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1.
枝角类作为淡水湖泊生态系统中的初级消费者之一,对生存环境的改变极为敏感.本文分析了太湖西、中和东部等湖区的钻孔沉积物、表层沉积物以及春夏秋季活体枝角类的组成与丰度.结果表明:活体枝角类组成以象鼻溞(Bosmina spp.)为优势种,秋季枝角类属种数量最多.太湖不同生态型湖区表层沉积物枝角类组成均以象鼻溞为优势种,其中西部与中心湖区的枝角类组成与丰度较为相似,种类单一,枝角类绝对丰度高;东部湖区枝角类属种较为丰富,绝对丰度低,优势种由浮游种象鼻溞以及沿岸种圆形盘肠溞(Chydorus sphaericus sl)和西方笔纹溞(Graptoleberis testudinaria)等种属构成.百年以来,太湖枝角类组成与丰度随着营养水平增加而改变,富营养指示种(Bosmina longirostris)丰度的增加与贫营养指示种(Bosmina longispina)丰度的下降,响应了湖区生态环境的演变过程.1970s末期,太湖西部与中心湖区在进入富营养化阶段,枝角类组成单一,象鼻溞占有绝对优势,与东部湖区相比,沿岸种、底栖种稀少.东部湖区在1960s以后,枝角类属种数量增加,但丰度下降,响应了1960s以来该区域营养水平提高、沉水植被生物量增加以及沼泽化加剧的环境过程. 相似文献
2.
从1950s开始, 云南地区部分湖泊受到了水文调控(如筑坝)和鱼类引入等流域开发活动的直接影响, 湖泊水环境与生态系统结构已出现明显改变. 开展浮游动物群落的长期生态响应评价有助于认识气候波动和人为胁迫的影响模式. 本文选取云龙天池进行了沉积物记录分析, 在重建过去100年环境变化历史的基础上开展了枝角类群落的多指标分析(物种组成、个体大小、生物量等), 进一步结合多变量分析识别了枝角类群落构建的关键驱动因子. 结果显示, 云龙天池在过去100年间经历了明显的水位波动, 约1962年以前水位较低, 1950s起的水文调控(筑坝)导致湖泊水位波动上升, 2006年以来略有下降. 枝角类群落随水位波动呈现由底栖种向浮游种占优转变的模式, 并在2006年以来底栖种略有增加. 总体上, 低水位时期底栖枝角类占优, 高水位时期浮游枝角类占优. 水体营养水平也对枝角类群落产生了较为显著的影响. 在沉积物总氮和有机质通量上升时, 长额象鼻溞(Bosmina longirostris)相对丰度和枝角类浓度都明显上升. 枝角类象鼻溞个体大小表明, 1969年鱼类引入后象鼻溞的壳长、壳刺长度、触角长度显著减小, 反映了鱼类捕食压力上升的影响. 本研究进一步揭示了水文调控和鱼类引入对湖泊环境和生物群落结构的驱动影响. 其中, 1960s以前云龙天池处于自然波动的状态, 湖泊环境和枝角类群落变化主要受气候(如降水、气温)的影响; 1960s以来人类活动的影响强度已经掩盖了气候变化的信号, 成为影响湖泊生态演化轨迹的主要因素. 为了开展有效的湖泊保护与生态治理, 有必要综合评估水文调控、鱼类引入等人类活动对湖泊生态健康的长期影响. 相似文献
3.
高山湖泊吉仁错位于川西高原树线以上,受现代冰川融水补给影响.通过吉仁错沉积钻孔~(210)Pb/~(137)Cs定年和沉积枝角类和多环境代用指标分析,结合主成分分析和冗余分析等方法,高分辨率重建了近200 a来吉仁错枝角类组合和环境变化的过程.结果表明,尽管过去200 a来吉仁错枝角类组合一直以沿岸种为主,但仍经历了3个明显的变化阶段.1850 AD后,枝角类组合中Alonella nana、Chydorus sphaericus和Pleuroxus sp.的增加、以及Alona rustica和Alona guttata丰度的下降指示了水温和水体pH值的上升.1900 AD后枝角类通量的增高并不同步于组合的变化,指示了湖泊营养开始增加,这种不一致的变化分别代表了大气氮沉降和区域气候变暖的影响结果.多指标综合分析得出,过去150 a来,气候变暖和大气污染沉降通过直接和间接作用(流域冰川融水过程和植被土壤过程),较深刻地影响了湖泊物理过程(水温升高和无冰期加长)、营养过程(氮、磷营养升高)和酸碱平衡过程(碱性增强),改变了湖泊生物的生长季节,并通过促进藻类发育,最终引起了湖泊枝角类群落组合的变化和生物量的增加.1945 AD前后吉仁错枝角类与藻类群落结构和湖泊环境的同步变化,响应于持续增温背景下多环境过程的相互作用. 相似文献
4.
