河蟹饵料池中轮虫接种对单胞藻种群增长的影响

研究了河蟹饵料培养池中轮虫接种后浮游植物的种群变动.结果表明:轮虫接种后浮游植物高峰期很快消落,绿藻、硅藻等小型藻类生物量很快下降,而裸藻、甲藻等大型藻类的生物量增加,浮游植物的种类组成趋于大型化.     

施肥后河蟹育苗试验围隔中浮游生物状况及其变动

采用陆基试验围隔的方法研究了施肥后河蟹育苗池中浮游生物的变化情况。施肥后,各试验围隔前期浮游植物生物量随着时间变化明显,迅速达到高峰期。而后,由于轮虫的大量繁殖,使浮游植物生物量又迅速回落;在种群组成上,前期小球藻一直占优势,后期大型藻类大量出现后,小球藻生物量不大;围隔水体中浮游动物主要以轮虫为主,其生物量随着时间的变化明显,但空间分布不明显。轮虫的摄食对浮游植物生物量有影响,二者相互消长,但由于后期大型浮游植物的影响,并没有呈现出典型的负相关关系;桡足类对早期蟹苗危害较大,但后期可成为蟹苗的摄食对象。     

低温条件下轮虫的敞池增殖↑（*）

选择我国东北高寒地区的14个池塘，在低温（＜10℃）条件下采取“冻底”、“晒底”和“搅底”的措施，促使轮虫休眠卵萌发，增殖萼花臂尾轮虫等广温幅的轮虫，使其种群数量的高峰期与当地早繁鱼苗生产同步。试验池轮虫生物量变幅为25．72～73．20mg/L，平均45±13．53mg/L，持     

安乡珊珀湖人工投入后水环境生态效应变化研究

本文就2005年6月至2006年12月对珊珀湖采样进行水质分析和浮游生物的调查,珊珀湖通过人工投入后,N、P的含量明显提高,经过多年的施肥培水珊珀湖的浮游生物数量比1986年增加了10多倍,其平均生物量可达3 819.0万个/L(浮游植物)、10 407个/L(浮游动物)、而且其种群结构也发生了相应的改变,浮游植物中蓝藻门所占的比例上升,从36.9%上升到74.5%,浮游动物则以轮虫为主,轮虫所占的比例从20.0%上升到79.2%,其它营养盐类和微量元素也都明显增加,使珊珀湖成为了一个典型的富营养型湖泊。     

丰水季北京汉石桥湿地浮游生物群落特征多样性分析

为了解近几年对北京市顺义区汉石桥湿地水质调控和管理工作的效果,于2011年6月对湿地浮游植物、浮游动物的种类及种群密度进行了调查和分析,并采用指示生物法和生物多样性指数法对湿地的水质进行了生态评价。结果表明:汉石桥湿地的浮游植物以绿藻门数量最多,占浮游植物总数的57.4 %；硅藻门和蓝藻门次之,分别占19.1 %和12.82 %。其中绿藻门的小球藻(Chlorella sp.),硅藻门的尺骨针杆藻(Synedra ulna)、尖针杆藻(Synedra scus)、舟形藻(Navicula sp.)和小环藻(Cyclotella sp.),蓝藻门的铜绿微囊藻(Microcystis aeruginosa)和水华微囊藻(Microcystis flos-aquae)在5个位点中为优势种。浮游动物以轮虫为主,其中18种轮虫为优势种。从调查情况来看,汉石桥湿地水质总体属中度偏轻污染,说明对湿地的水质调控和管理初步取得成效。     

提高鱼苗培育池轮虫生物量的途径

轮虫是鱼苗的天然饵料，尤其是在鱼苗卵黄囊消失并开始觅食时，因枝角类等体形较大的浮游动物还不能为其吞食，轮虫更是最适口的天然食饵。因此，在发塘时，轮虫数量的多寡直接影响着鱼苗生长的快慢和成活率的高低。鱼池底泥中广泛分布着轮虫的休眠卵，只要生境适合，休眠...     

