Seasonal habitat use by brook trout,Salvelinus fontinalis (Mitchill), in a second-order stream

Abstract Seasonal habitat use by over-yearling and under-yearling brook trout, Salvelinus fontinalis (Mitchill), was examined in a second-order stream in north-central Pennsylvania, USA. The habitat occupied by brook trout and available habitat were determined in a 0.5-km stream reach during the spring, summer and autumn of 1989 and the spring and summer of 1990. Cover, depth, substrate and velocity were quantified from over 2000 observations of individual brook trout. Habitat used by under-yearling brook trout was more uniform between seasons and years than that used by over-yearling brook trout. Over-yearling brook trout occupied areas with more cover and greater depth than did under-yearling brook trout, suggesting ontogenetic shifts in these variables. Differences for velocity and substrate were not as great as those for cover and depth. The selection of areas with low water velocities governed trout habitat use in spring, whereas cover and depth were the most important habitat variables in summer and autumn. Principal component analysis showed that available habitat and trout habitat centroids diverged most in spring, indicating that habitat selection by brook trout may be greatest at this time.     

Beyond catchment considerations in the conservation of lotic biodiversity

• 1. The history of river conservation has largely focused on preservation of the physical and structural properties of lotic ecosystems in an attempt to ensure safe and potable water supplies for human consumption. Such strategies are increasingly being implemented at the catchment or basin scale.
• 2. Although these reflect positive developments in the conceptualization of conservation issues pertaining to lotic systems and provide the logical economic, sociological and/or political units for management, we question whether they represent the appropriate scale for the protection of lotic biodiversity and biological processes. We argue that this requires considerations that extend beyond the protection of physical habitat to ensure protection of population processes.
• 3. Although many species can be successfully conserved using the catchment as the basic management unit, many others cannot. We review evidence from genetic studies of aquatic populations to examine movement in relation to catchments, recognizing that organisms with poor dispersal characteristics during their life cycles exhibit a high degree of genetic structure, whilst organisms with robust dispersal characteristics typically exhibit a homogeneous genetic structure.
• 4. Species with poor dispersal characteristics are more easily conserved at the catchment level, whereas those with high dispersal characteristics can only be safely conserved at bio‐regional supra‐catchment levels.
• 5. Modern technological advances aimed at redistributing water from areas with perceived surpluses to those with perceived deficits (inter‐basin water transfers), demonstrated to transfer organisms between historically isolated catchments, pose a potential threat to the conservation of biodiversity by mixing genetically distinct populations and hence altering evolutionary processes and pathways.
• 6. If our arguments hold, then it appears that conservation authorities need to reappraise the current dominant paradigm of the catchment as the basic unit for conservation and management, and incorporate broader, strategic landscape planning in water resource management.

Copyright © 2003 John Wiley & Sons, Ltd.     

Seasonal variations of chemical constituents in the muscle and viscera of small abalone fed different diets

SUMMARY: The seasonal changes in levels of chemical constituents in the muscle and viscera of small abalone Haliotis diversicolor fed gracilar and an artificial diet were investigated. Muscle yields were higher in winter and spring. In October specimens, total adenosine 5'-triphosphate (ATP)-related compounds (ARC), total free amino acids (FAA), and glycogen in both muscle and viscera decreased markedly. The artificial diet fed to small abalone had much higher glycogen in the muscle than those fed on gracilar, and showed a great seasonal change. Total amounts of ARC in the muscles were higher through March to July, while those in the viscera were maximal in January. Taurine, arginine, glycine, glutamic acid, and alanine were the major FAA in both tissues, accounting for 81–94% of the total FAA. Total amounts of FAA in the muscles were higher in the samples collected from winter and early spring than in other seasons. Glycine, glutamic acid, and adenosine monophosphate might be the most important taste components related to the palatability of small abalone. Their total amounts in the muscles of the two specimens were considerably high in December to March. This finding suggested that small abalone produced in winter and early spring might be more palatable.     

