Food web structure and ecosystem properties of the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project

Hongze Lake (HZL) is the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project. However, there is surprisingly little ecological understanding on this important ecosystem, especially under the potential water diversion threats. Here, a mass-balance model was constructed to characterize trophic structure and ecosystem properties of HZL. The model outputs indicated that small sized fishes have dominated the food web, and fishery resources were suffered from high pressures of overfishing. Mandarin fish, Northern snakehead, Other piscivores and Large culters occupied the top trophic niche, while macrophytes, phytoplankton and detritus consisted of the main energy sources. HZL food web was fairly based on two main food chains: primary production (49.9%) and detritus pool (50.1%), but transfer efficiencies in both chains were relatively low as 6.37% and 6.49%, respectively. Predator-prey interactions, trophic cascading effects and competition of different components were also exhibited in the mixed trophic impacts map. Results from the network analysis suggested that the HZL ecosystem was a relatively mature ecosystem since the total primary production to respiration (TPP/TR) and to biomass (TPP/TB) were 1.138 and 6.922, and the Finn Cycling Index was 6.77%. Nevertheless, the relatively low values of Connectance Index (0.195) and System Omnivory Index (0.089), together with Finn's Mean path Length (2.849) also indicated that the food web structure was vulnerable, characterized by linear, rather than web-like features. Our results suggested that the HZL ecosystem would be potentially affected by the future inter-basin water diversion, and thus ecosystem-based strategies were also presented accordingly.     

黄河口邻近水域贝类生态容量

黄河口邻近水域是著名的贝类生产区,四角蛤蜊、菲律宾蛤仔、文蛤等是该海域重要的增养殖品种.目前,贝类底播养殖最高年产量达30万t,实现产值15.4亿元.然而,贝类过度增殖,将引起海域环境的变化,继而导致贝类死亡率的增加,影响生态系统的健康.因此,基于生态系统的贝类生态容量评估至关重要.本研究利用Ecopath with Ecosim软件构建了黄河口邻近水域生态系统营养通道模型,在此基础上分析了该生态系统功能群间的相互影响、生态系统的总体状态,并评估了贝类的生态容量.结果表明: 系统的总初级生产量/总呼吸(TPP/TR)为3.45、总初级生产量/总生物量(TPP/B)为38.91,同时具有较低的循环指数(FCI=0.028)、较高的剩余生产量961.24 t·km^-2·a^-1和较低的系统连接指数(CI=0.38),说明该系统目前处于发育的不稳定期.贝类生物量的增加对虾虎鱼、虾类和蟹类有正影响, 对中上层鱼类、底层鱼类、海蜇、浮游动物等功能群有负影响.当前贝类的生物量是5.5 t·km^-2,有一定的增殖潜力.模型估算得出的贝类生态容量是18.22 t·km^-2,该研究结果可为黄河口邻近水域渔业资源的可持续发展提供管理依据.     

基于Ecopath模型的莱州湾中国对虾增殖生态容量

通过增殖放流,增加优质渔业资源、改善种群结构是渔业资源养护的重要手段,而增殖生态容量的研究是科学实施增殖放流的前提.本文根据2009-2010年的渔业资源与生态环境数据,构建了由26个功能群组成的莱州湾生态系统Ecopath模型,利用该模型分析了生态系统的总体特征、营养相互关系与关键种,计算了放流品种中国对虾的增殖生态容量.结果表明：系统的总初级生产量/总呼吸(TPP/TR)为1.53,总初级生产量/总生物量(TPP/B)为24.54,同时具有较低的循环指数(FCI=0.07)、较高的剩余生产量（434.41 t·km^-2·a^-1）和较低的系统连接指数(CI=0.29),该系统目前处于发育的早期阶段.中国对虾目前不是莱州湾生态系统的关键种,当前中国对虾的生物量为0.1143 t·km^-2,有较大的增殖潜力;当生物量增长25.8倍时,仍不会超过增殖生态容量2.9489 t·km^-2.     