Zooplankton response to the lake restoration in the drinking-water source in Meiliang Bay of subtropical eutrophic Lake Taihu, China 总被引：1，自引：0，他引：1
A 3-year ecological engineering project was carried out from 2003 to 2005 in the drinking water source in Meiliang Bay, Lake Taihu, China. The project area was divided into three zones: Zone C (outside the area), Zone B (pelagic part within the area) and Zone A (littoral part within the area). The community composition, density and biomass of zooplankton were studied as a part in the lake restoration study. Also, the abundance, biomass and composition of fish in the engineering area were annually analyzed in the littoral zone (Zone A). The average density of cladocerans decreased from the outer part to the inner part of the lake, i.e., from Zone C to Zone A, while the average density of copepod did not significantly vary among the 3 zones. The average densities of rotifer and ciliate increased from Zone C to Zone A. RDA analysis indicated that Microcystis biomass more impacted the zooplankton compositions after temperature. In Zone A, many planktivorous fishes, e.g., Coilia nasus, Hemiculter leucisculus, Pseudorasbora parva, dominated the fish community, which caused a marked decrease in the abundance of cladocerans, especially large-sized cladoceran Daphnia galeata and Daphnia obtusa. Our results suggested that both fish predation and other environmental factors such as the Microcystis bloom greatly affected the zooplankton community during the restoration of subtropical eutrophic lakes. 相似文献
5.
Dietmar Straile 《Limnologica》2010,40(2):92-96
The long-term dynamics of the cladoceran Bosmina spp. were analysed in Lake Constance during the study period 1979-1998. During this period the lake ecosystem has been influenced strongly by changes in nutrient inflow (oligotrophication) and by climate variability associated with the North Atlantic Oscillation. Bosmina abundances declined strongly during the study period presumably as an indirect consequence of the reduced P loading of the lake. A detailed seasonally resolved analysis of Bosmina dynamics revealed that its abundance decline occurred throughout the year with the exception of the spring period. The lack of a population decline during spring may be attributed to the seasonal absence of the factor, e.g., food limitation and/or predation control by invertebrates causing the population decline. Additionally, climate variability had its strongest influence on Bosmina dynamics during spring and large climate-associated variability of Bosmina may have decreased the power to detect a significant reduction in spring Bosmina abundances with oligotrophication. However, when we account for the confounding influence of climate variability, the effects of oligotrophication are revealed more clearly also during the spring period. Likewise, the detectability of the influence of climate variability on spring Bosmina dynamics increases when accounting for the reduction of abundances in the course of oligotrophication. 相似文献
6.