小型水库养鱼技术开发试验

对１０３座小型水库养高产技术进行了开发试验，１９９１年试验１０８５７亩，总产鱼１９０９．８Ｔ，平均亩产１７５．９ｋｇ每亩勇利３３５．４元，１ｋｇ盈利１．９１元；投入产出比１：２．０８。专家鉴定认为，本试验的面积产量均达到国内先进水平。     

不同光照强度西瓜光合速率日变化的研究

在温室条件下,以吊蔓栽培的小西瓜桔宝为材料,在其果实生长盛期对植株进行不同光照强度处理(自然光和50％自然光),并对其功能叶的净光合速率(Pn),空气温度和叶温、光合有效辐射(PAR)、蒸腾速率(E)、气孔导度( Cond)、胞间CO2浓度(Ci)、水分利用率(WUE)测定.结果表明:50％自然光下,西瓜叶片会出现略微...     

丘陵半干旱区小流域土地资源定量化评价研究

该文选择丘陵半干旱区国家水土流失重点治理区的辽宁朝阳市北四家小流域作为典型试验区，遵循发生学和主导因素原则，应用层次分析和聚类分析方法，通过划分小流域土地类型、确定土地评价指标体系、建立土地评价层次分析模型、构造判断矩阵、层次排序和一致性检验，将该流域土地资源划分为6个等级，并对各等级土地进行了适宜性评价，提出了其生态环境恢复重建和开发利用的方向。为我国丘陵半干旱区土地资源定量化评价和高效开发利用提供科学依据。     

坚持综合治理 发展小流域经济

坚持综合治理发展小流域经济王殿宝（北京市昌平县黑山寨乡水管站，１０２２１３）黑山寨小流域位于北京市昌平北部山区，面积４８ｋｍ２，有８个自然村，１６００户，５９００口人，３１００个劳动力，耕地只有２４６ｈｍ２。经济作物以林果为主，是闻名的板栗之乡。由于...     

珠海正坑小流域土壤与氮、磷养分流失估算

土壤及土壤养分流失是农业非点源污染的主要形式。选择珠江三角洲地区典型小流域——正坑小流域为研究区,在GIS技术支持下,建立流域数字高程模型并获取下垫面相关参数,采用通用土壤流失方程、固态污染物负荷方程,进行小流域农业非点源污染负荷估算与分析。结果表明,正坑小流域年土壤流失量为455061.60kg,旱坡地和果园两类土地利用景观类型具有相对较高的侵蚀模数;土壤N、P养分流失年负荷量分别为6335.32,1150.35kg,不同土地利用类型对非点源污染负荷的贡献率不同,水田中氮、磷流失对非点源污染负荷有重要影响。     

鲁中南山区小流域雨水资源化潜力的定量评价研究

为了探讨我国北方土石山区小流域雨水资源潜力及其水资源供需态势，为高效开发利用流域雨水资源和大规模开展生态环境建设工程提供理论依据。以代表该地区典型区域的鲁中南山区小流域为研究区域，在确定了小流域雨水资源理论潜力和现实潜力计算方法的基础上，对典型小流域雨水资源潜力及水资源供需平衡进行了定量分析。结果表明：该地区小流域总需水量中生态需水的比重最大，占总需水量的68．11％，农业生产需水量其次，占31．37％，人畜生活需水量最少，仅为0．52％。以小流域降水资源作为水资源的评估基础，当降雨设计频率分别为50％，75％和95％时，典型小流域的需水量占可供水量比重分别达到63．1％．75．2％和101．7％，研究区域典型小流域基本上都处于用水高度紧张状态，同时，提出了该地区未来小流域水资源开发利用的方向。     

不同下垫面降雨产流与旱地小麦集水补灌的产量及水分利用效率研究

在山西洪洞建立了农膜、公路、农田小路、农田下垫面产流场,对不同下垫面的自然降雨产流及早地小麦集水补灌的产量和水分利用效率进行了研究。结果表明：在观测的27次降雨中。不同下垫面的产流量存在较大差异,农膜、公路、农田小路和农田下垫面的产流系数分别为81．4％,73．6％,41．6％,2．7％。旱地小麦集水补灌研究表明：早地型品种应作为集水补灌早地小麦的主干品种;补灌量愈大产量愈高。拔节期补灌优于扬花期;同一补灌量集中补灌优于分次补灌;不同播期密度在集水补灌条件下其产量和水分利用效率存在差异。该项研究为开展集水工程及集水补灌提供了理论和技术依据。