三峡水库和长江中下游通江湖泊(洞庭湖和鄱阳湖)草鱼、鲢的孵化日期及早期生长特征

三峡水库以及上游江段形成的河—库生态系统与长江中下游洞庭湖和鄱阳湖的江湖生态系统都是四大家鱼的重要栖息地,有相似性也有差异.2017年7—8月在三峡水库、洞庭湖和鄱阳湖利用地笼、虾笼、高网和迷魂阵采集草鱼和鲢幼鱼样本,观测耳石日轮,分析三峡水库和通江湖泊草鱼和鲢幼鱼的繁殖时间和早期生长特征及差异,探讨相应的保护措施.结果显示,三峡水库、洞庭湖和鄱阳湖采集草鱼幼鱼的孵化日期分别为4月24日—5月25日、5月21日—6月26日和5月4日—5月28日;鲢幼鱼的孵化日期分别为4月10日—6月12日、5月25日—6月19日和5月9日—6月12日.三峡水库、洞庭湖和鄱阳湖草鱼样本的体长增长率分别为1.04、1.84和1.64 mm/d,微耳石的沉积率分别为3.41、5.41和4.77μm/d;鲢幼鱼的体长增长率分别为1.10、2.87和1.96 mm/d,微耳石沉积率分别为2.96、7.17和4.57μm/d.洞庭湖草鱼和鲢的体长增长率和耳石沉积率均显著大于三峡水库;鄱阳湖鲢的体长增长率和耳石沉积率均显著大于三峡水库,而草鱼的体长增长率和耳石沉积率则与三峡水库没有显著差异.结果表明,三峡水库蓄水后长江中游干流草鱼和鲢的繁殖时间明显滞后;洞庭湖和鄱阳湖的草鱼和鲢幼鱼生长更快.目前,长江全面禁渔正在逐步实施,预期将对恢复鱼类资源起到重要的作用.除了全面禁渔之外,还建议保护和修复鱼类栖息地;减少江湖阻隔,灌江纳苗;增殖放流亲鱼;开展生态调度,促进鱼类繁殖.     

赣江发现溯河洄游型刀鲚(Coilia nasus)

基于鱼类江海洄游与否的电子探针耳石锶和钙微化学判别手段,对2020年5月采于赣江炉子窑江段的21尾刀鲚的生态表型进行了生活史重建的探索.研究发现,16尾为典型的溯河洄游型刀鲚,其占总刀鲚标本数量的比例达76%,远高于迄今鄱阳湖及其通湖水系所报道的相关比率.赣江中应该存在洄游型刀鲚的产卵场.这些首次确证了赣江中溯河洄游型刀鲚的存在,并体现出了在长江生态大保护及2019年2月1日业已开始的相关禁渔等国策下,赣江水域洄游型刀鲚资源量和栖息地有恢复向好的趋势.宜尽快开展赣江下游相关类群分布区和产卵场等及水利工程、河道挖沙等潜在威胁因素影响的全面调查,以便有效保护该水域的刀鲚资源及其关键栖息地.     

太湖常见鱼类生态学特点和增殖措施探讨

对太湖55种常见鱼类的生态学特点和种群动态等作了较全面的综合分析, 认为:鱼类的生态学特点和环境因子（包括人为因子）的综合作用是造成目前太湖在鱼类组成、种群数量上均以小型鱼类占绝对优势, 大、中型经济鱼类种群数量下降、结构低龄化的主要原因。因此, 太湖增值措施应包括:限制刀鲚发展、扶持翘嘴红鲌、鳜等名贵凶猛鱼类、加强人工放流、重点保护草上和水底部产卵鱼类、提高起捕规格等。     