近几十年来,以大型湖泊为代表的云南部分湖泊受人类活动的持续影响出现了生态环境的明显变化.洱海作为云南面积第2大淡水湖泊,经历了多重环境压力(富营养化、外来鱼类引入、水生植被退化等)的影响.在湖泊现代监测数据面临时段较短、缺乏连续记录的背景下,湖泊沉积物的连续记录可以提供湖泊生态环境变化的长期历史并可用于生态响应模式的识别.以目前处于富营养水平的洱海为研究对象,应用湖泊沉积物记录进行多指标分析,探讨多重环境压力影响下洱海枝角类群落的长期变化特征以及影响因素,并与已有研究成果和现代监测数据进行对比,探讨了枝角类群落对环境压力响应的空间差异性.通过分析沉积物枝角类记录,重建了近百年来洱海枝角类群落的变化历史,结果表明过去100年来,枝角类的生物量总体呈增加趋势,尤其从1990年左右开始,象鼻溞生物量显著增加,物种相对组成出现明显变化(如Bosmina longispina被B.longirostris取代).同时象鼻溞的生物量、壳长与触角长度在1990s初期有明显降低的趋势,与同期外来鱼类(如银鱼)引种成功的时间一致.限制性聚类分析结果表明,枝角类群落结构的变化有3个主要阶段:1990s以前,底栖枝角类为群落的主要组成;1990—2000年左右,浮游枝角类(以象鼻溞为主)在枝角类群落结构中的比例迅速增加;从2000年以后,枝角类群落组成以浮游枝角类为主.同时,枝角类数据的主成分(PCA)分析显示,仅有PCA主轴1呈现显著的变化且解释了群落结构变化的61.64%,进一步分析表明水生植被变化可能是驱动枝角类变化的主要环境梯度,如底栖枝角类生物量减少响应了湖泊水生植被的退化.与已有研究对比表明,浅水湖区沉积物记录的枝角类生物量在1970s急剧增加与1980s急剧降低等现象并没有被深水区的沉积物记录所反映,指示了洱海生态系统的变化模式存在空间差异性.同时象鼻溞个体大小的变化模式反映了外来鱼类引入导致的鱼类捕食压力的变化.总之,本文揭示了枝角类群落结构与生物量的长期变化,反映了洱海富营养化过程、水生植被的退化与外来鱼类引入的长期驱动影响,因此对洱海的生态管理与修复工作应考虑多个环境压力的影响并加强对湖泊生态系统的评价. 相似文献
7.
区域增温和大气氮沉降作用已成为高山湖泊面临的重要环境胁迫,已有高山湖泊生物群落响应的长期模式研究主要集中于藻类而缺乏更高营养级生物(如浮游动物)的系统调查。本研究选择滇西北地区深水型的高山湖泊沃迪错开展沉积物调查,通过多指标分析(总氮、总磷、叶绿素a、氮稳定同位素等)并结合区域气候重建记录,识别近两百年来该湖泊及流域环境的变化历史,进一步利用枝角类群落指标(物种组成、生物量等)定量评价了湖泊生物群落的响应模式与驱动因子。结果表明,湖泊营养水平(如总氮浓度)和初级生产力(叶绿素a浓度等)在过去近两百年总体呈上升趋势。相关分析显示,大气氮沉降和流域外源输入是影响总氮上升的主要因素,同时区域增温和营养盐富集促进了湖泊初级生产力的不断上升。自1960s以来区域升温明显,湖泊营养水平和叶绿素a浓度呈现加速上升的趋势。钻孔中枝角类群落以浮游属种(Daphnia longispina等)为优势种,在1900AD以前D.longispina相对丰度较为稳定(40.83%±8.02%),之后出现下降趋势且在1948—1965年间明显下降,之后再次明显上升并成为主要优势种。排序分析显示,气温、叶绿素a和总... 相似文献
8.
太湖贡湖湾鲚(Coilia ectenes taihuensis Yen et Lin)食物组成的季节变化 总被引：1，自引：1，他引：0
鲚(Coilia ectenes taihuensis Yen et Lin)是太湖主要的鱼类之一,其产量随水体富营养化程度的加重呈上升趋势.本研究于2009年4-12月用刺网(a=10 mm)在太湖贡湖湾采集了鲚,分析了其胃含物中食物组成的季节变化以及鲚对食物种类的选择性.结果表明,鲚在各月中主要以浮游动物为食,同时也摄食幼鱼、幼虾和水生昆虫等.鲚的食物组成具有明显季节变化,4月份以桡足类为食,其中桡足幼体、汤匙华哲水蚤(Sinocalanus dorrii Brehm)和剑水蚤(Cyclops spp.)所占的平均个数百分比相当;6、8和10月份主要以枝角类为食,其中6月以裸腹溞(Moina spp.)为主,而8和10月以象鼻溞(Bosmina spp.)为主.食物选择性方面,鲚对大型浮游动物表现出主动选择;当环境中出现溞(Daphnia spp.)和透明薄皮溞(Leptodora kindti Focke)时,鲚对它们表现出很强的选择性摄食,但透明薄皮溞只出现在6月鱼类食物中;个体较小的裸腹溞也是鲚主动选择的重要食物,在整个调查期间鲚对裸腹溞都表现出较高的主动选择性;象鼻溞虽然在各月份食物中的出现率最高,但除10月份鲚对其表现出主动选择外,其它月份表现为主动回避或随机选择.本研究结果有助于我们了解鲚对浮游动物群落影响的季节变化,为制定合理的湖泊与渔业管理方案提供依据. 相似文献
9.
