By-catch in the Saginaw Bay,Lake Huron commercial trap net fishery

This study provides species-specific catch and baseline mortality estimates of non-target species (by-catch) for the Saginaw Bay, Lake Huron commercial trap net fishery. By-catch can represent a significant mortality source that is often unknown. By-catch and by-catch mortality rates in the Saginaw Bay commercial trap net fishery, which primarily targets lake whitefish (Coregonus clupeaformis), yellow perch (Perca flavescens), and channel catfish (Ictalurus punctatus), are currently unknown. From May through August 2010, we observed onboard commercial trap net vessels and took species-specific counts of by-catch and estimated initial by-catch mortality (i.e., morbid or floating fish). The high levels of walleye (Sander vitreus) catch and mortality observed within inner Saginaw Bay have not been previously documented in the Laurentian Great Lakes. Walleye by-catch averaged 127.3 individuals per trap net lift and 42% of those caught were morbid. The levels of lake trout (Salvelinus namaycush) catch observed were within the range observed in previous studies, but mortality (percent) was higher than has been previously observed. Lake trout by-catch averaged 39.4 individuals per lift and 39.2% of those were morbid. Through the use of generalized linear models, this analysis also indicated factors that most influenced catch of non-target species including time of year and soak time (i.e., time interval between trap net lifts). Surface water temperature and trap net depth most influenced mortality. These results may inform fishers and fisheries managers and highlight the need for comprehensive by-catch monitoring throughout the Great Lakes.     

Spatial and temporal variability of inherent and apparent optical properties in western Lake Erie: Implications for water quality remote sensing

Lake Erie has experienced dramatic changes in water quality over the past several decades requiring extensive monitoring to assess effectiveness of adaptive management strategies. Remote sensing offers a unique potential to provide synoptic monitoring at daily time scales complementing in-situ sampling activities occurring in Lake Erie. Bio-optical remote sensing algorithms require knowledge about the inherent optical properties (IOPs) of the water for parameterization to produce robust water quality products. This study reports new IOP and apparent optical property (AOP) datasets for western Lake Erie that encapsulate the May–October period for 2015 and 2016 at weekly sampling intervals. Previously reported IOP and AOP observations have been temporally limited and have not assessed statistical differences between IOPs over spatial and temporal gradients. The objective of this study is to assess trends in IOPs over variable spatial and temporal scales. Large spatio-temporal variability in IOPs was observed between 2015 and 2016 likely due to the difference in the extent and duration of mid-summer cyanobacteria blooms. Differences in the seasonal trends of the specific phytoplankton absorption coefficient between 2015 and 2016 suggest differing algal assemblages between the years. Other IOP variables, including chromophoric, dissolved organic matter (CDOM) and beam attenuation spectral slopes, suggest variability is influenced by river discharge and sediment re-suspension. The datasets presented in this study show how these IOPs and AOPs change over a season and between years, and are useful in advancing the applicability and robustness of remote sensing methods to retrieve water quality information in western Lake Erie.     

A mesocosm investigation of the effects of quagga mussels (Dreissena rostriformis bugensis) on Lake Michigan zooplankton assemblages

Dreissenid mussels are known to disrupt the base of the food web by filter feeding on phytoplankton; however, they may also directly ingest zooplankton thereby complicating their effects on plankton communities. The objective of this study was to quantify the effects of quagga mussel feeding on the composition and size structure of Lake Michigan zooplankton assemblages. Two mesocosm (six 946 L tanks) experiments were conducted in summer 2013, using quagga mussels and zooplankton collected near Beaver Island, MI, to examine the response of zooplankton communities to the presence and absence of mussels (experiment 1) and varying mussel density (experiment 2). Mesocosms were sampled daily and zooplankton taxa were enumerated and sized using microscopy and FlowCAM® imaging. In experiment 1, the presence of quagga mussels had a rapid negative effect on veliger and copepod nauplii abundance, and a delayed negative effect on rotifer abundance. In experiment 2, mussel density had a negative effect on veliger, nauplii, and copepodite abundance within 24 h. Multivariate analyses revealed a change in zooplankton community composition with increasing mussel density. Ten zooplankton taxa decreased in abundance and frequency as quagga mussel density increased: except for the rotifer Trichocerca sp., treatments with higher mussel densities (i.e., 1327, 3585, and 5389 mussels/m²) had the greatest negative effect on small-bodied zooplankton (≤ 128 μm). This study confirms results from small-scale (≤ 1 L) experiments and demonstrates that quagga mussels can alter zooplankton communities at mesoscales (~ 1000 L), possibly through a combination of direct consumption and resource depletion.     