滆湖北部底泥疏浚的生态效应研究

为研究滆湖北部湖区生态系统对底泥生态疏浚的动态响应,2012年10月~2013年9月在滆湖北部湖区采集沉积物和生物样品,分析底泥疏浚对底泥营养盐含量、浮游植物、底栖动物和大型水生植物群落结构的影响。结果表明,滆湖北部疏浚区的总氮、总磷和有机质营养盐含量低于未疏浚区,说明底泥疏浚是削减沉积物内源负荷的有效手段。与未疏浚区相比,疏浚区浮游植物的密度、生物量有所减少,且群落中蓝藻所占的比例下降,浮游植物多样性指数上升,一定程度上减少了滆湖北部发生蓝藻水华的风险。疏浚区底栖动物中的寡毛类的数量和生物量与未疏浚区基本相等,而摇蚊类和软体动物的密度和生物量则下降了80%以上。底泥疏浚区大型水生植物的种类、覆盖度和生物量与未疏浚区相当。     

池塘轮虫增殖技术

池塘轮虫增殖技术在池塘中直接增殖轮虫，是解决鱼苗开口饵料、降低生产成本、提高鱼苗成活率和质量的有效途径。现将其技术要点作一介绍。１．排水清塘。轮虫是依靠底泥中的休眠卵萌发的。据测定，在养鱼肥水池塘底泥中，平均１ｍ２有轮虫休眠卵几百万至一千多万个，它们...     

万安大坝截流前赣江的浮游植物

本文初步鉴定赣江浮游植物的种类组成和数量变化,同时剖析赣江浮游植物的种群结构来分析赣江的污染状况.     

池塘增殖轮虫技术要点

在池塘中直接增殖轮虫,是解决鱼苗开口饵料、降低生产成本、提高鱼苗成活率和质量的有效途径。现将其技术操作要点介绍如下:1.排水清塘轮虫是依靠底泥中的休眠卵重新萌发的。据测定,在养鱼的肥水塘的底泥中,平均每平方米有轮虫休眠卵几百万至1000多万个,它们是翌年轮虫萌发的“种子”。排水能增加底泥中休眠卵的受热量,清塘可清除轮虫的敌害,更换新水本身对休眠卵是一个良性刺激。所以,在平均水温20～25℃时,每667 m2用生石灰100 kg左右排水清塘,经8～10     

Strategies for Development of Rotifers as Larval Fish Food in Ponds

Strategies to sustain rotifer peak biomass, distribution of rotifer resting eggs in the sediment, and relationship between rotifers and larval fish growth were studied in a series of pond experiments. After the ponds were filled with water, herbivorous rotifers (e.g., Brachionus calyciflorus ) developed first, but were gradually replaced by predatory rotifers (e.g., Asplanchna ). Subsequently, herbivorous cladocerans (e.g., Moina sp) eventually replaced rotifers and dominated the zooplankton community. The occurrence of Asplanchna and Moina indicated the decline of B. calyciflorus . Peak rotifer biomass developed 8–10 d after the ponds were filled with water at 20–25 C, 10–15 d at 17–20 C, 15–20 d at 15–17 C, 20–30 d at 10–15 C, and >30 d at < 10 C. The abundance of resting eggs in the top 5-cm sediment varied from 6 to 83/cm². About 25% of resting eggs were buried in the top 5-cm sediment but the number of resting eggs decreased with increased sediment depth. Optimum rotifer biomass for silver carp Hypophthalmichthys molitrix larvae stocked at 1,500,000/ha was 20–40 m/gL. High rotifer biomass (>20 mg/L) usually lasted 3–5 d, but could be prolonged by pond fertilization or cladoceran controls. A weekly application of dipterex at 0.05 mg/L reduced cladoceran biomass but enhanced rotifer biomass. Our results indicate with a careful management plan it is possible to synchronize the rotifer development with larval fish stocking.     

Effect of Environmental Factors on Development of Rotifer and Copepod Nauplii Populations in Sunshine Bass Morone chrysops×M. saxatilis Nursery Ponds without Fish

Knowledge of the effect of environmental factors on timing and production of zooplankton populations would enable sunshine bass Morone chrysops × M. saxatilis farmers to stock fry when live food is most available and thereby increase fry survival. Relationships of morning water temperature, morning and average daily air temperature, day length, number of rain days and daily rain fall, and dissolved oxygen concentrations to time required for rotifer and copepod nauplii populations to peak in freshly filled freshwater nursery ponds was determined. Relationships of the same independent variables to concentrations of rotifers and copepod nauplii at the peak were also determined. For rotifers, day length, dissolved oxygen, and water and air temperatures were highly correlated with time to the peak density, but not concentration of rotifers. Time required for copepod nauplii densities to peak was associated with rain events; whereas, nauplii concentration was related to day length, dissolved oxygen levels and, to a lesser extent, water and air temperatures. Regression equations of the independent variables had very low predictive value for rotifer or nauplii densities or time to reach initial peak nauplii populations. Regressions of day length, morning water temperature, morning and average daily air temperature had moderate values ( r ² > 0.7) for predicting time to initial peak rotifer densities.     

