Density,production, and survival of walleye (Sander vitreus) eggs in the Muskegon River,Michigan

Walleye (Sander vitreus) is an important sport fish in the Great Lakes that is experiencing low reproductive success after severe population declines starting in the late 1940s. In the Muskegon River, Michigan, natural reproduction of walleyes remains low and is largely supplemented by stocking. To determine factors influencing walleye reproductive success in the Muskegon River, we estimated walleye egg survival using insitu egg incubators covered with nitex screening (2003–2004) and estimated density and survival of fertilized eggs caught on furnace filter traps across different substrate types (2005–2006). We compared physical habitat suitability for walleye eggs under high and low flow scenarios. Density of walleye eggs was highest in regions of gravel/cobble substrates. Egg survival was higher in egg incubators (24–49.5%) than on furnace filter traps (2.0%), suggesting predation is an important source of walleye egg mortality in the Muskegon River. Cold water temperatures that extended developmental stage durations may also be an important source of egg mortality. The dynamic habitat suitability model predicted low suitability for eggs due to poor temperature and velocity conditions. Despite low egg survival rates, 40 million to 1 billion eggs were estimated to hatch. The low natural reproduction of walleyes in the Muskegon River is likely due to a combination of low walleye egg survival and failure of walleye larvae to reach their nursery grounds in Muskegon Lake.     

Spawning by walleye (Sander vitreus) and white sucker (Catostomus commersoni) in the Detroit River: Implications for spawning habitat enhancement

Few active fish spawning grounds have been found in channels connecting the Great Lakes. Here, we describe one near Belle Isle in the Detroit River, part of the channel connecting lakes Huron and Erie. There, in 2005, we collected 1,573 fish eggs, cultured them, and identified the hatched larvae as walleye (Sander vitreus) and white sucker (Catostomus commersoni). Walleye spawning peaked during the week of April 12–19; white sucker spawning peaked on May 10. Average areal rate of egg deposition by walleye and white sucker at this spawning ground in 2005 was 346 and 25 eggs/m², respectively. Our environmental measurements showed that bottom substrates on this spawning ground were largely sand, not optimal for fish reproduction. We hypothesize that reproduction of these fish at this spawning ground could be enhanced by adding rock and gravel substrates for protection of deposited fish eggs and suggest that reproduction by walleye in the Detroit River may add resilience to production of walleye in western Lake Erie.     

做好水库移民工作,促进金沙江下游水电开发

针对金沙江下游河段梯级电站地处云南、四川两省界河的地域特点、资源环境与社会条件,从跨省界河电站资源开发体制、梯级调度和建设管理基地布局、界河电站建设期税费征收、界河移民工作基本做法、移民管理信息系统建设以及"先移民,后工程"等方面对溪洛渡和向家坝两电站移民工作进行了初步总结,指出水电开发必须和当地经济社会发展与移民安稳致富紧密结合,构建水库移民、地方发展和电站建设互利共赢的长效机制。     

云龙河三级水电站碾压混凝土施工技术综述

碾压混凝土的初凝时间控制、温度控制、施工工艺是决定碾压混凝土坝质量好坏的关键,云龙河三级水电站在坝体碾压混凝土施工中,着重从这3个方面入手,在充分利用现有的先进碾压混凝土施工技术和工艺的基础上,大胆采用新技术,保证了施工质量和工期。     

基于IED模型的淮河蓄滞洪区运用对区域经济发展影响分析

为解决淮河蓄滞洪区经济发展严重滞后的问题,首先确定资本和制度是影响区域经济发展的核心因素,然后引入淮河蓄滞洪区运用的自然特性和社会特性,并通过构建IED模型综合分析了淮河蓄滞洪区运用对区内经济发展的影响。最后得出蓄滞洪区运用不仅会对蓄滞洪区造成直接损失,还会造成区内居民无法得到补偿的间接损失。研究表明:正是这些间接损失导致当地生产能力的下降。     