Cladocera remains, organic matter, nitrogen, chlorophyll derivatives have been examined in the sediments to follow the trophic
evolution of Lake Como. Trophic levels result to be increased in these last ten years in the four basins considered;Bosmina remains register recent and significant increases everywhere, whileSida, Acroperus, Daphnia andChydorus seem to disappear or on the strong decrease at present in the southern basins, more subject to the human pressure. Correlation
coefficients are highly significant among organic matter, nitrogen, chlorophyll derivatives and Cladocera remains, giving
stronger evidence for the strict interdependence among nutrients, producers and consumers. 相似文献
10.
抚仙湖浮游甲壳动物群落结构与空间分布 总被引：4，自引：3，他引：1
云南抚仙湖是我国典型的高原深水湖泊,为揭示湖中浮游甲壳动物对生态系统变化的响应,研究了其群落结构与空间分布特征.2005年6-7月在抚仙湖共采集浮游甲壳动物8种,平均密度为27.6ind./L,优势类群为桡足类.桡足类优势种为舌状叶镖水蚤(Phyllodiaptomus tunguidus Shen et Tai),枝角类优势种为角突网纹涵(Ceriodaphnia cornuta Sars)和象鼻溞(Bosmina sp.).浮游甲壳动物主要分布在0-30m水层,密度随水深增加而下降;0-10m水层,枝角类和无节幼体占优势,大于10m水层,桡足类占优势.浮游甲壳动物密度南区大于北区(P<0.01),而沿岸区与湖心区之间、沉水植物区与非沉水植物区之间无显著性差异(P>0.05).相关分析表明:浮游甲壳动物密度的垂直分布与藻类密度和水体理化凼子相关关系显著,而水平分布与藻类密度和水体理化因子相关关系不显著.与20世纪80年代相比,抚仙湖浮游甲壳动物优势种发生了演替,西南荡镖水蚤(Neutrodiaptomus mariadviagae mariadviagae (Brohm))消失,被舌状叶镖水蚤代替,可能与太湖新银鱼(Neosalanx taihuensi Chen)引入有关;浮游甲壳动物密度表现出增加趋势,但仍处于较低水平,与水体营养水平的提高及太湖新银鱼的捕食压力有关. 相似文献
11.
《Limnologica》2014
Andean Patagonian lakes are ultraoligotrophic and deep, have simple food webs and low fish diversity and abundance. In this work the distributional abundance data of fish was studied in two interconnected Andean Patagonian lakes with varying proportions of contrasting habitat types. Hydroacoustic data (120 kHz) were used to analyze fish abundance and habitat use during the mixis and stratification periods. Three types of habitat (near shore, surface pelagic and deep pelagic) and two groups of fish, based on size (Big Fish >12 cm total length and Fish Larvae and Small Fish <12 cm total length) were defined. The distribution of both fish groups in these lakes revealed differences in habitat use for each lake and period. Fish group abundance was related to the availability of habitat types, according to the morphology of each lake. The Big Fish group showed preference for the near shore habitat during lake stratification and always appeared as individual targets. The Fish Larvae and Small Fish group used mainly the pelagic habitat during mixis, where they formed dense sound scattering layers. However, during lake stratification many individual targets from this group were found both in pelagic and near shore habitats, which would seem to indicate a change in distributional behavior. This is possibly associated with niche changes in the Galaxiids (Galaxias spp), a key component of Northern Patagonian lake food webs. Lakes like Moreno Oeste, which are morphologically and structurally more complex, could have more diverse fish ensembles with higher abundances. In contrast, lakes of simple morphology with low development of near shore habitats and ample deep zones, like Lake Moreno Este, could present lower Big Fish abundance. The contrasting habitat availability between lakes accounts for the abundances and distribution patterns of each fish group. While in these lakes fish assemblage species composition could depends on the environmental filter, the particular structure of a fish assemblage in terms of the proportional abundances of species depends on proportional habitat type availability. We can speculate that in Andean Patagonian lakes Galaxiids mediate a habitat coupling process critical for the transfer of energy and matter in oligotrophic lakes. We may also consider that the Small Puyen in this type of lake is a keystone prey species that relieves predation pressure on other potential prey. The existence of deep pelagic habitats in numerous deep lakes in the Northern Patagonian Andean region provides not only daytime refuge for Galaxiids, which allows them to maintain their high numbers in the lakes, but could also, in the long term, act as a Galaxiid source for other water bodies. 相似文献
12.
