老江河底栖动物变化动态及渔业利用

１９９１－１９９４年对老江河底栖动物进行了连续４ａ的季节采样,共获底栖动物３２各,其中寡毛类８种,水生昆虫１０种,软体动物１２种,其他２种,底栖动物年的均密度变动于２９７－３７３个／ｍ＾２,年龄生物量变动于８３．６１２－１８．２１７ｇ／ｍ＾２。对底栖动物的季节变动,多样性指数变化进行了分析,并对底栖动物的渔产潜力进行了估算。     

Combined effects of best management practices on water quality in oxbow lakes from agricultural watersheds

Water quality conditions in three oxbow lakes were examined before and after best management practices (BMPs) implementation within the Mississippi Delta. Experimental design called for the development of structural and cultural treatments to reduce sediment and associated pollutants entering watershed oxbow lakes. Three watersheds were selected and developed with different levels of BMPs. Changes in lake water quality were used as measures of management success. Analyses of water quality data prior to the implementation of BMPs suggested the lakes were stressed and ecologically damaged due to excessive sediment inflow. Significant improvements in water quality were observed with the use of cultural and structural BMPs. Sediments decreased 34–59%, while Secchi visibility and chlorophyll generally increased. The most dramatic improvements in water quality occurred in the two watersheds that featured cultural practices and combinations of cultural and structural practices. Reducing suspended sediment concentrations in these oxbow lakes favored phytoplankton production resulting in increased chlorophyll concentrations and higher concentrations of dissolved oxygen. Cultural BMPs, more so than structural BMPs, play a vital role in improving lake water quality, and are needed in addition to structural measures to ensure improved water quality in oxbow lakes receiving agricultural runoff.     

Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Background, aims, and scope  Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods  Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the ¹³⁷Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results  Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. ¹³⁷Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre-1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends were most prominent for heavy metals and anthracene, less prominent for DDTs, and almost absent for PCBs and most PAHs. Discussion  Different temporal and spatial patterns for various contaminants make it possible to distinguish between anthropogenic point sources from local industry (anthracene, Cr, Cd), possible diffuse sources (most PAHs), and geological background (V, Co, Ni, and Mo). The observed recent trends in heavy metal and persistent organic pollutant contamination are generally consistent with data from other Central European rivers. The roughly balanced contamination levels in sediments from the lake and the adjacent river channel suggest that the oxbow lake deposits reflect immediate levels of the contamination bound to suspended particulate matter passing through the river. Conclusions  The investigated oxbow lake accumulated suspended sediment from Morava River, developing a thick sedimentary body. The sediments offer a good time framework to study historical contamination of the river on a decade time scale. Continuous contamination trends can be traced back to the early 1980s. The results show that stratigraphic analysis of cores has a good potential for identification of uninterrupted historical trends and unconformities, e.g., due to dredging. Recommendations and perspectives  Oxbow lakes may provide an alternative to floodplains and reservoir deposits when studying river contamination history. High sedimentation rates of up to 7.7 cm/year offer a very good stratigraphic resolution, making it possible to study contamination patterns on annual or even seasonal time scales. On the other hand, oxbow lakes may represent long-term contamination stores, which are unlikely to be redistributed by river erosion and, hence, may possess significant environmental risks for the farther future.     

长江天鹅洲故道鱼类群落结构特征及其年际变化

根据2010-2011年和2015-2016年对长江天鹅洲故道鱼类资源的调查,分析了长江天鹅洲故道鱼类种类组成、优势种和物种多样性的变化,着重了解长江江豚(Neophocaena asiaeorientalis asiaeorientalis)潜在饵料鱼资源-小型鱼类的情况。结果表明,2次调查共采集到鱼类51种,隶属于6目12科41属,其中2010-2011年采集鱼类50种,2015-2016年采集鱼类38种。小型鱼类共采集到32种,其中2010-2011年度为31种,2015-2016年度为22种,减少的种类主要为长江干流繁殖进入天鹅洲故道的种类。2015-2016年相比2010-2011年,小型鱼类优势种也发生了较大的改变,2010-2011年故道小型鱼类优势种5种,按优势度大小排序为:短颌鲚(Coilia brachygnathus)、贝氏歺又鱼(Hemiculter bleekeri)、鲫(Carassius auratus)、似鳊(Pseudobrama simoni)和银鮈(Squalidus argentatus);而2015-2016年优势种为4种,按优势度大小排序为:黄尾鲴(Xenocypris davidi)、歺又鱼(Hemiculter leucisculus)、短颌鲚和鲫,来自长江干流繁殖的小型鱼类资源有所减少。建议通过灌江纳苗引入似鳊、银鮈、贝氏歺又鱼等长江干流繁殖的小型鱼类,改善生境,为歺又鱼、鲫等湖泊定居鱼类提供良好的繁殖环境,以增加长江江豚饵料鱼类的资源量,满足其食物需求。     

长江天鹅洲故道银鮈年龄、生长和死亡率的研究

根据2011年3月至2012年1月在长江天鹅洲故道采集的银鮈(Squalidus argentatus)样本873尾,用鳞片为年龄鉴定和生长退算材料,研究银鮈的年龄、生长特性及死亡率.结果表明,雌雄群体均由1～6龄组成,雌鱼87.35％为1～3龄,雄鱼87.01％为1～3龄.雌雄鱼体长(L)和体重(W)关系表现为异速生长,雌鱼w=0.009L3.2285,雄鱼w=0.009L3.2254.以退算体长拟合von Bertalanffy方程,得到生长参数为:雌鱼L∞=17.1797cm,k=0.1820,t0=-1.2673和雄鱼L∞=11.5069cm,k=0.4074,to=-0.5764.雌雄鱼的自然死亡率分别为M=0.6048/a和M=1.1459/a,远高于一般鱼群自然死亡率(M=0.2～0.3/a);开发率分别为E=0.5711和E =0.4183.长江天鹅洲故道银鮈雌鱼处于过度开发的状态,应加强管理.     