Evaluating Stocking Efficacy in an Ecosystem Undergoing Oligotrophication

Oligotrophication has negatively affected fisheries production in many freshwater ecosystems and could conceivably reduce the efficacy of stockings used to enhance fisheries. In Lake Michigan, offshore oligotrophication has occurred since the 1970s, owing to reductions in total phosphorus (TP) inputs and nearshore sequestration of TP by nonindigenous dreissenid mussels. We evaluated simultaneous effects of stock enhancement and oligotrophication on salmonine species (Chinook salmon Oncorhynchus tshawytscha, lake trout Salvelinus namaycush, and steelhead O. mykiss) that support valuable recreational fisheries. We employed a novel application of an Ecopath with Ecosim model by conducting a full factorial simulation experiment. Our design included multiple levels of salmonine stocking, consumption by invasive quagga mussels (Dreissena bugensis), and TP that were informed by manager interests. Under all levels of TP and quagga mussel consumption, our results showed that stock enhancement could still increase salmonine biomass, but positive responses were stronger for lake trout and steelhead than Chinook salmon. Simulations showed that quagga mussel consumption has deleterious effects on pelagic-oriented prey fishes and Chinook salmon, which feed almost exclusively on the pelagic-oriented alewife (Alosa pseudoharengus). In summary, results from our simulation experiment suggested that lake trout and steelhead are better suited to the current ecosystem than Chinook salmon, and therefore, stock enhancement provides the highest gains for these two species. Furthermore, simulated biomass of all recreational salmonine species increased with increasing TP, indicating the need for managers to consider how potential future oligotrophication will limit the carrying capacity of salmonine biomass in Lake Michigan.     

基于Ecopath模型的千岛湖生态系统结构和功能分析

为探索千岛湖生态系统现状及其历史变化, 根据2016年千岛湖的渔业资源与生态环境调查数据, 构建了千岛湖生态系统的 Ecopath 模型, 综合分析系统的能量流动过程、营养级结构和生态系统总体特征。2016年千岛湖 Ecopath 模型由18个功能组组成, 有效营养级范围为1—3.41, 牧食食物链的能量流动占系统总能量的56%。系统杂食指数(SOI)、联结指数(CI)、Finn循环指数分别为0.13, 0.26和5.15%。千岛湖与其他湖泊和水库比较, 其生态系统的各功能组的聚合度较高, 联结程度较为紧密, 物质再循环比例较高, 系统较为成熟。但千岛湖的系统总流量较低为24698.27 t/(km2·a), 总初级生产量与总呼吸量的比值为6.51, 表明系统总体规模较小且仍处于发展阶段。根据千岛湖生态系统历年变化趋势分析: 千岛湖生态系统的总体规模有变大趋势, 稳定性和复杂性有所增强, 但营养交互关系变弱, 系统抵抗外界干扰的能力仍较低。同时, 千岛湖生态系统的初级生产者转化效率较低, 食物网趋于简单, 应采取适当的管理措施, 以保障千岛湖生态系统的健康发展。     

Sustainability of the Lake Superior Fish Community: Interactions in a Food Web Context

The restoration and rehabilitation of the native fish communities is a long-term goal for the Laurentian Great Lakes. In Lake Superior, the ongoing restoration of the native lake trout populations is now regarded as one of the major success stories in fisheries management. However, populations of the deepwater morphotype (siscowet lake trout) have increased much more substantially than those of the nearshore morphotype (lean lake trout), and the ecosystem now contains an assemblage of exotic species such as sea lamprey, rainbow smelt, and Pacific salmon (chinook, coho, and steelhead). Those species play an important role in defining the constraints and opportunities for ecosystem management. We combined an equilibrium mass balance model (Ecopath) with a dynamic food web model (Ecosim) to evaluate the ecological consequences of future alternative management strategies and the interaction of two different sets of life history characteristics for fishes at the top of the food web. Relatively rapid turnover rates occur among the exotic forage fish, rainbow smelt, and its primary predators, exotic Pacific salmonids. Slower turnover rates occur among the native lake trout and burbot and their primary prey—lake herring, smelt, deepwater cisco, and sculpins. The abundance of forage fish is a key constraint for all salmonids in Lake Superior. Smelt and Mysis play a prominent role in sustaining the current trophic structure. Competition between the native lake trout and the exotic salmonids is asymmetric. Reductions in the salmon population yield only a modest benefit for the stocks of lake trout, whereas increased fishing of lake trout produces substantial potential increases in the yields of Pacific salmon to recreational fisheries. The deepwater or siscowet morphotype of lake trout has become very abundant. Although it plays a major role in the structure of the food web it offers little potential for the restoration of a valuable commercial or recreational fishery. Even if a combination of strong management actions is implemented, the populations of lean (nearshore) lake trout cannot be restored to pre-fishery and pre-lamprey levels. Thus, management strategy must accept the ecological constraints due in part to the presence of exotics and choose alternatives that sustain public interest in the resources while continuing the gradual progress toward restoration. Received 10 December 1999; accepted 13 June 2000.     