热带浅水湖泊后生浮游动物群落结构对生态修复的响应 总被引：5，自引：4，他引：1
热带浅水湖泊后生浮游动物群落以轮虫和小型枝角类为主,往往缺乏大型浮游动物,其影响因子还存在争议,因此通过减少鱼类,提高大型后生浮游动物密度,从而增强对浮游植物的下行控制、修复热带富营养化湖泊的方法受到质疑.暨大南湖位于广州暨南大学校园内,是热带富营养化浅水湖泊,于2014年1—2月实施以鱼类去除和水生植被重建为主的生态系统修复工程,以期改善水质.通过对南湖修复前后水质、后生浮游动物以及修复后鱼类群落的调查分析,研究了后生浮游动物群落对修复的响应.结果表明:与修复前相比,总氮、总磷和叶绿素a浓度显著降低,透明度显著上升.枝角类丰度和生物量显著增加,修复后初期出现较高密度的大型枝角类蚤状溞(Daphnia pulex),桡足类丰度和生物量没有显著变化,轮虫丰度下降而生物量上升;后生浮游动物体长和生物多样性显著增加.随着鱼类密度的增加,蚤状溞丰度快速降低,后期鱼类减少后蚤状溞丰度又有所升高.因此,本研究显示鱼类是控制热带浅水湖泊大型浮游动物种群的主要因素,由于控制鱼类密度以维持较高大型浮游动物密度较为困难,因此单纯生物操纵在热带浅水湖泊修复中难以取得显著效果. 相似文献
13.
This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 108 L?1. The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations of the pH affected the plankton community and reduced its species diversity. 相似文献
14.
近百年来长江中下游地区的浅水湖泊经历了气候变化及日益增强的人类扰动,造成了普遍的湖泊富营养化、水动力条件和水生生态系统的状态转变,水体的生态服务功能明显退化.枝角类作为一种重要的水生生物,敏感地响应于湖泊及其流域的环境变化,但目前对亚热带湖泊中的枝角类亚化石的环境指示意义,与其它古生态指标如硅藻、摇蚊等对环境变化的响应差异尚未明确.因此,本文以浅水湖泊太白湖为研究对象,结合流域历史资料和监测数据,基于沉积岩芯中枝角类群落过去百年来的期演化序列,重建了近百年来太白湖的历史环境演变过程及机制.对比硅藻及摇蚊的群落演化特征,探讨了多门类古生态指标对环境变化的响应差异.本文重点讨论了枝角类对湖泊鱼类产量指示意义及利用枝角类亚化石来重建历史环境的应用前景及不足. 相似文献
15.
沉积物再悬浮对食浮游动物鱼类捕食浮游动物的影响 总被引：3，自引：2，他引：1
在亚热带浅水湖泊中,由风浪引起沉积物再悬浮是其重要特征之一.沉积物再悬浮一方面直接影响浮游动物群落结构,另一方面通过影响食浮游动物鱼类对浮游动物的捕食而产生间接影响.以食浮游动物鱼类——餐条(Hemiculter leucisculus)为实验对象,通过模拟实验,比较不同再悬浮条件下餐条对浮游动物群落结构的影响.结果显示,在有餐条的处理组中,大型枝角类短钝溞(Daphnia obtusa)只在弱再悬浮条件下出现,并成为枝角类群落的优势种;在无餐条的处理组中,短钝溞生物量随再悬浮强度减弱而增加.强再悬浮(无餐条)和无再悬浮(有餐条)条件下,小型枝角类角突网纹溞(Ceriodaphnia cornuta)和盘肠溞(Chydorus sp.)为优势种.无论有、无餐条条件下,桡足类优势种均为中剑水蚤(Mesocyclops sp.),其生物量随再悬浮强度减弱而增加.所有处理组中,轮虫丰度均低于枝角类和桡足类丰度.研究表明,在亚热带浅水湖泊中,适当的悬浮质浓度既能干扰食浮游动物鱼类对大型浮游动物的捕食,又不影响大型浮游动物的生存,使得它们保持一定的丰度,通过对浮游植物的摄食,降低叶绿素a浓度. 相似文献
16.
