The influence of diel period on fish assemblage in the unstructured littoral of reservoirs

Abstract Diel changes in littoral fish assemblage were studied in four reservoirs in the Czech Republic (Central Europe). The sampling was performed by beach seining in an unstructured littoral zone. Perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), bream, Abramis brama (L.), carp, Cyprinus carpio L., ruffe, Gymnocephalus cernua (L.), pikeperch, Sander lucioperca (L.), eel, Anguilla anguilla (L.) and A. brama × R. rutilus hybrids exhibited higher densities at night. Only bleak, Alburnus alburnus (L.) exhibited higher densities during the day. The number of species was higher in night hauls, and mean body size of roach and bleak was also higher at night. Diel changes in fish densities resulted in the change in species composition between day and night. The study has implication for the sampling design to assess littoral fish assemblages using beach seine netting and recommends night sampling for a representative assessment or sampling during both diel periods for a robust assessment.     

马肠道微生物组成及影响因素的研究进展

马肠道微生物群对其营养消化及维持机体健康具有重要作用,肠道不同部位的微生物具有不同功能,易受到各种因素的影响。马肠道正常微生物群结构遭到破坏,可导致肠道微生物失衡和机体功能紊乱,进而引起多种疾病。介绍了马肠道不同部位的微生物群结构组成特征,阐述了影响马肠道微生物群变化的各类因素,以期为改善马肠道营养健康、开发马健康监测和疾病预防工具提供科学依据,也为马肠道微生物研究提供新的视角。     

黄河三角洲不同土地利用类型土壤微观结构特征

黄河三角洲不同土地利用类型盐碱土微观结构的研究,对认识该地区盐碱土的工程性质和对滨海盐碱地治理具有重要意义。该研究结合粒度分析(particle size distribution,PSD)、X射线衍射(X-ray diffraction,XRD)、压汞(mercury intrusion porosimetry,MIP)和扫描电镜(scanning electron microscopy,SEM)方法,对3种不同土地利用类型盐碱土的微观结构进行定量分析,旨在揭示其微观特性,为黄河三角洲盐碱地治理提供微观理论依据。结果表明:不同土地利用类型下的土壤黏粒含量表现大小依次为农田、滩地、草地,而土壤孔隙度大小依次为草地、滩地、农田;农田、草地与滩地盐碱土矿物成分中,石英、方解石和钠长石等原生矿物占绝对优势,仅含少量黏土矿物,且农田黏土矿物含量远大于草地与滩地;草地与滩地盐碱土孔隙特征类似,两者在0.1≤孔隙直径<10μm范围内小孔隙与微孔隙占有绝对优势,而农田盐碱土以孔隙直径在<2μm范围内的微孔隙与超微孔隙为主。农田盐碱土由致密片状、扁平状结构与微裂隙构成,骨架颗粒间由黏土矿物胶结;草地盐碱土由紧密镶嵌的块状颗粒和架空孔隙构成,骨架颗粒间无胶结;滩地盐碱土由紧密堆积的粒状颗粒和粒间孔隙构成,骨架颗粒间无胶结。研究成果可提高对黄河三角洲不同土地利用类型盐碱土微观结构的认识,为滨海盐碱地的治理、利用和开发提供了微观尺度上的依据。     

不同叶面肥对狐臭柴叶片生物量和主要生化指标的影响

以三年生狐臭柴为实验材料,设置自然光和遮光两种光照条件,用三种叶面肥进行喷施,分析不同肥料对狐臭柴叶片生物量和主要生化指标的影响。结果表明:喷施氮肥能显著提高狐臭柴叶片生物量,自然光及遮光下分别增加37.30%和15.02%,但果胶的积累减少,分别降低19.78%和17.35%;磷肥能显著提升叶片果胶的含量,分别增加158.08%和239.96%,但叶片生物量显著低于对照,分别降低55.83%和47.40%;复合肥对叶片生物量无明显影响,果胶含量轻微降低。各肥料均使可溶性糖含量降低,且在遮光条件下使叶片内可溶性蛋白含量增加,自然光下使可溶性蛋白含量降低。     

乳山近海渔业资源种类组成及变化

根据2013—2015年乳山近海拖网渔船的渔捞日志,分析了乳山近海的单位捕捞努力量渔获量、渔获种类组成及生物多样性等特征。结果表明:(1)乳山近海渔获物共有36种,隶属于19目28科33属。其中鱼类有26种,虾蟹类4种,头足类4种,水母类1种,贝类1种。(2)2013—2015年全年优势种差异明显。其中,蓝点马鲛3年均为优势种,鳀鱼是2014年和2015年优势种,网纹狮子鱼为2013年和2015年的优势种。(3)乳山近海渔获物主要集中在休渔期前后的4—5月、9—11月,渔业生产存在明显的春汛和秋汛。2013—2015年乳山近海单位捕捞努力量渔获量逐年增加,但与历史单位捕捞努力量渔获量相比还是存在明显下降;多样性指数和均匀度指数变化趋势一致,多样性指数和丰富度指数较高值出现在秋季;春汛和秋汛期间,渔业资源种属组成及群落结构相似性较高。     

Impact of sampling and storage technique,and duration of storage,on the composition of fresh grass when analysed using near‐infrared reflectance spectroscopy

