伊乐藻等几种沉水植物的生物量和生产量测定以及竞争态势试验

对1993—1995年在东太湖边池塘中进行的伊乐藻等几种沉水植物的生物量、生产量测定以及竞争态势试验结果进行了分析,阐明了因收割方法不同,水草的单位面积产量及营养物质量不同;并以中位刈割方法为最佳;在竞争试验的环境条件下伊乐藻是优势种。     

前言

“水生植被的恢复与伊乐藻—草鱼圈养人工复合生态系统建设”是中国科学院“八五”重大应用研究项目“海湾、湖泊水产农牧化及生态调控技术研究”的专题,是由中国科学院南京地理与湖泊研究所承担,朱松泉研究员任子专题负责人。经十多位研究人员五年的努力,圆满地完成了任务,达到了合同规定的研究目标,并于1996年2月在武汉通过了中国科学院主持的鉴定与验收。     

伊乐藻对草鱼圈养区环境的影响

通过人工围隔内伊乐藻种植区、无草区和围隔外湖区对照点的水质,底质定期观测,研究了伊乐藻对围栏养鱼环境的影响。结果表明:(1)围栏养鱼残饲和排泄物增加了水中N、P和COD含量,使DO与pH值降低,但伊乐藻对N的净化能力较强,使种植区TN和ION比无草区低14.5％和33.1％;(2)围栏养鱼对底泥的影响,无草区无明显变化,伊乐藻种植区养鱼前期N、P、C含量均低于本底值,养鱼后期有明显的增加趋势;(3)据N、P投入、输出计算,输出和迁移至伊乐藻与鱼体的大于投入的,计算表明,在伊乐藻生长旺季,养鱼与种植面积之比为1:3.58时,不会增加水中N、P含量。(4)养殖水体稀释扩散试验结果,在有草水体中围栏养殖水体对环境影响不大。     

浅水草型湖泊除草技术的实验

滆湖位于江苏南部,面积为164km~2,是一个典型的草型湖泊,其中80X以上的面积为黄丝草(Pataraogeton maackianus)所覆盖。针对该湖水生植被中草食性鱼类喜食性水草资源逐渐衰竭,非喜食性水草群落逐渐扩张的状况,1988—1990年,进行了湖泊水草群落的定向改良试验和抑制相关水草发生和蔓延的试验。结果表明,采用生物防治,以鱼除草,无论是网拦放牧式除草技术,还是网围养殖式除草技术,对各种沉水植物都可彻底清除,而且直接将水草转化为鱼产品,并且有利于湖泊水域生态环境的改善。     

保安湖沉水植被恢复及其渔业效益

通过消除对沉水植物生长有破坏作用的草食性鱼类和杂食性鱼类,在低水位的早春选择无风浪的天气移栽水草,于１９９年保安湖一个面积为３．３ｈｍ＾２网栏湖汊成功地恢复了绝迹８个月的水草群落,秋季水草覆盖盖达５０％,同时研究了在无鱼类摄食破坏的条件下苦草和黄丝草的生长动态。     

沉水植物苦草(Vallisneria natans)对多环芳烃污染沉积物的修复作用

沉水植物是浅水湖泊生态系统的关键种群,对水环境质量及水生生态系统结构有重要影响.以东太湖大水港和湖湾区2个典型的具有不同污染程度的沉水植物苦草(Vallisneria natans)生长区域为研究对象,考察苦草对多环芳烃(PAHs)的修复效果.结果表明,经过34 d植物修复试验,重度污染的东太湖大水港沉积物中PAHs的去除率为62%,沉积物中PAHs降解速率为0.024 d-1;而中度污染的东太湖湖湾区沉积物的PAHs去除率为42%,其降解速率为0.015 d~(-1).种植苦草的沉积物中PAHs的降解速率是未种植苦草的降解速率的2~3倍.苦草对沉积物中高分子量PAHs的修复效果尤为显著.因此,苦草可以有效地用于PAHs污染沉积物的修复,尤其是在重污染和高分子量PAHs污染沉积物中,苦草的修复作用更加明显.     

