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1.
Assemblages of zooplankton and epibenthic invertebrates were collected from a commercial Penaeus monodon (Fabricius) pond at fortnightly intervals over an entire grow‐out season. The pond inlet and outlet water were also sampled intensively over three 1‐week periods throughout the season. Before stocking the ponds with shrimp postlarvae, copepods dominated the zooplankton. Immediately after the ponds were stocked, there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods, suggesting heavy predation by shrimp postlarvae. For the rest of the season, barnacle nauplii were the dominant zooplankton component in the pond. Pond water exchanges had little detectable influence on the composition or density of the zooplankton assemblage. Instead, the dominance of barnacle nauplii appeared to have been maintained by steady recruitment due to barnacle reproduction in the pond. While changes in the biomass of pond zooplankton were not correlated with physico‐chemical characteristics, changes in density were positively correlated with temperature, and negatively correlated with pH, dissolved oxygen and secchi disc readings. Epibenthic faunal density peaked at the end of the season, while the biomass peaked during the middle part of the season. Sergestids (Acetes sibogae Hansen) were the most abundant epibenthic taxa. No correlations were found between physico‐chemical parameters and epibenthic fauna biomass or density. Abundances of epibenthic fauna were not related to zooplankton densities, suggesting that trophic interactions between these assemblages is not important. No Acetes were captured in samples of outlet water, and only on a single occasion were large numbers captured in the inlet water; after this, there was a notable increase in the number of Acetes in the pond. This evidence, together with the lack of an increase in the size of Acetes during the season, suggests that water exchange is an important but unpredictable source of recruitment of epibenthic fauna into the pond. The results emphasize the benefits of ensuring that appropriate zooplankton assemblages have been introduced into the ponds, when they are filled, to support the shrimp immediately after stocking. This will depend on the initial inoculum and may be difficult to manipulate with water exchanges once established. Assemblages of epibenthic fauna appear more likely to change with exchanges and may need to be monitored across the season, particularly if their presence reduces production through adverse impacts such as competition with postlarvae, introduction of disease or deteriorated water quality.  相似文献   

2.
Shrimp pond zooplankton dynamics and the efficiency of sampling effort   总被引：1，自引：0，他引：1  
The abundance and species composition of zooplankton assemblages were examined in a commercial Penaeus monodon (Fabricius) aquaculture pond in subtropical Australia. Numbers and biomass of zooplankton in the surface tows (142 µm mesh) varied from 2080 L?1 (2466 µg L?1) to < 1 L?1 (15 µg L?1). Peak zooplankton abundance and biomass occurred at the beginning of the shrimp farm season. The small copepod Oithona australis Nishida was dominant during these peaks in abundance although other species were common, including small, low‐salinity copepods in the first year and larger marine copepods in the second year. Irrespective of taxa or size, zooplankton abundance declined rapidly after the stocking of P. monodon postlarvae, indicating high levels of non‐selective predation. For the remainder of the grow‐out season, mean zooplankton abundance was below 1 L?1 in the first season and below 3 L?1 in the second season. The factors that maintain the abundance of these zooplankton assemblages at these relatively low levels are poorly understood but may include a deterioration pond water quality. At these lower levels of abundance, the copepods Acartia pacifica Steuer and Acartia sinjiensis Mori were relatively common during the middle phase of the production season, with barnacle nauplii increasing in abundance during the later stages of the grow‐out season. Analysis of fixed effects showed that there were significant differences in total zooplankton abundance between farm production seasons and occasion within season, and time (day or night). Analysis of random effects demonstrated that the dominant source of variation, in total zooplankton abundance, was day‐to‐day changes within sampling occasions. The complexity of temporal and spatial patterns in the abundance, distribution and composition of zooplankton assemblages in shrimp ponds presents significant challenges in designing sampling programmes that accurately quantify temporal or spatial trends. Our results have shown that sampling for more than four consecutive days, at more than one site, is necessary to accurately assess such trends.  相似文献   