太湖流域河流鱼类群落的时空分布

确定河流鱼类群落的时空分布格局及其形成机制是开展鱼类物种多样性保护与管理的科学基础.基于2013年10月和2014年5月共2次对太湖流域57个河道样点的调查数据,初步研究太湖流域河流鱼类群落结构及其多样性的季节动态和空间分布特点.共采集鱼类5051尾,计46种,其中鲤科鱼类26种,占全部物种数的57%.10月份的鱼类多样性显著高于5月份,且2个季度的鱼类群落结构存在显著性差异.5个主要水系间的鱼类多样性差异显著,总体上,沿江水系和洮滆水系鱼类多样性较低,黄浦江水系居中,而南河水系和苕溪水系较高;鱼类群落结构也随水系而显著变化,主要表现为黄浦江水系与洮滆、苕溪和沿江水系呈显著差异.在2个一级生态分区之间,鱼类多样性无显著差异但群落结构显著不同,主要因、鲫、似鳊等优势种及宽鳍鱲、尖头鱥、中华青鳉、食蚊鱼等偶见种的空间分布差异所引起;在4个二级生态分区之间,鱼类多样性和群落结构均存在显著的空间变化.     

On effects of trawling, benthos and sampling design

The evidence for the wider effects of fishing on the marine ecosystem demands that we incorporate these considerations into our management of human activities. The consequences of the direct physical disturbance of the seabed caused by towed bottom-fishing gear have been studied extensively with over 100 manipulations reported in the peer-reviewed literature. The outcome of these studies varies according to the gear used and the habitat in which it was deployed. This variability in the response of different benthic systems concurs with established theoretical models of the response of community metrics to disturbance. Despite this powerful evidence, a recent FAO report wrongly concludes that the variability in the reported responses to fishing disturbance mean that no firm conclusion as to the effects of fishing disturbance can be made. This thesis is further supported (incorrectly) by the supposition that current benthic sampling methodologies are inadequate to demonstrate the effects of fishing disturbance on benthic systems. The present article addresses these two erroneous conclusions which may confuse non-experts and in particular policy-makers.     

Results from a sixteen year study on the effects of oiling from the Exxon Valdez on adult pink salmon returns

For sixteen years following the 1989 Exxon Valdez oil spill adult returns of pink salmon in Prince William Sound, Alaska were monitored to assess spill effects on survival. No evidence of spill effects was detected for either intertidal or whole-stream spawning fish. From 1989 through 2004 mean densities for oiled and reference streams tracked each other, illustrating similar responses of oiled and reference stream adult populations to naturally changing oceanographic and climactic conditions. Hatchery fish strayed into the study streams, but similar incursions occurred in oiled and reference streams, and their presence was compensated for to eliminate their influence on determining the success of the returning natural populations. These results, showing no detectable effects of oiling on pink salmon spawning populations, are supported by published field studies on pink salmon incubation success in oiled streams.     

11-year cycle of spawning time and growth of the whitefish (Coregonus lavaretus) of Lake Constance

Over 90 years the beginning of spawning time of the whitefishCoregonus lavaretus of Lake Constance fluctuated in a wide range. A cycle of about 11 years is observed. Correlations of spawning time with sunspot activity (R), temperature, and age of spawners are found. Growth of the fishes in the first year of life correlates positively with R and year-class strength; growth in the second year correlates negatively with year-class strength and standing stock. It is assumed that the later the growing season ends the later the spawning season sets in.     

产卵迁徙对金沙江黑水河下游鱼类群聚结构变动的影响

鱼类作为河流生物的重要组成部分,其在干支流之间的迁徙或移动不仅是常见的,而且通常与鱼类的繁殖活动相联系.金沙江下游支流作为金沙江下游河流网络的重要组成部分,分布有较为丰富的集合生境以及较高的鱼类物种多样性.研究鱼类在金沙江下游干支流的产卵迁徙对支流鱼类群聚结构变动的影响以及支流生境维持对区域鱼类种群维系的意义,对金沙江下游干支流鱼类的保护具有重要的意义.本文拟选择黑水河下游江段作为典型研究区域,通过2014年在该区域的逐月渔获物调查,采用聚类分析、基于距离的线性模型以及基于距离的冗余分析等多种多元分析方法,确定黑水河下游群聚结构的逐月变动是否严重依赖于鱼类在干支流之间的产卵迁徙以及黑水河下游自然生境的维持对区域鱼类种群的维系是否具有重要的意义.结果表明:黑水河下游鱼类群聚结构在金沙江雨季和旱季显著分离的同时,表征这种分离的8种指示种的性成熟个体丰度也在雨季和旱季间发生不同程度的变动.7种指示种鱼类性成熟个体丰度的变动能够解释黑水河下游鱼类群聚结构变动77.20%的变异,其中齐口裂腹鱼、大鳞副泥鳅和犁头鳅性成熟个体丰度的变动是影响黑水河下游鱼类群聚结构变动的3个最显著的因素,7种指示种鱼类在干支流的产卵迁徙对黑水河下游鱼类群聚结构的变动造成了明显的影响.研究表明:在金沙江干支流严重水电开发背景下,维持黑水河现有的自然生境面积对区域鱼类种群的维持具有重要意义.为实行上述目标,建议在白鹤滩水电站蓄水运行后,拆除黑水河的部分小型水坝,并采取其他河流再自然化措施以维持黑水河现有的自然生境面积.     