太湖渔业资源现状(2009-2010年)及与水体富营养化关系浅析

根据2009-2010年的太湖鱼类资源调查,结合历年渔业资料和水环境监测数据,分析太湖渔业资源的发展趋势和结构特征.结果表明:本次调查共采集到鱼类47种,隶属10目14科37属,原常见鱼类种类数明显减少,鲤科等定居性鱼类成为主体;同时,太湖渔业产量近年来增长迅速,渔获物中湖鲚等小型鱼类比重增加,渔业资源的单一化和小型化趋势加剧.根据湖泊水体环境特征的空间差异,对太湖东部湖区、北部湖区和湖心区3个不同类型湖区间的渔业资源特征进行比较.其中在北部湖区和湖心区,浮游食性的湖鲚成为绝对优势种,2008年其产量分别占湖区总产量的70.7％和80.4％,其他主要鱼类所占比重仅为0.2％ -3.0％;而东部湖区草食性和肉食性鱼类的比例较高,鱼类结构相对合理,不同湖区间渔获物的组成差别反映出湖区鱼类组成与环境特征相适应的特点.针对太湖渔业资源与水体富营养化关系进行探讨,提出需加强渔业与湖泊环境功能之间关系的研究,重视水生植被在太湖渔业可持续发展中作用的建议.     

东太湖围网拆除前后水生植被群落遥感监测及变化

为削减东太湖养殖污染,改善湖泊水质,苏州市于2018年底基本完成东太湖养殖围网拆除工作.围网拆除后,湖泊生态环境对此如何响应,已成为学者及相关管理部门关注的重点.水生植被在维持湖泊生态系统平衡、物质循环和净化水质方面发挥着重要的作用,是诊断湖泊生态系统健康状态的关键指标.本研究基于Sentinel-2卫星数据,利用分类决策树模型和基于生活史的沉水植被优势种群提取方法,监测了东太湖2017年(围网拆除前)和2019年(围网拆除后)的水生植被类群和沉水植被优势种群的空间分布.经验证,水生植被类群监测精度为82.66%,Kappa系数为0.77;沉水植被优势种群的监测精度为62.08%,Kappa系数为0.56.结果表明:围网拆除后,东太湖水生植被优势类群由围网拆除前的沉水植被转变为浮叶植被;沉水植被分布面积减少,且种群由优势度相差不大的七大优势种群逐步向菹草和伊乐藻占据绝对优势发展,逐渐趋于单一化.     

太湖鱼类放流增殖的有效数量和合理结构

根据2006-2007年太湖生物资源调查,估算出太湖浮游植物、浮游动物、底栖动物和水生植物总渔产潜力约为78494 t.太湖实施以渔改水的生物调控措施,应加大鲢、鳙放流数量和放流规格,在提高鱼产量的同时对抑制太湖蓝藻水华能起到积极作用;推算每年放流鳙约1000×104尾,鲢约300×104尾,规格为20尾/kg为宜.草鱼、团头鲂、青鱼、鲤等要在保护太湖水草和底栖动物资源和生物多样性前提下适当放流,每年宜放流草鱼150×104尾,团头鲂165×104尾,青鱼8×104 ～ 10×104尾,鲤夏花2500×104尾.而对调控鱼类结构小型化、单一化具有重要作用的肉食性鱼类翘嘴铂建议加大放流量,年放流量可扩大至500×104尾左右,在调控的同时提高湖泊渔业附加值.     

