Effects of sample size on numerical estimates of diel prey consumption in a fish population

Numerical data based on stomach content analysis of the zooplanktivorous freshwater fish, Retropinna semoni, were used to examine the effect of fish sample size on mean counts of dominant prey items. Fifty adult R. semoni were collected from throughout the open‐water of Lake Benanee, Australia at each of five times over a diel period. Bootstrapping was used to generate confidence intervals around sample means, and markedly more accurate means were obtained from samples collected in the day than the night. High variation in night samples was the by‐product of a diurnal feeding regime. Traditional sample sizes of 10 to 15 stomachs resulted in reasonable confidence intervals of sample means derived from collections on the first day, corresponding to uniform feeding patterns in the population. However, increased sample sizes were required to describe more complex feeding behaviour on the second day, when a proportion of the population switched to an alternative prey source.     

除草剂百草枯对褶皱臂尾轮虫(Brachionus plicatilis)摄食和实验种群动态的影响

采用实验生态学方法研究了除草剂百草枯对褶皱臂尾轮虫(Brachionus plicatilis)的摄食和种群动态的影响。结果表明,百草枯对褶皱臂尾轮虫的24hLC50为9.17mg/L,对褶皱臂尾轮虫的摄食具有明显的抑制作用。实验浓度下褶皱臂尾轮虫对小球藻的滤水率和摄食率随百草枯浓度的增加先下降后升高。百草枯对褶皱臂尾轮虫种群动态影响显著,使轮虫的胚胎发育时间、繁殖前期和繁殖后期延长,繁殖期和平均寿命缩短,产卵量和繁殖率降低。轮虫的净生殖率和世代时间均低于对照,不同百草枯浓度下轮虫能够维持一定的种群增长。     

The diel vertical migration of the sound-scattering layer in the Yellow Sea Bottom Cold Water of the southeastern Yellow Sea：focus on its relationship with a temperature structure

Using the hydroacoustic method with a 200 kHz scientific echo sounding system,the diel vertical migration(DVM) of the sound-scattering layer(SSL) in the Yellow Sea Bottom Cold Water(YSBCW) of the southeastern Yellow Sea was studied in April(spring) and August(summer) of 2010 and 2011.For each survey,13–27 hours of acoustic data were continuously collected at a stationary station.The acoustic volume scattering strength(Sv) data were analyzed with temperature profile data.In the spring of both 2010 and 2011,the SSL clearly showed the vertical migration throughout the entire water column,moving from the surface layer at night to near the bottom during the day.Conductivity,temperature,and depth data indicated that the entire water column was well mixed with low temperature of about 8 C.However,the SSL showed different patterns in the summers of 2010 and 2011.In the summer of 2010(28 C at the surface),the SSL migrated to near the bottom during the day,but there were two SSLs above and below the thermocline at depth of 10–30 m at night.In the summer of 2011(20 C at the surface),the SSL extended throughout the entire water column at night,possibly owing to an abrupt change in sea weather conditions caused by the passage of a Typhoon Muifa over the study area.It was concluded that the DVM patterns in summer in the YSBCW area may be greatly influenced by a strengthened or weakened thermocline.     

基于ADCP回声的黑潮-亲潮混合区浮游动物昼夜垂直迁移研究

利用深海潜标所搭载的声学多普勒流速剖面仪(acoustic doppler current profiler,ADCP)得到的后向散射强度Sv,研究了黑潮-亲潮混合区浮游动物的垂向分布、其昼夜垂直迁移(diel vertical migration;DVM)的基本特征、多时间尺度变化及对反气旋式中尺度暖涡的响应.结果表...     

