition studies

Yttrium oxide (Y₂O₃), ytterbium oxide (Yb₂O₃), lanthanum oxide (La₂O₃) and dysprosium oxide (Dy₂O₃) were evaluated as potential live feed markers for feeding and nutrition studies with fish larvae, by determining the uptake and depletion of markers over time in two trials, and quantifying ingestion of Y₂O₃‐marked rotifers (Branchionus plicatilis) by Atlantic cod (Gadus morhua) in a third trial. In the first two trials, Artemia nauplii and rotifers quickly took up markers within 10 min to concentrations useful for nutrition studies (>2% dry weight). There was no significant difference (P>0.05) among temperatures in depletion of markers (10, 15, 20 °C) with Artemia or rotifers. Depletion from rotifers was not significantly different (P>0.05) between 5 and 20 min nor between 5 and 30 min for Artemia when marked at a concentration of 50 mg of marker per litre of seawater. In the second trial, rotifers and Artemia were marked with a higher concentration (250 mg L^?1) and allowed to deplete for a longer time (90 min). In the third trial, visual estimates of Artemia consumed by Atlantic cod larvae were similar to consumption estimates determined by analysis of Y₂O₃‐marked Artemia using inductively coupled plasma optical emission spectroscopy (r²=0.77).     

褶皱臂尾轮虫的敞池增殖

池塘的底泥中蕴藏着丰富的轮虫休眠卵,搅动底泥使其上浮可促进萌发、繁衍形成轮虫种群数量高峰期。高峰期的生物量和持续的时间与水温、食物、pH等诸多因子有关,其中饵料浮游植物的种、量是重要影响因子。在大型浮游植物长期占优势的水体,轮虫种群数量增长极慢。作者还根据轮虫的现存量估算了轮虫池的供饵能力。     

南极大磷虾粉对褶皱臂尾轮虫生长及脂肪酸组成的影响

以活性干酵母培养的褶皱臂尾轮虫(Brachionus plicatilis)为对照,并以南极大磷虾粉对轮虫进行强化,设定轮虫培养液中南极大磷虾粉质量浓度分别为30、50和70 mg/L。分别测定强化12 h和18 h时轮虫的密度、带卵率以及强化后6 h、12 h、18 h轮虫的脂肪酸组成与含量。结果表明,12 h和18 h时,50 mg/L组的轮虫密度急剧升高,并显著高于其他3组,依次表现为50 mg/L组>30 mg/L组>对照组>70 mg/L组。带卵率方面:第12小时和18小时带卵率由高到低依次为50 mg/L组、30 mg/L组、70 mg/L组、对照组(P<0.05)。脂肪酸方面:6 h时,除了70 mg/L组的ARA与对照组、50 mg/L组和70 mg/L组的ω6-系列多不饱和脂肪酸总量(∑ω6-PUFA)与对照组没有显著差异外,其余强化组的ARA、EPA、DHA、ω3-系列多不饱和脂肪酸总量(∑ω3-PUFA)和∑ω6-PUFA都显著高于对照组(P<0.05);尤其是50 mg/L组的DHA和∑ω3-PUFA显著高于其他两个强化组和对照组(P<0.05),含量几乎达到对照组的10倍。12 h和18 h时,所有强化组的ARA、EPA、DHA、∑ω3-PUFA含量都显著高于对照组(P<0.05),而且50 mg/L组的上述脂肪酸含量都是最高的,或者与30 mg/L组和70 mg/L组并列第一。3个强化组的DHA/EPA比值、EPA/ARA比值也显著高于对照组(P<0.05)。结论认为,南极大磷虾粉的强化剂量以50 mg/L为优,强化时间则以12 h和18 h为宜,南极大磷虾粉对褶皱臂尾轮虫具较好的营养强化效果。     

Improvement of rotifer Brachionus plicatilis population growth dynamics with inclusion of Bacillus spp. probiotics

Due to growing interest in bacterial probiotic incorporation within juvenile marine finfish production, multiple commercial products are currently available. The following trial was conducted to test the effect of incorporation of a commercially available Bacillus spp. probiotic blend (EcoAqua) on population growth dynamics of the rotifer Brachionus plicatilis. Incorporation consisted of 0.1 mL L^?1 daily probiotic additions directly to rotifer cultures and 0.1 μL mL^?1 additions to feed mixtures during preparation. Probiotic‐treated cultures’ daily mean populations were found to be significantly greater (P_α(2),4,4 < 0.05) on multiple culture days. This trend was confirmed as significant (P_α(2),1,45 < 0.001) using ancova . Logistic population growth curves fit for each treatment were statistically non‐coincident (P_α(2),5,40 < 0.001). Substantial differences between treatment and control parameter estimates were observed; however, statistical comparisons could not be employed. Population variability was also reduced by probiotic inclusion as evidenced by lack of significant, positive correlation for probiotic daily population standard deviations (r = 0.0022, P = 0.99) and detection of a significant, positive correlation for control absolute value regression residuals (r = 0.50, P = 0.013) with Day of Culture. The tested bacterial probiotic improved rotifer culture population dynamics, suggesting potential production benefits from its utilization.     

Optimization of emulsion properties and enrichment conditions used in live prey enrichment

Five variables relating to the enrichment of live prey were studied using experimental micellar emulsions. Rotifers and Artemia nauplii were enriched for 12 and 24 hrs, respectively, and sampled at several intervals to analyse their fatty acid profile and determine the better time length for enrichment. Two hour and 18 hr were shown to be the most effective in boosting rotifer and nauplii, respectively, with arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids as well as in total lipid content. Three doses of the same emulsion were also used to check which one conferred the best fatty acid profile. In this case, the higher the dose utilized the higher the content of DHA present in the live food. The use of 15 g/Kg–20 g/Kg of egg yolk as emulsifier was proved to be very effective on rotifer boosting, whereas for nauplii, the amount of emulsifier might be reduced. Egg‐derived emulsifiers have been shown to be more effective for rotifer enrichment while for Artemia nauplii, soy lecithin rendered a better fatty acid profile. Finally, live prey lipid composition paralleled that of the oil used in the emulsion formula although rotifers were far more easily enriched than Artemia nauplii especially in DHA but not in EPA or ARA.