Changes in the trophic interactions and the community structure of Lake Taihu (China) ecosystem from the 1960s to 1990s

As the third largest freshwater lake in China, Lake Taihu has suffered from overfishing, eutrophication, and physical disturbance over the last several decades. Evaluating and quantifying changes in the ecosystem can help us better understand and develop hypotheses to explain the dynamics of the ecosystem. In this study, trophic interactions and community structure of commercial fisheries species of Lake Taihu ecosystem were analyzed and compared for three time periods (1961–1965, 1981–1987, and 1991–1995) using the Ecopath with Ecosim model with the aim of evaluating the changes in the population dynamics and ecosystem development mechanism spanning the period from the 1960s to 1990s. The results show that the biomass of large predators decreased over the three decades, while the biomass of small species increased. Increases in the P/B ratios and fishing mortality levels observed for species groups reveal rapidly intensifying fishery stress over the three decades. The fisheries operated at the highest trophic level during the 1980s, and there are some indications of “fishing down the food web” in this ecosystem between the 1980s and the 1990s. Drawing upon Odum’s theory of ecosystem maturity, the structured, web-like ecosystem of the 1960s developed into a highly mature system during the 1980s; yet, in the 1990s, this structure became less complex and the system’s maturity fell to its lowest observed level. During this period, the successional development of the system occurred in reverse.     

基于Ecopath模型的太湖生态系统结构与功能分析

根据2008—2009年太湖湖区水生生物调查的结果及主要水生动物摄食生态学已发表资料,应用Ecopath with Ecosim 6.1软件构建了太湖生态系统的食物网模型,初步分析了太湖生态系统功能与结构特征.模型由初级生产者、主要鱼类及无脊椎动物和有机碎屑等20个功能组组成.结果表明： 太湖生态系统的能流主要分布在4个营养级上,顶级捕食者鲌鱼营养级最高.食物网存在两条主要的营养传递途径,即碎屑食物链和牧食食物链,且碎屑食物链占比较大;营养级I的利用效率低下,大量初级生产力未能流入更高的营养层次,造成生态系统下层的营养流动“阻塞”.对系统总体特征分析发现,反映系统成熟度的指标,包括较高的净初级生产力(NPP)和净初级生产力/呼吸(NPP/R),以及较低的连接指数(CI)、系统杂食指数(SOI)和Finn循环指数(FCI)等,都揭示了太湖“幼态化”的生态系统现状;混合营养分析和关键种筛选结果显示,高强度的渔业捕捞活动对系统负影响显著,而顶级捕食者的下行效应显著下降.
     

The rise of potentially toxin producing cyanobacteria in Lake Naivasha,Great African Rift Valley,Kenya

Lake Naivasha, an important inland water ecosystem and a crucial freshwater resource in the Great African Rift Valley, has displayed clear signals of degradation in recent decades. We studied the phytoplankton composition and biomass levels in the period 2001–2013 and noted a progressive increase in the occurrence of potentially toxic cyanobacteria. Analyses for the presence of cyanotoxins such as microcystins (MC), cylindrospermopsin (CYN) and anatoxin-a (ATX-a) were carried out on samples collected in 2008–2013. Among the cyanotoxins tested, low concentrations of MC were detected in the lake. This is the first record of the occurrence of MC in Lake Naivasha. For the first time, molecular phylogenetic investigations of field clones of cyanobacteria from Lake Naivasha were carried out to establish the taxa of the dominant species. Amplification of the aminotrasferase (AMT) domain responsible for cyanotoxin production confirmed the presence of the mcyE gene belonging to the microcystin synthesis gene cluster in field samples containing Microcystis and Planktothrix species. These findings suggest that toxin producing cyanobacteria could become a threat to users of this over-exploited tropical lake in the near future.     