台湾海峡及邻近海域6种对虾食性特征及其营养级研究

本文主要研究台湾海峡及邻近海域6种对虾的食性特征与营养级.研究结果表明,它们皆为混合食性型的甲壳动物.哈氏仿对虾、鹰爪虾和周氏新对虾的主要饵料生物属底栖生物和浮游动物生态类群,中华管鞭虾和须赤虾的主要饵料生物属浮游动物和底栖生物生态类群;它们的营养级范围在1.64～2.14之间.周氏新对虾、角突仿对虾、须赤虾和鹰爪虾属第二营养层次的杂食性动物,哈氏仿对虾和中华管鞭虾属第三营养层次的低级肉食性动物;它们的食物生境宽度范围为6.48～1.24,其大小范围依次为:哈氏仿对虾、中华管鞭虾、鹰爪虾、周氏新对虾、须赤虾、角突仿对虾;6种虾类之间的食物的重叠指数0.008～0.716.除了周氏新对虾与其它虾类之间食物的重叠指数<0.15外,其它5种虾类之间(食物的重叠指数0.387～0.716)都存在竞争饵料资源的问题.挠足类、长尾类、稚幼鱼、多毛类、硅藻类和肉足鞭毛虫是虾类共同争食的饵料生物.     

The colonisation of leaf litter by Chironomidae (Diptera): The influence of chemical quality and exposure duration in a subtropical stream

This study tested the hypothesis that the community composition of Chironomidae will change according to the duration of the exposure of plant leaves in a subtropical stream. In addition, we expected the chemical quality of the detritus to affect the association of Chironomidae with decaying plant materials. The chironomid colonisation of leaf litter from Campomanesia xanthocarpa and Sebastiania brasiliensis was assessed in a subtropical Atlantic forest stream. Litter bags containing leaves from these two species were incubated in the stream for 22 days. We identified 7245 invertebrates associated with the leaf detritus of both plant species (5110 were Chironomidae, 70.7% of the total). Thirteen genera of Chironomidae were identified, with Rheotanytarsus, Thienemanniella and Corynoneura the most abundant (94% of all Chironomidae collected). Chironomidae assemblages changed with the duration of incubation in the stream. The dissimilarity and the functional composition of the Chironomidae communities were related to the chemical composition of the detritus. The chemical components that best explained the composition of the fauna were tannins, the C:N ratio, calcium, and magnesium. However, the functional feeding groups were explained by the chemical variables organic matter and C:N. This study found that the exposure time of the detritus and therefore its level of degradation and chemical composition are important factors determining the characteristics of the Chironomidae assemblage in subtropical streams.     

Diurnal dynamics of streamflow in an upland forested micro‐watershed during short precipitation‐free periods is altered by tree sap flow

Diurnal variations in streamflow are becoming acknowledged as a way of analysing how changing climatic conditions and land use affects watersheds but also as a way to understand watersheds as a whole. Yet not many studies from uplands below 900 mm mean annual precipitation zone are available from European countries. During the 2012 growing season, a sampling campaign took place in an upland forested micro‐watershed, Czech Republic (65 ha). Tree sap flow, rainfall and temperature were measured continuously, while streamflow at the discharge point and soil moisture were estimated from short‐term measurements. Short precipitation‐free periods lasting several days were identified for evaluation of trends in diurnal dynamics of both sap flow and streamflow. The results demonstrated that during these periods, the main factor altering streamflow was almost exclusively tree sap flow. A decrease in streamflow was observed during the day and an increase at night. The decline in sap flow after sunset was accompanied by a continuous increase in streamflow throughout the night up to its initial maximum in the morning. The amplitude in diurnal variations reached 18%. The observed time lag between the diurnal variations of sap flow and streamflow was approximately 2 h. Relatively low changes in diurnal dynamics of streamflow pointed out a strong regulatory role of the forest in buffering water discharge from the catchment. Copyright © 2015 John Wiley & Sons, Ltd.     