The objective of this study was to examine the effect of sampling technique (pluck or cut), storage duration (immediate analysis, 24‐h or 48‐h), storage temperature (ambient or chilled) and storage conditions (air present, air excluded or breathable) on the composition of fresh grass sampled from a sward managed to simulate grazing. Treatments were repeated across four sampling dates, with grass samples stored in grip seal bags prior to analysis using near‐infrared reflectance spectroscopy. Grass sampled by ‘pluck’ had a higher crude protein and ME content, and a lower acid detergent fibre (ADF) content, compared to that sampled by ‘cut’. Grass stored for 48 h had a lower water soluble carbohydrate (WSC) and ME content and a higher ADF content than for immediate analysis. Samples stored for 24 h did not differ from immediate analysis. Grass stored at ambient temperature had a lower WSC and ME content compared to immediate analysis. Grass stored under ‘breathable’ conditions had a lower ME content and higher ADF content than immediate analysis or samples stored with air present or air excluded. It is recommended that grass for analysis should be sampled by cutting, stored chilled (4°C) in a sealed bag to minimize exposure to oxygen and analysed within 24 h of harvest.     

Exploring tropical fisheries through fishers’ perceptions: Fishing down the food web in the Tonlé Sap,Cambodia

Tropical fisheries are among the most productive fisheries in the world, often providing the primary source of protein for the local population. Despite their importance, data on these systems are relatively limited, thus hampering management and policy development. Here, the implications of increasing fishing pressure are explored by critically evaluating the perceptions of the fishers who rely on these ecosystems to survive. A total of 169 fishers in 26 different fish‐dependent communities in the Tonlé Sap Lake, Cambodia, were surveyed to understand their perceptions of the impact that fishing has had on the ecosystem. The Tonlé Sap is one of the largest, yet poorest studied, freshwater fisheries in the world. Consistent with “fishing down the food web” theory of fisheries, survey data revealed that although fishers observed the total size of fish catch remaining consistent over recent years there has been a drastic decline in the size of individual fish, as well as a reduction in the diversity of species caught. These perceptions are examined with reference to food web theories that explore how fishing pressure leads to ecosystem change, including the more recent “indiscriminate fisheries” theory.     

杨木预水解过程中化学组分的降解行为及P因子调控作用

预水解具有环境友好性,符合生物炼制的理念。前期关于预水解的研究多集中于半纤维素的降解、分离和利用,而有关预水解过程中木质素降解的系统研究鲜有报道。以杨木为原料,在130~210℃条件下保温30~120 min进行预水解,结合P因子研究得率、葡聚糖、木聚糖、酸不溶木质素和酸溶木质素的降解率,揭示P因子对木质素降解行为的调控作用,探讨各化学组分在预水解过程中的相互作用。研究表明,预水解过程中木质素发生了一定程度的碎片化。随温度升高和时间延长,酸不溶木质素降解率均逐渐升高;当温度为190和210℃时,随时间延长,酸溶木质素降解率先升高后降低。试验证明,P因子对杨木木质素的降解具有调控作用。随着P因子增加,酸不溶木质素降解率呈指数上升,且分为快速降解(P因子<1500)和缓慢降解(P因子>1500)两个阶段;酸溶木质素降解率先上升后下降,在P因子为1926时达到最大值45.9%。此外,预水解过程中碳水化合物和木质素的降解具有相互作用关系。碳水化合物的降解为木质素的溶出打开了物理通道,同时木质素的重新吸附阻碍了其进一步降解。     

豆粕对乌鳢肠道菌群组成及微生物氨基酸代谢酶活性的影响

为研究豆粕替代鱼粉对乌鳢生长、肠道菌群组成和微生物相关氨基酸代谢酶活性的影响,分别用豆粕替代0、25%、50%和75%的鱼粉配制4组等氮等能的饲料饲喂初始体质量为(8.65±0.25)g的幼鱼(分别命名为G1、G2、G3和G4组),养殖实验在室内纤维玻璃钢桶中进行,实验周期为21 d。结果显示,各组间幼鱼成活率无显著性差异;G4组乌鳢幼鱼的生长性能显著低于G1和G2组,而G3组幼鱼生长性能与其余3组差异不显著。厚壁菌门在G1和G2组乌鳢肠道中的比例显著高于G3组,且在G4组中的比例最低;变形菌门在G1和G2组中的比例显著低于G3和G4组;G4组中乳球菌属、杆菌属、假单胞菌属、链球菌属、芽孢杆菌属和不动杆菌属的比例显著低于其余3组。另外,G4组幼鱼肠道微生物谷丙转氨酶、腺苷脱氨酶活性显著高于其余3组,而G1组乳酸脱氢酶的活性最高。研究表明,豆粕替代鱼粉除了对乌鳢幼鱼的生长产生影响外,也显著影响了肠道微生物组成及微生物相关氨基酸代谢酶的活性,本研究结果对于从微生态角度进一步理解豆粕在乌鳢配合饲料中的应用提供了理论依据和参考。     

云南怒江傈僳族自治州古树名木资源现状调查

对怒江傈僳族自治州人为活动区域古树名木资源现状进行调查。结果表明:共记录到古树名木496株,涉及36科54属76种,其中有8种国家重点保护野生植物,分别为澜沧黄杉、秃杉、南方红豆杉、云南榧树、千果榄仁、红椿、光叶珙桐和香果树;怒江州古树名木主要分布在乡村街道及远郊野外,占总数的98.8%,63.6%的古树生长在海拔1500~1999 m;古树名木的生长环境及长势总体较好,但保护力度相对薄弱,应采取相关措施加强保护和管理。