三峡水库以及上游江段形成的河—库生态系统与长江中下游洞庭湖和鄱阳湖的江湖生态系统都是四大家鱼的重要栖息地,有相似性也有差异.2017年7—8月在三峡水库、洞庭湖和鄱阳湖利用地笼、虾笼、高网和迷魂阵采集草鱼和鲢幼鱼样本,观测耳石日轮,分析三峡水库和通江湖泊草鱼和鲢幼鱼的繁殖时间和早期生长特征及差异,探讨相应的保护措施.结果显示,三峡水库、洞庭湖和鄱阳湖采集草鱼幼鱼的孵化日期分别为4月24日—5月25日、5月21日—6月26日和5月4日—5月28日;鲢幼鱼的孵化日期分别为4月10日—6月12日、5月25日—6月19日和5月9日—6月12日.三峡水库、洞庭湖和鄱阳湖草鱼样本的体长增长率分别为1.04、1.84和1.64 mm/d,微耳石的沉积率分别为3.41、5.41和4.77μm/d;鲢幼鱼的体长增长率分别为1.10、2.87和1.96 mm/d,微耳石沉积率分别为2.96、7.17和4.57μm/d.洞庭湖草鱼和鲢的体长增长率和耳石沉积率均显著大于三峡水库;鄱阳湖鲢的体长增长率和耳石沉积率均显著大于三峡水库,而草鱼的体长增长率和耳石沉积率则与三峡水库没有显著差异.结果表明,三峡水库蓄水后长江中游干流草鱼和鲢的繁殖时间明显滞后;洞庭湖和鄱阳湖的草鱼和鲢幼鱼生长更快.目前,长江全面禁渔正在逐步实施,预期将对恢复鱼类资源起到重要的作用.除了全面禁渔之外,还建议保护和修复鱼类栖息地;减少江湖阻隔,灌江纳苗;增殖放流亲鱼;开展生态调度,促进鱼类繁殖. 相似文献
17.
《Limnologica》2017
Acid deposition during the 20th century led to the gradual elimination of fish in Brooktrout Lake (Adirondack Mountains, New York State). Thereafter, the lake was colonized by Chaoborus americanus, a dipteran with an aquatic larval stage that typically resides in the pelagic zone in fishless lakes. During subsequent chemical recovery from acidification, the lake was stocked with Brook Trout (Salvelinus fontinalis). For seven years following this reintroduction we examined the re-adaptation of the food chain. The C. americanus abundance and distribution was quantified utilizing a combination of hydroacoustics, traditional vertical net tows and Schindler-Patalas trap collections. Hydroacoustic backscattering signals were repeatable and correlated (r = 0.86, p = 0.003) with C. americanus abundance. Backscattering, depth, month and year were used to develop a random forest model that predicted the C. americanus density (r2 = 0.67, p< 0.05). The hydroacoustic signal revealed a clear but limited diurnal vertical migration of C. americanus. The signal continued in the presence of the fish population beginning with reintroduction in 2005 and extending through 2011. In 2012, the hydroacoustic signal no longer was present in the lake, suggesting that the fish had eliminated the C. americanus population, which was verified with net tows. Using novel and traditional survey methods, we demonstrate that the reintroduction of fish can alter the lake community structure significantly through the extirpation of the major component of the pelagic zone. 相似文献
18.
大型通江湖泊洞庭湖的鱼类物种多样性及其时空变化 总被引：12，自引：3，他引：9
为了解通江湖泊鱼类物种多样性现状,于2004年3月-2004年12月和2005年5月对洞庭湖城陵矶、岳阳和沅江三个区域的鱼类进行逐月调查.共鉴定鱼类69种,隶属6目14科44属,其中59.4%为鲤科鱼类.以种类数和多样性指数分析了群落多样性特征,结果表明洞庭湖鱼类种类多样性较高,且时空变化较大.一般地,湖区与长江干流的距离越近,种类数达到峰值的时间就越早;鱼类多样性在春夏季高于秋冬季,在南洞庭湖高于其它两个区域.以优势度>5000为标准,全湖有17种优势种,其中80.0%为湖泊定居性鱼类.在生态类群方面,湖泊定居性鱼类种类最多,占总种类数的74.0%;江湖洄游性鱼类最少,占13.0%.对比分析显示,由于生境丧失、天然苗种资源衰退和过度捕捞等原因,洞庭湖鱼类多样性较20世纪70年代明显下降,洄游鱼类种类数减少;通江湖泊鱼类多样性明显高于阻隔湖泊,表明江湖阻隔造成鱼类多样性下降,因此,加强江湖连通是保护鱼类多样性的有效手段. 相似文献
19.