3.
The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial shrimp (penaeid prawn) pond in subtropical Australia. Physicochemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 μm mesh) varied from 111.7 ind. L?1 (324 μg L?1) to 8.3 ind. L?1 (44.2 μg L?1). Immediately after the ponds were stocked with shrimp postlarvae there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods. We attributed this to predation by the shrimp postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. Changes in abundance and biomass of the zooplankton assemblage were not correlated with physicochemical characteristics. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m?2 and the biomass at 0.8 g m?2. Unlike zooplankton, the peaks in abundance of epibenthos did not correspond to the peaks in biomass. This was due to the large differences in the size of the dominant taxa across the season. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples, with amphipods abundance increasing towards the end of the growout. Negative correlations were found between epibenthos abundance and pH and temperature. These relationships were strongly influenced by the high abundances of amphipods and may reflect an effect on the growth of macroalgae in the pond rather than a direct effect on the epibenthos. No correlations were found between epibenthic fauna biomass and physicochemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities, indicating that this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes in abundances of zooplankton or epibenthos assemblages. Zooplankton clearly contribute to the nutrition of shrimp postlarvae immediately after stocking. The establishment of an abundant assemblage of zooplankton before stocking shrimp postlarvae would appear to be beneficial, if not essential. Later in the season, zooplankton and epibenthos apparently contribute little to shrimp biomass. Owing to their relatively low biomass, the consumption of shrimp feeds by epibenthos is likely to be insignificant compared with that of the shrimp.  相似文献   

4.
试验探讨了施用生物渔肥(绿源生)后水体中浮游植物和浮游动物的变化。试验取2个水泥养殖池,其中一个为试验池,施入生物渔肥量为4 g/L,另一个为不施肥的对照池。试验结果表明:施用生物渔肥后试验池中的浮游植物在第2天开始迅速增长,第4天达到生长高峰,比对照池同期增长116.25%,硅藻门取代绿藻门成为优势种群;试验池中的原生动物在第4天达到最大值,比对照池增长16.18%,轮虫、枝角类,桡足类在第6天大量增长,比对照池分别增长30.40%、20.59%和17.46%;试验池浮游生物总量在施入渔肥后的第12天仍高于对照池。本试验条件下,生物渔肥对浮游植物和浮游动物的种类影响不大,但对浮游植物和浮游动物的密度影响较大。  相似文献   

5.
对虾工厂化养殖与池塘养殖系统结构与效益比较分析   总被引：4，自引：0，他引：4  
从浮游植物、浮游动物、底栖生物、水质因子4个方面对工厂化对虾养殖和池塘对虾养殖生态系统的差异进行了观察和分析。结果表明,工厂化对虾养殖系统中浮游植物、浮游动物及底栖生物的丰度均低于池塘对虾养殖系统(分别为22815个/ml<31590个/ml,490.5个/L<650.0个/L,4.5个/10cm2<267.5个/10cm2),而溶解氧(DO)含量、氨态氮(NH4-N)和无机磷(PO4-P)浓度均高于池塘养殖。工厂化养殖对虾的生长量、生长速度及存活率均低于池塘养殖,但其养殖密度高,能很好的弥补生长速度之不足,更好的利用水体获得更高的单位生产量。  相似文献   

6.
We compared production variables between channel catfish, Ictalurus punctatus, nursery ponds fed according to industry standards, that is feeding immediately at stocking, to an alternative practice of delaying feeding for 6 wk after stocking in an effort to utilize natural pond productivity and reduce feed use. Twelve 0.04 ha ponds were fertilized and stocked with swim‐up fry (4–5 d posthatch) at a rate of 10,000/pond (250,000/ha). Ponds were then randomly assigned to either the standard feeding protocol (feeding daily starting immediately at stocking) or an alternative feeding protocol (no feeding until 6 wk post‐stocking). After 18 wk of production, there were no differences in water quality or zooplankton abundance between the two treatments. Fish length was not affected by treatment throughout the study, and survival and total weight harvested were similar. Total kg of feed fed was significantly reduced in the delayed feed treatment, averaging 26 kg/pond less feed fed. If proper fertilization practices are implemented, large numbers of desirable zooplankton for catfish fry culture are attained, and these zooplankton are able to sustain catfish fry stocked up to 250,000/ha. Therefore, no commercial diets are required during the first 6 wk of culture, saving over $95.55/ha in initial feed costs.  相似文献   

7.
ABSTRACT

Production of fingerlings from very small fry depends upon an initial high concentration of rotifers followed by high densities of crustacean zooplankton. High fertilization rates lead to increased zooplankton production but often cause poor water quality conditions that aeration may alleviate. This study was designed to determine the effects of constant, nocturnal, and no aeration on water quality, primary productivity, and standing crops of phytoplankton and zooplankton in heavily fertilized nursery-size ponds that contained no fish.