太湖梅梁湾红鳍原鲌(Cultrichthys erythropterus)食性与个体大小的关系:对生物调控与管理的启示

红鳍原鲌是太湖常见鱼类之一.对2004年11月到2005年10月的样本(236尾)分析结果表明:在食物组成上,红鳍原鲌主要摄食枝角类和小型鱼类,其食物组成随体长变化明显.全长小于130 mm的红鳍原鲌主要摄食枝角类,小型鱼类的重要性相对较低;全长大于130 mm的红鳍原鲌以小型鱼类为主要食物.在对浮游动物的摄食选择性上...     

DDT对细巧华哲水蚤（Sinocalanus tenellus）摄食、呼吸、存活和生殖的影响研究

DDT(dichloro-diphenyl-trichloroethane) as a type of organochlorine pesticides, is an important component of pesticides pollution whose impact on the marine ecosystem is urgently to be evaluated. To investigate the biological effects of DDT on the marine ecosystem, copepods being the main contributor of secondary productivity in the marine ecosystem, were selected as target animals. The influence of DDT on the feeding, respiration, survival, and reproduction of Sinocalanus tenellus(S. tenellus) was analyzed and the antioxidant enzymes activities in the individuals were measured under different exposure concentrations of DDT. The 48 h median lethal concentration(LC50) and 96 h LC50 of DDT to S. tenellus were 5.44 and 2.50 μg/dm3, respectively. The filtration rates, grazing rates, and respiration of S. tenellus decreased apparently with increased DDT concentrations. Under lower concentration(625 ng/dm3) of DDT, the activities of the antioxidant enzymes, including superoxide dismutase and catalase in the animals increased significantly compared with those in the animals without any exposure to DDT, which suggested that the antioxidant enzymes can protect the animals from oxidative damage. However, the activity of the antioxidant enzyme decreased when the animals were exposed to higher concentration(1 250–2 500 ng/dm3) of DDT. The survival rate of both females and males was reduced when they were exposed to DDT less than 250 ng/dm3, but females showed higher survival rate than males when they are under the same concentration. The hatching ratio and the egg diameters of S. tenellus decreased significantly when they were exposed to DDT with a concentration of 25 and 250 ng/dm3, however, the cumulative egg production did not show any significant variation when the animals were exposed to the above DDT concentration. These data in the preset study suggested that exposure to DDT can cause the variation of the species composition of copepods, and further affect the marine ecosystem.     

饥饿对条纹锯鮨仔鱼的存活、摄食及生长的影响

在温度(22.9±0.8)℃、盐度30～32、DO≥5.0mg/L、pH7.8～8.2, 光照强度40～100lx条件下,对人工孵化的条纹锯鮨仔鱼开展饥饿胁迫对其存活、摄食、生长的变化规律的试验研究及影响,确定仔鱼的不可逆点（PNR）。结果显示,仔鱼在孵化后2d开口摄食,仔鱼体长开始下降,从内源营养期转入混合营养期,持续1d;3d时卵黄囊、油球消失,仔鱼体长增加,进入外源营养期,初次摄食率可达到68.25％。3d12h时初次摄食率最高达到88.24％,之后初次摄食率逐渐下降,5d时初次摄食率下降为37.5％,可知条纹锯鮨PNR=5。6d12h时试验组仔鱼全部死亡。结果表明,内源营养期对照组与试验组无显著差异,对卵黄囊与油球的利用率相似。混合营养期,仔鱼体长出现负增长,且试验组负增长速率明显高于对照组。外源营养期,试验组仔鱼体长持续下降,至PNR时体长负增长速率加快,死亡率增加,直至全部死亡;对照组仔鱼体长开始增长,死亡率逐渐下降并趋于稳定。对照组仔鱼生长模式：快速生长的内源性营养期-微弱负增长的混合营养期-正常生长的外源营养期;试验组生长模式：快速生长的内源性营养期-微弱负增长的混合营养期-可建立外源摄食的负增长期和不可建立外源摄食的负增长期4个阶段。条纹锯鮨仔鱼孵出后2～5d为摄食的关键时期。