Fish larvae: zooplankton relationships in microcosm simulations of earthen nursery ponds. II. brackish water system

A simulation of the effects of predation intensity on zooplankton composition in brackish water nursery ponds was carried out in order to address the problem that commercial fish nurseries encounter in obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed. The experimental system consisted of twelve 130 l containers with treatments of four densities (0, 1, 2, or 4 larvae l⁻¹) of common carp (Cyprinus carpio L.), stocked on the 6th day after filling the containers. Zooplankton-environment relationships were explored using factor analysis. Factor analysis allowed identifying several groups of zooplankters that responded in different ways to fish larvae predation pressure. The first factor represented a general measurement of rotifer abundance, and the second identified the direct effect of size-selective fish predation. Since no rotifers were present in the filling water, all these species were autochthonous populations that hatched from resting forms in the sediment and reproduced. In the absence of fish predation, this led to a steep rotifer increase. Fish predation started when the rotifer concentration was just starting to increase and their direct predation reduced and delayed the rotifer abundance peak. This effect increased with the increase in fish larvae density. Estimations of rotifer consumption by fish larvae in this experiment were higher than similar calculations from data of the literature, which led us to test the hypothesis that factors other than direct predation were affecting rotifer population dynamics. The mechanisms involved in rotifer population regulation are discussed. It was concluded that in commercial nurseries, increased larvae production can be achieved by keeping the larvae density at an intermediate level and stocking fish to match the increasing phase of the rotifer peak. Under reasonable larvae density (up to 2 l⁻¹) it seems that the direct predation effect of fish larvae on rotifer dynamics is minor, compared to fish induced self regulation.     

Effects of trichlorfon, fenthion, and diflubenzuron on the zooplankton community and on production of reciprocal-cross hybrid striped bass fry in culture ponds

The application of trichlorfon, diflubenzuron, or fenthion to fertilized culture ponds stocked with 5-day-old, reciprocal-cross, hybrid striped bass fry resulted in an initial reduction in the concentration of rotifers and longer-term alteration of zooplankton successional stages, including changes in concentrations of rotifers, cladocerans, and copepods. Culture ponds without applied chemicals had the highest concentrations of small rotifers when fry were stocked, followed by high concentrations of cladocerans, copepod nauplii, and adult copepods. Fry survival in untreated ponds was higher than in chemically-treated ponds. Initial high concentrations of copepods in some ponds corresponded with low fry survival. Untreated ponds that were filled at the time of broodfish spawning, and stocked with fry 5 days later, had the highest fry survival rates, corresponding with peak rotifer concentrations, followed by a typical zooplankton succession.     

Fish larvae – zooplankton relationships in microcosm simulations of earthen nursery ponds. I. Freshwater system

To address the commercial nurseries problem of obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed, a simulation of the effects of predation intensity on zooplankton composition in freshwater nursery ponds was carried out in an experimental system of twelve 130-liter containers. Treatments consisted of two densities (1 or 2 larvae l⁻¹) of common carp stocked on the 4th day after filling the containers and a control without fish. Zooplankton–environment relationships were explored using factor analysis. Several groups of zooplankters that respond in different ways to fish larvae predation pressure were identified. The first factor was a general measurement of zooplankton abundance that mainly reflects allochthonous rotifer species that entered the system with the filling water, replaced in time by autochthonous species that hatched from resting eggs in the sediment. The second factor identified the direct effects of size selective fish predation, and the third showed indirect effects of high fish density. Larvae growth rate matched the plankton availability: high just after stocking, when they fed on the abundant but declining numbers of allochthonous rotifers; then decreased drastically and increased again when hatching of resting eggs of autochthonous rotifers and the availability of the crustacean preys preferred by the fish, increased. It was concluded that in commercial nurseries increased larvae production can be achieved just by stocking fish earlier than the 4th day after pond filling, to match the rotifer peak.     

The culture, zooplankton dynamics and predator-prey interactions of Chesapeake Bay striped bass, Morone saxatilis (Walbaum), in estuarine ponds

Abstract. Four 0.05-ha research ponds were filled with brackish water (12 ppt) for the purpose of evaluating zooplankion dynamics and predator-prey interactions. Three of the ponds were stocked with Chesapeake striped bass, Morone saxatilis (Walbaum). All ponds were fertilized to stimulate zooplankton blooms using a protocol that has been successful in freshwater systems. Zooplankton was dominated by four major groups: rotifers, copepod nauplii, Eurytemora adults and Eurytemora copepedites with rotifers and the nauplii being the most abundant organisms found. Rotifer populations peaked 15-20 days after filling while the copepods peaked 17-22 days after filling. Fish production was very similar to that found in freshwater ponds with an average yield of 84.4 kg/ha (2.0 kg/ha/day) for phase 1 fish (=45mm). Food selectivity indices indicated striped bass avoided both rotifers and copepod nauplii and preferred adult and copepedite Eurytemora as a food item. However, due to various problems associated with sampling, these selectivity results should be considered with caution. The findings of this study reveal fertilization regimes used successfully in freshwater production systems can be applied in an estuarine environment.     