三峡大坝运行前后西洞庭湖鱼类群落结构特征变化

鱼类是湿地生态系统中重要的组成部分,鱼类的群落结构动态直接反映湿地生境及外部驱动力的变化.三峡大坝运行后,长江中游江湖水文情势发生了变化,西洞庭湖地处洞庭湖西部,是受此变化影响最为直接的区域之一.为监测西洞庭湖鱼类群落结构变化特征,分析其变化原因,于2002年9月-2003年8月和2012年7月-2014年1月,在西洞庭湖进行了两次鱼类群落调查.共鉴定到鱼类7目17科91种,其中鲤形目最多,为58种,占总种数的63.7%.两次调查结果显示,三峡大坝运行后西洞庭湖鱼类物种数由85种下降到66种,Shannon-Wiener多样性指数和Pielou均匀度指数分别由5.00和1.11下降为4.14和1.00,鱼类个体小型化趋势明显.两次调查物种数和个体数量最多的类群均为底层、定居性、杂食性鱼类,且其比例有增加的趋势,而肉食性鱼类、中上层鱼类、半洄游性鱼类和产粘性卵、沉性卵鱼类个体数量占比均有减小的趋势,其中中上层鱼类变化有显著性差异.三峡大坝运行后10年间,西洞庭湖鱼类多样性呈现下降趋势.研究表明,西洞庭湖鱼类生境丧失、捕捞胁迫,加剧了一些特定类群的生存压力,并反映于鱼类群落结构的变化.     

Impacts of recreational motorboats on fishes: A review

A considerable amount of research has been conducted on the impacts of recreational boating activities on fishes but little or no synthesis of the information has been undertaken. This review shows that motor boats impact on the biology and ecology of fishes but the effects vary according to the species and even particular size classes. Direct hits on fishes by propellers are an obvious impact but this aspect has been poorly documented. Alterations in the wave climate and water turbidity may also influence fishes and their habitats, especially submerged and emergent plant beds. Sound generated by boat motors can also influence the communication and behaviour of certain species. Pollution arising from fuel spillages, exhaust emissions and antifouling paints all have detrimental effects on fishes. Finally, the use of recreational boats as vectors of aquatic invasive organisms is very real and has created major problems to the ecology of aquatic systems.     

悬浮泥沙水体对穗花狐尾藻(Myriophyllum spicatum L．)光合荧光特性的影响

对1997-2005年长江口亲蟹汛期渔获规格和捕捞量进行了研究,并对资源量和最大持续产量进行了估算.亲蟹平均壳长、壳宽和体重分别为61 mm、66 mm和142 g,雌雄个体比例为1:2.16;同期亲蟹年均捕捞量为2.03 t,最大持续产量参考值为1.06 t.研究期内亲蟹个体规格差异过大,捕捞量变动剧烈且时间分布有前移趋势,捕捞量相关因子的年间变动没有显著规律.此外,插网作业方式应予以禁止或限制,九段沙附近水域的捕捞强度也应得到有效控制.     

Derelict fishing nets in Puget Sound and the Northwest Straits: Patterns and threats to marine fauna

Derelict fishing gear remains in the marine environment for years, entangling, and killing marine organisms worldwide. Since 2002, hundreds of derelict nets containing over 32,000 marine animals have been recovered from Washington’s inland waters. Analysis of 870 gillnets found many were derelict for years; most were recovered from northern Puget Sound and high-relief rocky habitats and were relatively small, of recent construction, in good condition, stretched open, and in relatively shallow water. Marine organisms documented in recovered gillnets included 31,278 invertebrates (76 species), 1036 fishes (22 species), 514 birds (16 species), and 23 mammals (4 species); 56% of invertebrates, 93% of fish, and 100% of birds and mammals were dead when recovered. For all taxa, mortality was generally associated with gillnet effectiveness (total area, age and condition, and suspension in the water). Mortality from derelict fishing gear is underestimated at recovery and may be important for species of economic and conservation concern.     