Four 0.04-ha ponds were aerated continually; four ponds were aerated only at night with a 372-W (1/2 hp) paddlewheel aerator; and four ponds were not aerated. For 21 days after they were filled on July 21, 1999, the ponds received 1,224 kg/ha rice bran and 581kg/ha liquid 9-27-0 fertilizer. Water quality variables, primary production, chlorophyll-a and zooplankton were sampled daily.

Constant aeration resulted in several conditions more conducive to survival of fish fry, such as higher zooplankton densities, more moderate temperatures, and safer dissolved oxygen levels than did nocturnal aeration or no aeration. However, the development of a higher standing crop of phytoplankton and higher total ammonia concentrations in the turbulent, constantly aerated ponds resulted in higher un-ionized ammonia levels that were not favorable to survival and growth of fry. The high concentrations of zooplankton that developed in the aerated ponds have good potential for cropping to inoculate other ponds or to provide live foods for tank culture of zooplanktivorous fish.  相似文献   

8.
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.  相似文献   

9.
The response of phytoplankton, zooplankton and benthos to four aeration rates was evaluated in ponds farming white shrimp, Penaeus vannamei Boone, with less than 5% water exchange. Phytoplankton biomass (measured as chlorophyll-fl) was higher in ponds with aeration rates of 0 and 6 h day?1 than in those with rates of 24 hday?1. The abundance of zooplankton and benthos (organisms m?2) were higher in ponds with aeration rates of 0 and 6 h day?1, and lower in ponds with rates of 12 and 24 h day?1. The nauplii of different crustaceans, copepods and larval polychaetes were the most abundant organisms of the zooplankton community. Differences in zooplankton composition were observed among treatments. Polychaetes were the most abundant benthic organisms during the culture period. These organisms were more abundant in ponds with lower aeration rates. The guts of shrimp from ponds with aeration rates of 0 and 6 h day?1 had a higher abundance of zooplankton and benthic organisms than those from the other treatments. That abundance decreased over time in all treatments. Shrimp had better growth in ponds with an aeration of 6 hday?1. Survival and yield were similar in ponds with aeration rates of 6, 12 and 24 h day?1, and lower in ponds with rates of 0 h day?1.  相似文献   

10.
研究了2009年5-9月鲟亲鱼养殖池塘中浮游生物的种类组成,细胞数量、优势种组成和随季节的变化。结果显示：鲟亲鱼的活动导致养殖池塘沉积物再悬浮,水体透明度较低。浮游植物的种类组成以绿藻门（Chlorophyta）的月牙藻（Selenastrum spp．）和小球藻（Chlorella spp．）等小型个体为主,浮游植物密度1．0883×lO^7ind．／L—1．5662×lO^7ind．／L,生物量14．6438～19．2535mg/L。浮游动物以轮虫（Rotifera）和桡足类（Copepoda）为优势种群,浮游动物密度162．0000ind／L～560．0000ind／L,生物量0．3795～1．5482mg／L。研究显示,鲟亲鱼的活动是决定池塘浮游生物的群落结构变化的重要过程之一。  相似文献   