伊乐藻等水生高等植物的快速营养繁殖技术和栽培方法

在太湖自然条件下,伊乐藻等7种沉水植物主要靠营养繁殖来延续和扩大种群。在浅水湖泊的生态恢复中,需要在短期内大面积恢复水生植被,营养繁殖与栽培为之提供了有效的手段。在五里湖的实验研究结果表明,伊乐藻、黑藻和金鱼藻的插枝繁殖简单易行,可以大面积操作,种源充足,栽植期长,适合于大规模繁殖和栽培。苦草、微齿眼子菜和马来眼子菜营养繁殖力较差,可以分苗移栽,但效率较低,操作比较困难。苦草地下块茎和马来眼子菜根状茎的采集和栽植更加困难,不宜采用这种繁殖与栽培方式。     

东太湖养殖渔业可持续发展的思考

东太湖是长江中下游典型草型湖泊,渔业资源丰富,水质良好,具有渔业、泄洪、供水等重要功能,作为我国最早开始网围养殖等养殖业开发的湖泊之一,在促进我国湖泊渔业的发展等方面起到了重要作用,但是养殖渔业的快速发展也带来了一定的负面影响,影响了湖泊渔业等的持续发展,本文以东太湖作为我国浅水湖泊的典型代表,在分析其主要资源及环境特征的基础上,重点分析网围养殖与环境之间的关系,剖析养殖渔业存在的主要问题,提出了相应的湖泊渔业养殖承载力资源环境模型,并就未来湖泊渔业发展提出建议。     

于桥水库的水质保护与渔业生产

大水面增养殖将水体中的氮、磷、有机物转化成鱼产品,并以渔获物的形式输出水体,从而加大水体氮、磷、有机物的输出量,有减缓水体富营养化、净化饮水水质的作用;同时鱼类的摄食、消化、排泄等新陈代谢活动可加速水中氮、磷等物质循环,使藻类繁衍,如果大量放养草鱼还会导致水草资源破坏、生态失衡,对饮水卫生、安全不利;网箱养鱼投入饲料,直接增加了水源有机污染。围网养殖对局部水域生态平衡有破坏作用,放养密度过大,投入     

三峡水库和长江中下游通江湖泊(洞庭湖和鄱阳湖)草鱼、鲢的孵化日期及早期生长特征

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.     

我国大、中草型浅水型湖泊渔业综合开发技术进展

长江中下游湖大多属浅水草型湖泊,长期以来渔业利用处于薄后状态,1986－1990年国家在江苏鬲湖,湖北保定湖和安徽花园湖等地组织了大,中型浅水草型的湖泊的综合开发技术,包括水大面鱼病害控制,围养区层鱼捕捞技术,水体农业模式在内的科技攻关,本文以这五年取得的成果为主,概述了我国大,中型浅水草型湖泊渔业综合开发技术方面的进展。     

伊乐藻-草鱼圈养复合生态系统中水生生物的变化和影响

从细菌、浮游植物、浮游动物、底栖动物和有机碎屑等几个方面分析了养鱼对伊乐藻种植区(以下简称为有草区)和无草区水域环境的影响。结果表明:两个区域存在着显著的差异性。有草区由于生长着茂密的水生植被,对环境压迫的缓冲能力增强,水生生物的群落结构较为稳定,物种多样性指数高于无草区,有机物的沉降速率也大大低于无草区。与此相比,无草区对环境压迫的缓冲能力较差,水体浮游植物数量增加,富营养化加剧。通过本项实验可以看出,人工种植伊乐藻对养鱼区水质有着明显地控制作用,是发展生态渔业的一条有效途径。     

Zur Frage der Karpfenintensivbewirtschaftung von Seen und Eutrophierung

Normally, carp rearing at medium densities is connected with the promotion of daphnia and filtration effects up to “clear-water states”. Therefore and because of the reduction of submerged plants and of the periphyton this form of carp rearing should be possible in eutrophic shallow lakes also at a slight nutrient introduction without any considerable eutrophication. Due to a deterioration of the light climate by re-suspension of the sediment even reductions of the primary production are possible. In the case of the Galenbeck lake a drastic reduction of submerged macrophytes occurred in connection with an increased development of plankton, only general estimations being available of the shares of macrophytes and phytoplankton in the overall production. The phytoplankton increase is are perhaps caused by the absence of filtrating zooplankton due to an insufficient reduction of the indigenous fish stocks. In the Galenbeck lake the structural changes of the ecosystem were due both to the high degree of re-suspension of the very mobile lime sediment and the absence of hard bottom areas, which made the total reduction of the macroflora possible.     