Resident spawning of Japanese smelt,Hypomesus nipponensis,along gravel shorelines in Lake Nojiri,Central Japan

In Lake Nojiri, the Japanese smelt, Hypomesus nipponensis McAllister, 1963, population has been thought to be maintained by artificial spawning, and stocking efforts as natural spawning in in-flowing streams is unlikely due to the lack of inflowing stream habitat. In this study, novel resident Japanese smelt spawning was observed along the lakeshore in shallow areas with clean gravel and flow. Spawning occurred at night during early March to mid-April and eggs, confirmed on gravel substrate, progressed to the eyed state in 5–6 weeks. Although natural spawning was observed, the ratio of eggs that progressed to the eyed stage was minimal, possibly due to thick algae cover in areas with low flow velocity. Therefore, resident Japanese smelt spawning along the lake shoreline is physically possible and potentially contributes to the overall population in Lake Nojiri, but in-lake spawning alone presumably is not a biologically viable method for population sustainability due to low survival rates and egg density at present. Environmental improvements such as construction of fish ladders to suitable in-flowing spawning habitat, introduction of clean gravel to shorelines, and water level management adjusted to the smelt spawning run would contribute to higher recruitment by natural smelt reproduction, and consequently enhance the smelt production in Lake Nojiri.

     

Examination of the effects of largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) on the ecosystem attributes of lake Kawahara-oike,Nagasaki, Japan

The introduction of largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) into the freshwater ecosystems of Japan has resulted in the suppression and/or replacement of native species, generating considerable concerns among resource managers. The impacts of largemouth bass and bluegill on native fauna have been examined in aquaria and isolated farm ponds, but there is limited work examining the likelihood to fundamentally modifying Japan's lakes. The objective of the present study is to examine the direct and synergistic ecological effects of largemouth bass and bluegill on the biotic communities of Lake Kawahara-oike, Nagasaki, Japan, using an ecosystem (Ecopath) modeling approach. Specifically, we examine whether the two fish species have played a critical role in shaping the trophodynamics of the lake. We attempt to shed light on the trophic interactions between largemouth bass and bluegill and subsequently evaluate to what extent these interactions facilitate their establishment at the expense of native species. We also examine how these changes propagate through the Lake Kawahara-oike food web. Our study suggests that the introduction of bluegill has induced a range of changes at multiple trophic levels. The present analysis also provides evidence that largemouth bass was unable to exert significant top-down control on the growth rates of the bluegill population. Largemouth bass and bluegill appear to prevail over the native fish species populations and can apparently coexist in large numbers in invaded lakes. Future management strategies controlling invasive species are urgently required, if the integrity of native Japanese fish communities is to be protected.     

Spatial-temporal characteristics of epilithic algae succession on artificial substrata in relation to water quality in Erhai Lake,Yunnan Province,China

In this study, two sites with different nutritional levels at Erhai Lake were selected to perform an epilithic succession experiment in order to better understand the successional dynamic process and associated controlling factors, providing important insights into the role of epilithon in ecological functions and facilitating eutrophic lake recovery planning. The environmental parameters, epilithic biomass and epilithic diversity were qualitatively and quantitatively assessed. Our results showed that faster biomasses peaks (40–50 days colonization) were achieved at Gusheng where nutrient level was higher, comparing with that of Xiahe. A 10-day incubation period is a dividing line from an initial successional stage to the following stage during epilithon succession. The epilithic biomass and biodiversity exhibited distinctly spatial-temporal characteristics, showing higher values at the site being affected by human activities than that being under the natural condition. The spatial characteristic was associated with nitrate enrichment (the most important), and the positively biological responses of the epilithon (higher biomass and diversity) to nitrate enrichment highlight the occurrence of non-point-source pollution on the west bank of Erhai Lake. The temporal characteristic was associated with water temperature (the second important), exhibiting a high biomass accumulation in winter compared with that in summer. This may be caused by other biotic factors not measured in this study, therefore, a detailed investigation regarding the interactions among biotic components in Erhai Lake is essentially needed.     

Assessment of Top-Down and Bottom-Up Controls on the Collapse of Alewives (<Emphasis Type="Italic">Alosa pseudoharengus</Emphasis>) in Lake Huron