11.
珠江三角洲地区精养淡水鱼塘浮游植物功能群特征   总被引：2，自引：1，他引：1  
分别于养殖前期(5月)、中期(9月)和后期(12月),对珠江三角洲地区主养草鱼(Ctenopharyngodon idellus)、大口黑鲈(Micropterus salmoides)、云斑尖塘鳢(Oxyeleotris marmoratus)和乌鳢(Channa argus)4个品种池塘中的浮游植物功能群进行研究。结果表明,采样池塘浮游植物丰度、物种多样性指数较高,密度均值达1.32×10~8 cell/L,最大值为3.00×10~8 cell/L,生物量均值为168.17 mg/L,最大值为345.41 mg/L;共鉴定到196种(含变种变型)藻类,分属于绿藻(91种)、裸藻(40种)、硅藻(27种)、蓝藻(23种)、甲藻(7种)、隐藻(4种)、黄藻(3种)、金藻(1种)等8大藻门;采样池塘藻类可划分出A、B、C、D、F、G、G_2、H1、J、K、L_1、L_M、L_0、M、MP、N、P、S1、S2、T、T_D、W1、W2、W_S、X1、X2、X_(Ph)、Y等28个功能群;频率分析发现C、F、J、MP、N、P、W1、X2、Y、K、L0、M、W2等主要优势功能群在精养池塘中出现频率高,生物量比重大,说明池塘浮游植物群落稳定,整个养殖过程水体的生态功能比较单一;对环境因子与主要优势功能群进行冗余分析(RDA),得到池塘浮游植物功能群分布状况的首要影响因素是有机质含量(COD_(Mn)),其次为营养物质含量水平(TP和N:P),最后为水体物理环境,包括透明度(SD)、pH、溶解氧(DO)、总可溶性固体(TDS)和水温(WT)。研究发现,池塘水体浮游植物功能群数养殖中期多于前期和末期,并在养殖中期水体交换量大的大口黑鲈和云斑尖塘鳢池塘较为突出,表明在高密度精养池塘中,进行充足的水体交换是高温时期防控水质恶化的重要措施。基于传统的物种多样性指数方法,判定池塘水质状况为洁净,但以浮游植物功能群生境特征判定水体污染严重,且与水体理化环境测定结果和现场水体表观相符,说明功能群比多样性指数能更好地反应池塘水质的真实状况。  相似文献   

12.
于高温多雨季节对广东省清远市鳜养殖基地的6个鳜（Siniperca chuatsi）及饵料鱼养殖池塘发病前后的浮游生物组成进行了调查分析。结果表明,易发病池塘,水中浮游生物总生物量比其他池塘略低。浮游植物优势种均为微囊藻（Microcystis sp.）,颤藻（Oscillatoria sp）等蓝藻。此外,池塘出现出血病症状时,浮游生物的马格利夫（Margalef）丰度指数和香农（Shannon-weaver）多样性指数均处于较低水平,这两项指数可作为池塘发病的预警参考指标。在实际生产中,平时应注意调节水质,以稳定水中浮游生物的数量和组成,在天气不佳时更应多加巡塘,以便及早发现病情。  相似文献   

13.
Abstract— Laboratory studies with pond water samples revealed that 5 mg/L active chlorine was needed to provide enough chlorine residual to reduce biological activity. Treatment of channel catfish ponds with repeated, 0.1-mg/L doses of active chlorine from calcium hypochlorite at 6- to 8-d intervals, as sometimes done by catfish farmers, had little influence on water quality. Dissolved oxygen, total ammonia-nitrogen, and chlorophyll a concentrations and pH were similar between treated and control ponds. Concentrations of chemical oxygen demand and particulate organic matter were seldom different between treated and control ponds. Channel catfish survival and net production were not improved by chlorine treatment. Thus, chlorination of production ponds during the grow-out period is not a useful technique. Treatment of sediment samples from ponds with up to 1,200-mg active chlorinelkg soil did not reduce bacterial abundance, so chlorination of bottoms of empty ponds may not he an effective disinfection procedure. Chlorination of pond waters with 30-mg/L active chlorine caused complete kill of bacteria 24 h after treatment, although heterotrophic bacteria quickly re-populated the water. Thus, chlorination can be an effective way to disinfect ponds before stocking.  相似文献   

14.
凡纳滨对虾不同养殖密度高位池水体细菌群落动态   总被引：3，自引：2，他引：1  
通过对养殖水体环境基因组DNA中细菌16S rRNA基因V4–V5区的高通量测序和生物信息学分析,研究了两种养殖密度的凡纳滨对虾(Litopenaeus vannamei)高位池水体中细菌群落在养殖过程中的动态。结果显示,养殖过程中各菌群相对丰度变化明显,细菌多样性随时间逐渐提高,优势菌群为变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)、拟杆菌门(Bacteroidetes)、放线菌门(Actinobacteria)和浮霉菌门(Planctomycetes)。随着养殖时间增长,蓝藻丰度所占比例逐渐减少,而变形菌、拟杆菌和浮霉菌丰度逐渐增大,同时养殖前期高密度池浮霉菌丰度显著高于低密度池(P0.01),而其他菌群无显著差异。结果表明,养殖期前50 d不同养殖密度水体细菌群落差异较大,而后30 d内细菌群落的时间异质性大于空间异质性,这意味着高位池水体菌相被划分为两类,到养殖后期菌相快速转变,养殖密度所带来的影响被减弱。  相似文献   