上海苏州河市区段防汛墙的加固改造

苏州河市区段两岸的防汛墙建设年代久远,建设标准低,存在巨大的安全隐患,迫切需要对现有防汛墙进行加固改造。在分析水文、地质和防汛墙现状的基础上提出加固改造方案,分别采取拆除新建型、墙前加固型、墙后加固型和骑跨式加固型等型式,根据地形选取不同的断面,结合苏州河沿线景观规划,以保证防汛安全为基础,兼顾生态环境和亲水平台建设,形成沿河公共开放空间。     

坚持依法行政原则 提高采砂监管水平

长江河道采砂管理工作具有重要性、长期性、艰巨性、复杂性、敏感性和高风险性等六大特征,采砂管理工作是水行政主管部门最难做、最富有挑战性的工作之一。相关主管部门必须始终坚持依法行政,始终坚持依法监管。结合新一轮机构改革后长江流域河道采砂管理的职能定位,就流域有关采砂管理的法律问题进行探讨,阐明坚持依法行政、依法监管原则对长江流域河道采砂管理工作的极端重要性。     

黄河下游二级悬河段河势及漫滩模型分析

结合实体模型试验,在洪量和沙量不变的情况下,对概化处理后不同量级洪水条件下黄河下游二级悬河段的水沙过程进行了研究。结果表明:随着洪峰流量加大,进入滩区的水量也随之增大,其漫滩范围和落淤厚度有逐步增大的趋势,但漫滩洪水基本流路无大的变化;漫滩洪水的水流交换模式包括在三角形滩区内完成的淤滩刷槽交换模式和水流漫滩后通过较长距离条形滩区落淤后回归主槽的交换模式。     

Delayed influence of dam storage and discharge on the determination of seasonal proliferations of Microcystis aeruginosa and Stephanodiscus hantzschii in a regulated river system of the lower Nakdong River (South Korea)

This study presents the relationship between the dam hydrology and phytoplankton proliferations in a regulated river system in East Asia. A long-term ecological study reveals that multi-purpose dam regulation on river flow in the Nakdong River (South Korea) affects proliferating patterns of phytoplankton, especially during summer (June-August) and winter (December-next February) as Microcystis aeruginosa and Stephanodiscus hantzschii, respectively, dominate each season by over 80%. Eutrophication was observed in the lower Nakdong River (South Korea) (mean+/-standard deviation: nitrate-N, 2.8+/-0.9 mg L(-1); phosphate-P, 40.3+/-31.3 microg L(-1); chlorophyll a, 45.2+/-84.9 microg L(-1); n=449), and the limnological characteristics responded to climatic variations such as monsoon and summer typhoons. The river basin experiences concentrated rainfall during the rainy season (June-September, over ca. 60% of total annual rainfall). Correlation and cross-correlation for time-delayed relationship revealed the hydrological environments (i.e., quantity of dam storage and discharge) had significantly negative relationship with the population dynamics of the two bloom-forming species for up to the next 2 years. S. hantzschii had clearer relationship with dam storage and discharge, which might be due to the seasonality exhibited by the species. The results support the necessity of "smart flow control" which may enable destruction of bloom formation by the two species with an adequate pulse of discharge generated by upstream dams in the far-east Asian river systems. This would increase the efficiency of water resource management system.     

黄河兰州段湿地景观水体净化处理及循环再生利用研究

黄河流域仅短期内抑制污染物,无法彻底分解污染物,导致水体净化和循环再利用效果差,提出黄河兰州段湿地景观水体净化处理及循环再生利用方法。通过种植旱伞草与鸢尾等植物,添加65%炉渣、25%砖块、10%砾石的填料,布设湿地景观,净化处理水体;利用厌氧池与缺氧池等一系列装置分解废水污染物,完成水体循环再生利用。试验表明,布设黄河兰州段湿地景观,有效净化处理水体内的化学需氧量、总磷、硝态氮,夏季指标的去除率高于冬季;布设黄河湿地景观,有效净化处理水体内的氨氮,冬季氨氮去除率高于夏季。水力负荷对化学需氧量、总磷的净化处理效果影响小;水力负荷越小,硝态氮的净化效果越佳;当水力负荷超过10 m3/（m2〖KG-*2〗·〖KG-*3〗d）时,氨氮的净化效果越佳。