Food web models are powerful tools to inform management of lake ecosystems, where top-down (predation) and bottom-up (resource) controls likely propagate through multiple trophic levels because of strong predator–prey links. We used the Ecopath with Ecosim modeling approach to assess these controls on the Lake Huron main basin food web and the 2003 collapse of an invasive pelagic prey fish, alewife (Alosa pseudoharengus). We parameterized two Ecopath models to characterize food web changes occurring between two study periods of 1981–1985 and 1998–2002. We also built an Ecosim model and simulated food web time-dynamics under scenarios representing different levels of top-down control by Chinook salmon (Oncorhynchus tshawytscha) and of bottom-up control by quagga mussels (Dreissena rostriformis bugensis) and nutrients. Ecopath results showed an increase in the relative importance of bottom-up controls between the two periods, as production decreased across all trophic levels. The production of non-dreissenid benthos decreased most, which could cause decreases in production of pelagic prey fishes feeding on them. Ecosim simulation results indicated that the alewife collapse was caused by a combination of top-down and bottom-up controls. Results showed that while controls by Chinook salmon were relatively constant before alewife collapse, controls by quagga mussels and nutrients increased jointly to unsustainable levels. Under current conditions of low nutrients and high quagga mussel biomass, simulation results showed that recovery of alewives is unlikely regardless of Chinook salmon biomass in Lake Huron, which implies that the shrinking prey base cannot support the same level of salmonine predators as that prevailed during the 1980s.     

竺山湾湖泊缓冲带湿地生态系统EWE模型构建与分析

湖泊缓冲带在湖泊流域空间布局中具有特殊地位,缓冲带内的湿地对于保障流域生态健康和湖泊水环境质量具有十分重要的意义.本研究以太湖竺山湾湖泊缓冲带内的竺山湖湿地生态系统为研究对象,将生物组分划分为16个功能组,构建了生态通道(EWE)模型,并分析了生态系统的特征、状态以及功能组之间的相互关系.结果表明: 竺山湖湿地生态系统的有效营养级范围在1~3.72,营养流动主要发生在前4个营养级,开始于沉水植物和有机碎屑的食物链较多.湿地生态系统的总的能量转换效率为5.1%,并未达到“1/10定律”,说明当前的能量转换效率较低.物质流量在生态系统中的平均传输效率为4.3%.系统的总生产量为2496.66 t·km^-2·a^-1,总流量为10145.2 t·km^-2·a^-1.生态系统的多种特征参数表明当前生态系统处于幼态化阶段.     

The effect of ecological rehabilitation of the Erhai lakeside on Odonata species richness and abundance

Erhai Lake is also called ‘mother lake’ by the residents of Dali in Yunnan Province of western China. Since 2000, a series of ecological restoration projects have been conducted in Erhai lakeside. Here, we studied the changes in species abundance and richness of the order Odonata caused by this ecological restoration. From 2004 to 2016, we sampled adult and larval Odonata in Erhai lakeside and found 4335 individuals, representing 32 species. Results of our study showed that the abundance and species richness of Odonata varied at different sites of this wetland, but Odonata increased after the ecological restoration compared to those in the pristine areas. We suggest that Odonata is an indicator of the changes in the habitat structure of the Erhai lakeside.     

洱海蓝藻爆发的时空特征及影响因子

湖泊生态环境对区域气候变化和流域人类活动十分敏感。随着流域的持续开发,洱海作为云贵高原第二大淡水湖泊面临着严重的生态与环境问题,主要包括水质恶化和生态功能的衰退,其中蓝藻水华问题尤为突出。针对湖泊现代监测数据存在时间序列较短、连续监测记录缺乏、监测位点不完全一致等问题,应用沉积物记录开展色素等多指标分析和环境变化重建研究,并对洱海湖区南、中、北3个湖盆的沉积物记录进行对比分析,从而探讨洱海富营养化与蓝藻爆发的历史与变化特征,并识别藻类响应模式的空间异同。沉积物色素记录结果表明,洱海蓝藻生物量变化具有明显的时空差异性,呈现由南至北,先后增加、最后呈现蓝藻水华全湖性持续爆发的模式。进一步的简约模型方差分解结果表明气候变暖和营养盐富集是洱海蓝藻生物量变化的主要驱动因子,此外相对较浅的南部湖盆还受到水位波动、水动力减弱、水生植物演化的综合影响。因此,在气候变暖的背景下,控制水体营养盐输入、合理调控湖泊水位、提高水体透明度并恢复水生植物是控制洱海蓝藻水华爆发和进行生态恢复的重要措施。     

鲥鯸淀浮游动物群落特征及水质评价

为掌握白洋淀典型湖泊鲥鯸淀浮游动物群落结构及水体营养状况, 于2018年秋季、2019年春季和夏季对该淀的浮游动物群落组成、密度、生物量和多样性进行调查研究, 分析了主要水质理化指标, 运用多变量统计方法分析浮游动群落结构与主要环境因子关系。共鉴定浮游动物3类52种, 其中轮虫类种类数最多, 为33种, 占64.46%。共鉴定优势种23种, 其中15个优势种为轮虫; 浮游动物密度秋季最高, 生物量夏季最高。冗余分析表明, 氨氮、COD和总磷是轮虫群落分布的主要影响因子。综合多样性指数与水质指标评估鲥鯸淀水域处于中度污染状态。研究可为白洋淀生境保护和渔业资源的可持续利用提供科学依据。     