The role of vegetation patterns in structuring runoff and sediment fluxes in drylands

The dynamics of vegetation‐driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps. At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients. At the stand scale within‐storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small‐grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them. Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd.     

Die heutigen sympatrischen Felchenpopulationen (Coregonus spp.) des Thuner-und Bielersees und ihre Morphologie

During the past 25 years the effects of eutrophication in the oligo-to mesotrophic Lake Thun and the eutrophic Lake Biel have changed the morphology and biology of theCoregonus spp., as well as the composition of the stock. Statistical procedures and immunodiffusion revealed the existence of threeCoregonus populations in Lake Thun: 5% Kropfer, 28% ‘Albock’ and 67% Brienzlig (local names). Their gillrakers range between 20 and 32, 25 and 40, and 29 and 46, respectively (mean: 22, 31, 40). In Lake Biel two populations were distinguished: 16% Palée and 84% Bondelle with 22–35 and 30–40 gillrakers (mean: 30, 34). Changes of the spawning grounds and periods most probably have led to a bastardization of two species (Schwebalbock and Bodenalbock) to the present ‘Albock’ in Lake Thun. Overlapping values of all 20 morphological characters of the populations studies render the identification of forms difficult. Only gillrakers and a few more characters show significant statistical differences between populations. The determination ofCoregonus spp. of Lake Thun and Lake Biel thus often needs additional data on growth, feed, maturation, spawning ground and/or period.      

Does the timing of the spawning migration change for the southern component of the Northeast Atlantic Mackerel (Scomber scombrus,L. 1758)? An approximation using fishery analyses

Part of the Northeast Atlantic mackerel population migrates towards the southern spawning area (Cantábrian Sea) at the end of winter. In this seasonal handline fishery targeting mackerel, the most important in the study area that targets this species, the timing of the peak of catches has shifted forward (later) in recent years. This paper presents results pointing to the likelihood that this shift is due to a change in the timing of the spawning migration to the southern area of the Northeast Atlantic mackerel population. Three types of fleet have been identified within this fishery, and in all of them there is a forward shift in time in effort exerted. Moreover, a new model has been defined for the standardization of catch per unit effort (CPUE). The fishing season appears to have shifted forward by 29 days between 2000 and 2006. Nevertheless, changes have been detected neither in the exploitation pattern nor in the duration of the fishing season during the period studied. A shift on this scale has important consequences for the management of the resource, the fleets that exploit it and the resource assessment survey designs that will have to be adapted to this new scenario.     

Patterns of Seagrass and Sediment Nutrient Distribution Suggest Anthropogenic Enrichment in Laamu Atoll, Republic of Maldives

Sampling of seagrass cover and sediment nutrients was undertaken in lagoonal habitats of Laamu Atoll (Republic of Maldives) adjacent to three traditional fishing villages (fishing the predominant economic activity for more than 30 yr), three other villages (not traditional landing sites), and four uninhabited islands to determine if chronic input of organic fishing waste from the traditional fishing villages could explain spatial distribution of seagrass cover. Results indicated significantly greater cover of seagrass at the traditional fishing village sites than the other two site groups. Analysis of dried sediments showed sediments at traditional fishing village sites were significantly enriched with phosphorus, though no significant difference in nitrogen was found between groups of sites. These results, together with studies showing that sediment nutrient pools can limit seagrass bed development, suggest that anthropogenic enrichment of lagoonal sediments by fishing waste over generational time scales may have caused substantial proliferation of seagrass beds.     