褶皱臂尾轮虫培养若干问题探讨

本文就轮虫生产性培养过程中接种密度、投饵量、水质、轮虫生长和营养强化等方面的问题进行探讨,认为:接种密度在用单胞藻培养时应为10～30个/ml,用酵母培养时20～50个/ml;酵母投喂量0 3～0 35g/百万,投喂量不宜过大;酵母投喂的轮虫使用前2d最好用单细胞藻类强化。     

Production and Collection of Copepod Nauplii from Brackish Water Ponds

Copepod nauplii are a nutritious food item for first-feeding marine fish larvae. Unfortunately, mass culture techniques for producing copepod nauplii are not well established. Copepod nauplii can be collected from wild zooplankton populations or specially prepared ponds and transferred to larval fish tanks for feeding. This study evaluated the use of two trapping methods for harvesting zooplankton, particularly copepod nauplii, from fertilized ponds and the impact on the zooplankton population. Nine, 0.11 ha brackish-water (～2-7 ppt salinity) ponds were filled and fertilized with organic and inorganic fertilizers. The change in zooplankton abundance, mainly rotifers, nauplii and adult copepods, was monitored in the ponds for 22 d following initial pond filling. Beginning on day 8, three ponds were trapped with a large plankton net (Trap I), three with a pump and bag trap method (Trap II), and three ponds were not trapped. The ponds were trapped with the corresponding method for 1 h per day, for 15 d. The two trapping methods were similar in their efficiency to harvest nauplii, averaging 8,383,400 ± 2,508,378/h and 6,695,822 ± 433,533/h for Traps I and II, respectively. The zooplankton harvested by Trap I was not correlated to the densities in the ponds. However, the number of rotifers and nauplii harvested by Trap II was correlated to the rotifer and nauplii densities in the ponds. Both trapping methods were similar in terms of labor requirements and ease of use. Both methods were effective in collecting zooplankton without negatively impacting pond abundance.     

Effects of Timing of Common Carp Larvae Stocking on Zooplankton Succession in Earthen Nursery Ponds: A Microcosm Simulation

Large‐scale commercial nurseries face problems in obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed. To address these problems a simulation of the effects of timing of fish larvae stocking after pond filling on zooplankton composition was carried out. The experimental system consisted of twelve 130‐L containers, in which zooplankton populations were exclusively autochthonous (hatched from resting eggs in the sediments, not entering with the filling water). Treatments consisted of stocking 2‐d‐old common carp larvae on the fourth and sixth days after water filling and a control without fish. The effects of timing of stocking on fish larvae growth and on zooplankton composition were explored using factor analysis. This enabled the identification of several groups of zooplankters that respond in different ways to predation by fish larvae. FACTOR1 was a general measurement of small rotifer abundance. It showed earlier increase in response to the exposure to fish predation, and toward the end of the experiment indicated that fish also preyed on them. FACTOR2 identified the direct effects of size‐selective fish predation on zooplankton that differed according to timing of fish larvae stocking. FACTOR3 identified benthic rotifers, whose density in the plankton increased as a result of fish disturbance of the bottom sediment and decreased as a result of fish predation, also according to timing of fish larvae stocking. In the studied system no rotifers were present in the filling water and the zooplankton peak of autochthonous populations took a while to develop. Under this zooplankton succession pattern, stocking fish larvae before the rotifer concentration started to increase (Day 4) greatly affected their own food resources. The strong predation pressure exerted on the emergent resource retarded the zooplankton increase for 4 d. It also changed the composition toward smaller species and forced fish to feed on less preferred resources, which resulted in reduced fish growth rate. Stocking fish larvae after the rotifer concentration had started to increase (Day 6) allowed the fish to come across increasing amounts of zooplankton of large‐size species, not requiring the exploitation of small benthic rotifers. This resulted in better fish growth rates. Thus, increased larvae production in commercial nurseries can be achieved by matching fish stocking with the increasing phase of the zooplankton peak.