洱海三种生活型水生植物叶片中碳、氮与总酚含量的比较研究

植物体内的C、N和总酚是影响其被牧食和凋落物降解的重要因素,从而影响C和N在食物链的传递和生物地化循环。本研究测定了云南洱海3种生活型（挺水、沉水和浮叶）26种水生植物叶片中C、N和总酚含量以及C/N比率,并分析了它们与总酚的关系。结果表明:挺水植物叶片的C、N和总酚平均含量为448.08、39.30和24.70 mg/g,浮叶植物叶片的C、N和总酚平均含量为433.32、35.16和28.05 mg/g,沉水植物叶片的C、N和总酚平均含量为378.36、27.31和10.28 mg/g;总体上看,植物叶片C和N含量:挺水植物 浮叶植物 沉水植物;挺水和浮叶植物叶片的总酚含量差异不显著,且均远高于沉水植物叶片的总酚含量;26种植物叶片中C和N与总酚含量均呈显著正相关。在富营养化条件下,3种生活型植物所处生境的光照和CO2供给均差异显著,会对这些植物叶片的C、N和总酚含量有一定影响,此外由于应对生境中的胁迫（草食性昆虫、病原体及紫外线辐射等）压力以及自身的生长策略的不同也可能导致C、N和酚在三者中形成差异;通过对13种沉水植物叶片总酚含量比较,推测光叶眼子菜和微齿眼子菜较为适合作为洱海耐牧食恢复先锋物种;N与总酚正相关的关系可能在富营养化进程中加速湖泊沼泽化。     

How important are trophic state,macrophyte and fish population effects on cladoceran community? A study in Lake Erhai

Environmental controls on cladoceran community structure in lake ecosystems are complex and may involve many environmental parameters including trophic state and fish populations. In Lake Erhai, a plateau lake located in southwest China, it was hypothesized that a combination of lake eutrophication and planktivorous fish introduction would increase the abundance of cladoceran, while also decreasing cladoceran size. To test this hypothesis, we examined temporal changes in cladoceran microfossils in the sediments of Lake Erhai over the past century. The influence of changing macrophyte coverage within the littoral region of the lake was also considered. Results demonstrated that cladoceran abundance (measured as flux of cladoceran fossils in the sediments) increased markedly accompanying eutrophication of the lake. In addition, there was a shift in the dominant cladoceran species from those species that prefer oligotrophic conditions to those that prefer mesotrophic and eutrophic conditions. A reduction in the ephippium length of Daphnia spp. was observed and attributed to the introduction of the planktivorous fish Neosalanx taihuensis. Our findings indicated that eutrophication and fish introduction were the main controls affecting cladoceran community structure during the recent decades, and predation by planktivorous fish had an important impact on Daphnia body size.     

保水渔业对千岛湖食物网结构及其相互作用的影响

为预防千岛湖连续暴发了2a(1998—1999)的蓝藻水华和改善千岛湖水质,于2000年起在千岛湖开展了以人工放养鲢鳙和控制凶猛鱼类为主要措施的保水渔业试验。作为试验的主要研究内容之一,通过构建1999和2000年千岛湖生态系统的Ecopath模型,比较分析了实施保水渔业对千岛湖生态系统食物网结构及其相互作用的影响。结果表明:实施保水渔业,使千岛湖中的银鱼和鲤生物量减少,而鲌类(主要是蒙古鲌)、鲴类和大眼华鳊等增加;使各种鱼类的捕食者和食饵生态位重叠指数下降;各主要鱼类的相互作用中,鲢、鳙对鳡、鲌的促进作用增强,鳡对鲌的抑制作用及鲌对虾类、银鱼和鲤等以及银鱼对浮游动物的抑制作用减弱,鳙对银鱼、大眼华鳊对鲤的抑制作用增强。这些影响,使千岛湖食物网结构更趋合理,如底层碎屑食性鱼类如鲴类等的增加,有利于营养物的再循环和再利用,从而增强了水体对营养物的净化作用。