《Limnologica》2021
Fish assemblage structure in Palair reservoir, a medium tropical reservoir along the river Paleru, a tributary of river Krishna in Southern India, was studied along the spatial gradient of the impoundment. The abundance and assemblage structure of wild fish aggregated around the fish cage units installed in the reservoir were assessed and compared with other sites. Seasonal sampling was carried out and fish community structure in terms of species composition and abundance, trophic guild, niche, tolerance, resilience and conservation status were analyzed. A total of 38 fish species were recorded wherein the family Cyprinidae dominated in the number of species (15) followed by Cichlidae and Channidae (3 each). Margalef richness index (d), Pielou’s evenness index (J’), Simpson’s index (1-λ) and Shannon index (H’) revealed significant variation across different zones. Species richness was maximum in the Site1 (d = 4.44–5.12), whereas the abundance of individuals was maximum at Site4 (H’ = 2.65–2.86) i.e. near cage in the lacustrine zone. The important species contributing to the dissimilarities among the zones were identified and percentage of their contribution was estimated using SIMPER analysis. Trophic guild of fishes indicated the dominance of omnivorous species followed by carnivores, indicating the heterotrophic phase of the reservoir. The spatial and seasonal variations in the fish assemblage structure were tested applying statistical analyses such as PERMANOVA and nMDS. The results indicated a positive impact of cage farming in supporting the wild fish fauna, influencing the large aggregations of fishes around the cages. The temporal variability in the cage-associated fish assemblage was related to recruitment periods of juveniles (e.g. E. maculates and E. suratensis in summer, and S. seenghala in monsoon seasons). The links between fish assemblages and environmental parameters were explored through DISTILM and the deterministic factors for fish abundance in the reservoir were phosphate, pH, dissolved Oxygen, total hardness and depth. The study also indicated the impacts of cage culture with record of accidental escapes of farmed fish to the reservoir system. The baseline information generated and recommendations formulated in the study are crucial for the conservation of fish diversity, fisheries enhancement and management planning of tropical peninsular reservoirs. 相似文献
20.
J.M. Rodriguez C. Gonzalez-PolaA. Lopez-Urrutia E. Nogueira 《Continental Shelf Research》2011,31(14):1462-1473
During summer, wind driven coastal upwelling dominates in the Central Cantabrian Sea (southern Bay of Biscay). Nevertheless, atmospheric forcing is highly variable and wind pulses may cause noticeable and fast hydrographic responses in the shelf region. In this paper, the composition and vertical distribution of the summer ichthyoplankton assemblage during the daytime at a fixed station, located on the Central Cantabrian Sea shelf, are documented. Also, the impact of a short-time scale hydrographic event on the abundance and structure of the larval fish assemblage is examined. Significant small-scale temporal hydrographic variability was observed. Currents showed changes in speed and direction and significant changes in thermocline depth were also observed. A total of 34 taxa of fish larvae were identified. Engraulis encrasicolus eggs and larvae of the shelf-dwelling species Trachurus trachurus, Capros aper and E. encrasicolus dominated the ichthyoplankton assemblage. The distribution of E. encrasicolus eggs and fish larvae was vertically structured. E. encrasicolus egg concentration increased exponentially towards the surface. Fish larvae showed a subsurface peak of concentration and their vertical distribution was not conditioned by thermocline depths. The short term hydrographic event did not affect the vertical distribution of fish larvae but it accounted for significant temporal changes in larval fish assemblage structure and abundance. Results suggest that temperature and light intensity are important factors in the vertical distribution of fish larvae. They also indicate that the temporal monitoring of the larval fish assemblage in this region requires multiple sampling sites. 相似文献