15.
看水越冬及其生物学分析   总被引：1，自引：0，他引：1  
根据黑龙江、吉林地区数十个鱼类越冬池的实测数据 ,从水色、透明度、浮游生物与水体溶氧间的相互关系 ,总结如下规律 :1 水体透明度与浮游植物量负相关 ,与浮游动物量正相关。透明度 <5 0cm者 ,浮游植物丰富而极少浮游动物 ,一般氧气充足 ;透明度 >80cm者 ,多滤食性浮游动物 ,浮游植物少 ,一般溶氧量较低。越冬池透明度以 5 0～ 70cm为宜。 2 根据水体透明度可了解越冬池营养盐的丰欠 ,在越冬中、后期“肥水 (浮游植物多 )易缺肥而瘦水 (浮游动物多 )不易缺肥”。 3 目测冰下水体中鱼类的活动状况和兼测水温变化 ,可为池鱼越冬效果预测提供重要依据  相似文献   

16.
鱼蚌混养对池塘水质、藻相结构及三角帆蚌生长的影响   总被引：2，自引：1，他引：1  
2012年4月26日—2012年12月12日通过在鲢鳙鱼养殖池塘中放养不同密度的三角帆蚌,研究不同三角帆蚌放养比例对鲢鳙鱼养殖池塘中水质、藻相结构及三角帆蚌生长的影响。实验中,鲢鳙放养比例统一为3∶7,总密度为1.5尾/m3。三角帆蚌放养密度则设置4个水平,分别为单养鲢鳙鱼池塘(0只/m3),低密度三角帆蚌混养池塘(0.8只/m3),中密度三角帆蚌混养池塘(1.0只/m3)和高密度三角帆蚌混养池塘(1.2只/m3)。结果显示,混养三角帆蚌池塘的水化指标(TP、PO4-P、NH3-N、NO2-N和NO3-N)均显著低于单养鱼池塘。中密度三角帆蚌混养池塘除NH3-N和化学需氧量(COD)与低密度三角帆蚌混养池塘无显著差异外,其他各项水化指标均显著低于其他3个池塘,并且极显著低于单养鲢鳙鱼池塘。单养鲢鳙鱼池塘藻类平均密度均极显著高于鱼蚌混养池塘,其中在鱼蚌混养池塘中浮游植物密度与三角帆蚌密度成负相关关系。单养鲢鳙鱼池塘的浮游植物生物量均极显著低于中、高密度鱼蚌混养池塘,并且显著低于低密度混养池塘。浮游植物生物量与三角帆蚌密度成正相关关系,鱼蚌池塘中绿藻和裸藻的生物量在养殖过程中上升显著。低、中密度三角帆蚌混养池塘三角帆蚌存活率均显著高于高密度三角帆蚌混养池塘;低密度混养池塘中蚌湿重、壳长及壳宽相对增长率均为最大,显著高于中、高密度三角帆蚌混养池塘。研究表明,养鱼池塘混养三角帆蚌不仅能改善养殖池塘的水质,还能控制藻类数量,促使绿藻和裸藻等大型藻类的生长,提高养殖水体浮游植物的生物量总量,最终还能有效提高三角帆蚌的存活率及生长率。从改善水质,藻相结构,蚌成活率及生长等指标角度考虑,在鲢鳙鱼养殖池塘中,三角帆蚌最佳放养密度为1.0只/m3。  相似文献   