Diversity of phytophilous macroinvertebrates in polycultures of semi-intensively managed fishponds

Both the diversity and abundance of water column phytophilous macroinvertebrates (PMI) were related to the fish stocking density, physico-chemical parameters in the water and semi-quantity of littoral aquatic macrophytes (AM). PMI were sampled in ponds with two types of polyculture 0+ or 2+/3+ common carp (Cyprinus carpio). The carp stock was combined with predatory fish pike (Esox lucius) or catfish (Silurus glanis) and herbivorous fish grass carp (Ctenopharyngodon idella) and/or silver carp (Hypophthalmichthys molitrix) in semi-intensively managed fishponds. Both the diversity of PMI community and abundance of most of the PMI trophic groups were negatively correlated with water depth and grass carp stocking density. Moreover diversity of PMI community was higher inside the beds of AM than in edge sites connected with open water. Neither polyculture with low stocking density of common carp 2+/3+ nor polyculture of common carp 0+ in the semi-intensively managed fishponds had a significant influence on the diversity of the PMI community. The abundance of PMI taxonomic groups was influenced by: (1) semi-quantity of reed sweet-grass (Glyceria maxima), (2) concentration of dissolved oxygen, (3) water depth, (4) common carp age 0+ or 2+/3+ and (5) quantity of fertilizer. Most of the PMI families were found in very shallow sites which were protected from fish, although environmental conditions there were more unfavourable, especially low oxygen concentration. The relationship between Glyceria maxima and PMI families seems to be related to its semi-terrestrial habitat (low water depth), growth dynamics and/or presence of aerenchyma. Supplemental food for fish increased the abundances of all of the PMI trophic groups.     

Variability of a cyprinid lake ecosystem with special emphasis on the native fish fauna under intensive fisheries management including common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix)

The lake investigated (Lake Heiliger See near the town of Angermünde, North-East Germany) is small (10.2 ha) but deep (z_max = 12 m, ? = 6.5 m). During summer the thermocline is at a depth of 4-5 m, and the hypolimnion is filled with H₂S already by mid-June, making 60-75% of the bottom area inaccessible to fish. The native fish fauna is dominated by planktivorous roach (Rutilus rutilus). A test stocking of silver carp (Hypophthalmichthys molitrix) together with an unplanned and erroneous stocking of common carp (Cyprinus carpio), coupled with an incorrectly calculated strong stocking of eel (Anguilla anguilla), which assumed that the total lake area yielded fish food organisms, brought about a strong depression of the food biomass available to native fish. Both silver carp and common carp showed a pattern of behaviour which only partly agreed with results obtained in experimental ponds prior to lake stocking. At least for 10 years there was a very low zooplankton biomass (mostly below 1 mg/l fresh weight) caused by silver carp and a strongly reduced benthos biomass (frequently below 1 g/m² fresh weight) caused by common carp and eel on H₂S-free bottom areas. Despite this extreme situation, which lasted for 20 years and is rarely found in lakes elsewhere, it was not possible to demonstrate negative effects on the native fish fauna comprising 16 species. Also the dominance pattern seems uninfluenced in the long run. A strong decline of the catchable roach stock was observed for some years, but the stock reappeared soon in comparable quantity. During the time of roach stock depression the individual growth of roach (and common carp) was particularly low. Nevertheless, roach succeeded in reproduction during this time in spite of the reduced zooplankton and detritus concentrations. Fry numbers per year ranged from 500-15 000 individuals/ha. The pike perch (Stizostedion lucioperca) was perhaps the most endangered species of all those living at small population numbers in the lake, since its fry is confined to the limnion where competition from silver carp and adult roach and perhaps predation by roach is highest. However the pike perch stock remained unchanged at the low level of 1950, the time prior of carp and eel stocking. All other rare species of Lake Heiliger See spawn in the littoral zone where fry survival conditions were less impacted. In summary, we present more evidence that the fish fauna of cyprinid lakes is more robust than in salmonid lakes. The regulation capacity of fish communities of eutrophic lakes seems to be able to offset even severe direct and indirect influences of fisheries management.