Fish in the littoral zone: ecology, threats and management

The importance of the littoral zone of lakes to a diversity of fish species has been appreciated for many centuries, although the complexity and heterogeneity of this habitat have resulted in a poorer understanding of local fish ecology compared with that achieved for typically much larger but simpler offshore habitats. Lake fish species may occupy the littoral zone permanently or visit it on diel, seasonal or ontogenetic timescales in response to a range of intrinsic and extrinsic factors. The purposes of such occupations include feeding, refuge from predation and, most importantly for many species, reproduction. The primary environmental threats to fish in the littoral zone arise from eutrophication, which may directly or indirectly alter feeding conditions through the loss of macrophytes, from increases or decreases in water level variations and from siltation rates, both of which may interfere with spawning or egg incubation, and from the introduction of alien species, many of which preferentially colonise the littoral zone where they may act as predators, competitors or environmental degraders. The management of these threats is best accomplished through general lake management measures such as the control of nutrient levels, but some actions specific to the littoral zone or its fish populations are also feasible. These include the replacement of lost or damaged spawning substrata, the active management of water levels at appropriate times of year, and, at least potentially, the deployment of artificial structures to provide appropriate physical habitat for adult fish.     

Multiscale structure of UXO site characterization: spatial estimation and uncertainty quantification

Unexploded ordnance (UXO) site characterization must consider both how the contamination is generated and how we observe that contamination. Within the generation and observation processes, dependence structures can be exploited at multiple scales. We describe a conceptual site characterization process, the dependence structures available at several scales, and consider their statistical estimation aspects. It is evident that most of the statistical methods that are needed to address the estimation problems are known but their application-specific implementation may not be available. We demonstrate estimation at one scale and propose a representation for site contamination intensity that takes full account of uncertainty, is flexible enough to answer regulatory requirements, and is a practical tool for managing detailed spatial site characterization and remediation. The representation is based on point process spatial estimation methods that require modern computational resources for practical application. These methods have provisions for including prior and covariate information.     

Meiofaunal community structure in Thermaikos Gulf: Response to intense trawling pressure

Among the most important impacts of trawling is the disturbance of the benthic environment as well as the mortality of the larger benthic organisms, which is caused by the passage of the fishing gear. Meiofauna, which are among the smallest benthic organisms, may be more resistant to disturbance by trawling since they are likely to be re-suspended rather than killed by trawls. Their short generation times allow populations to withstand elevated mortality. In this study, we determined the effect of trawling disturbance, season and sediment type on the structure of meiofaunal communities in a commercial fishing ground in Thermaikos Gulf, north Aegean Sea, Greece. The trawling season is limited to 8 months between October and May. A grid of five nearshore stations was chosen along a north–south productivity gradient and an additional offshore station was included as a reference point. Sediment chemistry and meiofaunal community structure were studied before the trawling season started, as well as 1 and 4 months after the initiation of the fishing period. Results showed that there were no short term (30 days) trawling impacts on meiofauna in terms of abundance and community structure but that there were recognizable effects on the community structure of nematodes and the abundance of polychaetes. In contrast, most meiofaunal taxa displayed significant seasonal variability, 4 months after the initiation of the fishing period; however, other closely related factors such as temperature, sediment particle size and primary productivity are more likely to be responsible for the observed patterns.     

Modeling of soil heterogeneity and its effects on seismic response of multi-support structures

This paper addresses the analytical evaluation of soil lateral heterogeneity effects,especially the random fluctuations of the soil layer's predominant frequency,on the spatial coherency of ground motion and the seismic response of multi-support structures.A coherency probabilistic model is proposed.In this model,the spatial variation of motion is attributed to wave passage effects,effects of loss of coherence in the bedrock motion and particularly site response effects(based on the assumption of vertically propagating shear-waves through a horizontal layer with random characteristics).The results indicate that soil lateral heterogeneity effects tend to cause diminution of the values of the total coherency function.This diminution is not limited to the vicinity of the mean resonant frequency of the layer,but reaches considerably high frequencies even for relatively low values of coefficient of variation(CV of 5 to 15%).Therefore,the trend of the total coherency function(exponential decay) can be influenced significantly by site effects.Finally,the proposed coherency model is applied for two different support seismic excitations.Study results indicate that the greater the soil heterogeneity,the larger are the dynamic displacements and shear forces in the columns of the oscillator(i.e.,support structure).Furthermore,these two components of the response are influenced differently by soil heterogeneity effects.