A lakewide survey of Asian clam (Corbicula fluminea) distribution at warmwater discharges in Lake Michigan

The Asian clam Corbicula fluminea is among the most prolific aquatic invaders in the world; but in colder mid-latitude areas, like the Laurentian Great Lakes, their population expansion has likely been limited by poor overwinter survival. In these areas, Asian clams are typically found in thermal refugia like warmwater discharges from industrial facilities. We sought to identify the current extent of Asian clam populations in Lake Michigan and waters immediately adjacent to it, specifically at locations most likely to harbor overwintering populations – industrial warmwater discharges. During April–May 2017, we surveyed 17 locations around Lake Michigan. Evidence of Asian clam populations was found at four sites, though live specimens (n?=?3) were only found at the Indiana Harbor Ship Canal in East Chicago, IN. Shells or fragments of shells were found at Green Bay, WI, Waukegan, IL, and Port Sheldon, MI. Our findings indicate that although Asian clams are present in Lake Michigan, they are relatively rare, and remain isolated to a few small pockets of over-wintering habitat.     

长江三峡工程对鄱阳湖生态环境的影响研究

三峡水利枢纽是一项规模宏大的系统工程,它的调度运行对整个长江流域的生态环境都将带来一系列复杂的影响。本文通过分析三峡工程的调度运行方式,研究其对鄱阳湖流域的防洪、冲淤、候鸟保护区、草洲、鱼类资源、血吸虫、水环境质量等方面所可能造成的影响。     

艾比湖流域生态环境保护措施的探讨

就艾比湖流域生态环境保护的对策提出一些建议：（1）建立艾比湖自然保护区和相应的管理机构；（2）建设河岸林；（3）严禁地下水超采；（4）发展饲草基地置换天然草场；（5）规划好调水工程等。     

江西省水权制度建设与探讨

江西省在水权制度建设中,重点开展了抚河流域水权分配试点研究,明确了工作思路的重点,提出了抚河流域水量分配方案。通过对抚河流域水权分配试点的研究,对水权理论有了进一步的认识,同时水量分配方案所采用的技术路线,为我国水资源相对较丰富流域或地区的水量分配方案编制提供了借鉴。     

南流江流域水环境问题及对策研究

在分析南流江流域水资源量、水质监测、污水排放等情况的基础上,针对流域水环境存在问题,提出了改善南流江流域水环境对策措施:调整产业结构,合理工业布局;加快污水处理厂建设,实现达标排放;实行总量控制,实现水环境良性循环;实施综合治理,改善水环境;完善监测网络,提高监测能力;优化水资源配置方式,改善水环境质量。     

松辽流域工业用水定额研究

从松辽流域视角出发，对辽宁、吉林、黑龙江、内蒙古四省（自治区）的工业产品定额进行分析，确定了工业产品的推荐用水定额；在分析基准年工业行业用水水平的基础上，采用不同方法对各水平年的需水定额进行了预测，给出了工业用水定额指标体系。     

松辽流域第三产业与建筑业用水定额拟定

用水定额是水权初始分配的重要基础，第三产业和建筑业用水定额是用水定额指标体系的组成部分。根据松辽流域的实际情况，拟订了松辽流域第三产业和建筑业用水定额，并做了校验，对用水定额、社会经济发展指标、用水量三者之间的关系进行了分析。