长江天鹅洲故道鲢、鳙、草鱼和青鱼种群特征与数量变动的初步研究

本文报道兴建中的长江天鹅洲“四大家鱼”天然种质资源库中鲢、鳙、草鱼与青鱼的生长，死亡特性和资源数量变动规律。对这4种鱼生长参数值的比较分析表明，天鹅洲故道鲢、鳙、草鱼、青鱼基本维持了长江天然群体的优良生长特性，1991年度，故道渔获量为71.8万公斤，其中“四大家鱼”产量8，8万公斤，鲢、鳙、草鱼、青鱼的死亡率分别为0.66、0.77，0.86、0.86，。四大家鱼”的年资源补充量为16.7万尾，平均资源重量为7.28万公斤，目前该故道渔业所存在的主要问题是过度捕捞，为了发挥种质资源库的预期效应，建议将。四大家鱼。的开捕年龄定为3龄，严禁捕捞其当年幼鱼，捕捞强度控制在0.3～0.5间，以期故道鲢、鳙、草鱼、青鱼的持续产量保持在30万公斤左右，     

长江天鹅州故道鱼类群落种类多样性↑（*）

１９９３年２月至１９９４年１月,在长江开敞型的天鹅洲故道采集鱼类４９种,分属５目１３科,其鱼类群落由湖泊型鱼类和江河型鱼类组成。Ｓｈａｎｎｏｎ指数、Ｗｉｌｈｍ改进指数和Ｓｉｍｐｓｏｎ指数分别为３．７０、４．１９和０．８９;均度为０．６６。年总渔获量为３７４５３０．８ｋｇ,其中青鱼、草鱼、鲢及鳙共占１７．９７％。由于捕捞过度,天鹅洲故道鱼类群落表现为强烈的小型化、低值化趋势,年总渔获量的６６．１８％为小型、低值鱼类。     

长江天鹅洲故道鲢、鳙、草鱼和青鱼种群特征与数量变动的初步研究

本文报道兴建中的长江天鹅洲“四大家鱼”天然种质资源库中鲢、鳙、草鱼与青鱼的生长，死亡特性和资源数量变动规律。对这4种鱼生长参数值的比较分析表明，天鹅洲故道鲢、鳙、草鱼、青鱼基本维持了长江天然群体的优良生长特性，1991年度，故道渔获量为71.8万公斤，其中“四大家鱼”产量8，8万公斤，鲢、鳙、草鱼、青鱼的死亡率分别为0.66、0.77，0.86、0.86，。四大家鱼”的年资源补充量为16.7万尾，平均资源重量为7.28万公斤，目前该故道渔业所存在的主要问题是过度捕捞，为了发挥种质资源库的预期效应，建议将。四大家鱼。的开捕年龄定为3龄，严禁捕捞其当年幼鱼，捕捞强度控制在0.3～0.5间，以期故道鲢、鳙、草鱼、青鱼的持续产量保持在30万公斤左右，     

长江天鹅洲白鱀豚国家级自然保护区鱼类资源现状

了解湖北长江天鹅洲白鱀豚国家级保护区的鱼类资源现状,为豚类保护措施的制定提供参考,也为长江渔业资源的保护和管理提供依据。于2017-2019年在保护区水域进行了渔获物和渔业水声学调查。调查共采集到鱼类83种(亚种),结合历史资料,保护区共分布有鱼类154种(亚种),隶属于11目25科85属。历史资料中的71种在此次调查中未采集到,有7种为此次调查新增种类。长江干流和天鹅洲故道的优势种和鱼类密度均存在较大差别。在保护区长江干流江段,黄颡鱼(Tachysurus fulvidraco)和银鮈(Squalidus argentatus)为优势种,在天鹅洲故道,光泽黄颡鱼(Tachysurus nitidus)和贝氏歺又鱼(Hemiculter bleekeri)为优势种。长江干流和天鹅洲故道的鱼类资源平均密度分别为(0.40±0.38)和(0.94±0.81)尾/m~3。调查结果表明,保护区的鱼类资源仍处于衰退的进程中,需针对保护区不同水域采取不同的保护措施。     

长江天鹅洲故道“四大家鱼”种质资源天然生态库建库可行性研究

天鹅洲故道水面面积为１３．７－３０．０ｋｍ＾２。据１９９１－１９９４年的调查，该故道具有以下优良性状：（１）水质好，溶解氧为５．７－１０．５ｍｇ／ｍｌ，透明度为０．３－１．７５ｍ。（２）水生生物丰富，共有１６门，３０６种。（３）鱼类种类繁多，计有９目１８科７７种。（４）家鱼资源丰富，性状优良。每年７－８月约有近２０万尾鲢、鳙、草、青鱼苗种进入故道育肥，其渔获量在７万ｋｇ左右；生长参数的比较分析证明