17.
Agricultural limestone and burnt lime are applied either to the water during shrimp production or to pond bottoms between shrimp crops. However, unless the total alkalinity and total hardness of pond water is below 50 mg/L as equivalent CaC03 or the pond soils are acidic (pH < 7), liming is of little or no value. The use of burnt lime should be avoided because this material can cause high pH in water and soil. Chemical fertilizers or manures are used to fertilize brackishwater ponds. Fertilization programs for brackishwater ponds usually require more nitrogen (N) than those for freshwater ponds. Phosphorus (P) fertilization is important both in brackishwater and freshwater ponds. Because water is exchanged often in brackishwater ponds, fertilizer should be applied in small doses and at frequent intervals. Most managers of brackishwater ponds prefer a large proportion of diatoms in the phytoplankton community. An N:P application ratio of 20:l in ponds favors diatoms; in fiberglass tanks with water of low silica concentration, fertilization with silica encouraged an abundance of diatoms.  相似文献   

18.
A participatory on-farm study was conducted to explore the effects of food input patterns on water quality and sediment nutrient accumulation in ponds, and to identify different types of integrated pond systems. Ten integrated agriculture-aquaculture (IAA) farms, in which ponds associate with fruit orchards, livestock and rice fields were monitored in the Mekong delta of Vietnam. Pond mass balances for nitrogen (N), organic carbon (OC) and phosphorus (P) were determined, and pond water quality and sediment nutrient accumulation were monitored. Data were analyzed using multivariate canonical correlation analysis, cluster analysis and discriminant analysis. The main variability in pond water quality and sediment nutrients was related with food inputs and water exchange rates. Water exchange rate, agro-ecological factors, pond physical properties and human waste input were major variables used to classify ponds. Classification was into: (1) low water exchange rate ponds in the fruit-dominated area, (2) low water exchange rate ponds in the rice-dominated area receiving homemade feed, and (3) high water exchange rate ponds in the rice-dominated areas receiving wastes. Pond water exchange rate was human-controlled and a function of food input patterns, which were determined by livelihood strategies of IAA-households. In the rice-dominated area with deep ponds, higher livestock and human wastes were found together with high water exchange rates. In these ponds, large organic matter loads reduced dissolved oxygen and increased total phosphorus concentrations in the water and increased nutrient (N, OC and P) accumulation in the sediments. In the rice-dominated area with wide ponds, higher homemade feed amounts were added to the ponds with low water exchange rate. This resulted in high phytoplankton biomass and high primary productivity. The contrary occurred in the fruit-dominated area, where fish were grown in shallow and narrow ponds, receiving more plant residue which resulted in lower phytoplankton biomass and lower sediment nutrient accumulation.  相似文献   

19.
Plankton community structure and chlorophyll a concentration were compared in twelve 0.1 ha earthen ponds co‐stocked with channel catfish (Ictalurus punctatus Rafinesque, 1818) in a multiple‐batch culture (initial biomass=5458 kg ha?1) and a planktivore, threadfin shad (Dorosoma petenense Güther, 1867; initial biomass=449 kg ha?1), during the April–November growing season. We used a completely randomized design in a 2 × 2 factorial arrangement to test the planktivore level (presence or absence of threadfin shad) and channel catfish feeding frequency (daily or every third day). Channel catfish were fed a 32% protein feed to apparent satiation on days fed. The presence of threadfin shad affected phytoplankton and zooplankton community structure more than did feeding frequency, and the impact in ponds was more pronounced after 1 July. The numbers of all major groups of zooplankton were lower in ponds with threadfin shad, but were unaffected by the feeding frequency. Chlorophyll a concentration before 1 July was higher in ponds with threadfin shad and unaffected by the feeding frequency, whereas after 1 July it was higher in ponds without threadfin shad and that were fed daily. Phytoplankton community structure after 1 July was dominated by nuisance algal bloom genera of cyanobacteria in ponds without threadfin shad and by Bacillariophyceae in ponds with threadfin shad.  相似文献   

20.
The use of open-ended isolation columns (20 m3) as replicable experimental units was evaluated in two Alabama Piedmont ponds. Isolated columns of water differed limnologically from conditions present in the open ponds. Most of these differences were attributed to open pond sites having significantly higher phytoplankton biomass (chlorophyll-a). However, comparison of pond and column variances indicated that samples collected in columns were generally no more indicated that samples collected in columns were generally no more variable than similar samples collected from the pond that surrounded them. Isolation columns could be used as an alternative to replicate ponds for certain types of short-term, pond culture studies.  相似文献   

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