阳澄湖网围养殖区水体营养盐的时空变化与水质评价

2008年5月至2009年5月在阳澄湖中湖网围养殖区采集上、下层水样进行水质检测，并采用营养状态指数法对养殖区营养状况进行综合评价。结果显示，（1）养殖区营养盐的分布存在明显的时空变化，除了硝酸盐以外，所测指标均表现为养殖季节高于非养殖季节，高密度养殖区高于低密度养殖区，底层水高于表层水，说明高密度养殖造成氮磷的大量沉积。（2）高密度养殖区呈重度富营养状态，低密度养殖区也达到中度富营养。（3）2008年5月与2009年5月同期的水质监测数据显示，单季养殖的湖泊水质变化不明显。本研究表明，短期养殖对水质影响较小，但长期养殖则影响明显。网围养殖区富营养化日趋严重，目前已接近重度富营养状态，且磷污染较氮污染严重。     

湖泊小面积网围精养高产高效技术的研究

湖泊网围养鱼是近几年兴起的新型渔业生产方式。是改革传统湖泊渔业利用方式的一项突破。随着网围养鱼技术的推广应用,我国的湖泊渔业取得了长足的进步。但由于网围养鱼历史较短,各地生产经营水平不同,总的还存着单产水平低,群体增重倍数不高,经济效益不高的问题。如何提高湖泊网围养鱼的单产水平。提高经济效益,这是湖泊网围养鱼进一步推广应用中急需解决的课题。鉴于以上情况,我们在滆湖进行了湖泊网围养殖高产技术的研究,现将试验情况介绍如下。材料和方法试验条件:本研究以滆湖南部的官林围养场、丰义乡围养场为试验点,供试验用网围建在湖底平坦,远离航道处;平均水深1.5米,底质为粘土,流速一般为0.1米/秒;水质良好,溶解氧0.81—10.35毫克/升,PH值8.04～8.36。试验规模:本研究主要以30亩以下面积为     

沂蒙湖网围养殖青虾试验

沂蒙湖蓄水面积７００多公顷，平均水深１．６米，最大水深５．２米，常年水位稳定，有微流水，水质良好，水中溶氧充沛，无污染，天然饵料丰富。为了发展湖区经济，开发利用湖水水面，增加经济效益，２０００年我们承担了临沂市科委下达的网围养殖青虾项目，经过１年的实施，取得了显著的经济效益。１围拦和放养方法１．１网围设置方法网围设在沂蒙湖湖心岛东部，该水域环境安静、无污染，水位１～１．５米，有微流水，底部较为平坦且具有一定淤泥，适合养殖青虾。网围由聚乙烯材料制成，网目（２a）１厘米，网高２米，网围面积５０００米…     

以滆湖为例湖泊种植饲料水草的养鱼效果研究

本研究以典型的浅水草型湖泊滆湖为对象,通过对几种水草营养成份的分析,草食性鱼类对这几种水草摄食程度的比较,发现草鱼、团头鲂最喜食的水草为苦草、轮叶黑藻和菹草。为促进这些饲料水草的繁茂,在湖区进行了这三种水草不同方法的种植及合理利用技术的试验。根据所得结果,提出了苦草刈割间隔期以23天为宜;通过割草养鱼试验,提出了蓄草养鱼的配套技术措施,并对滆湖网围养鱼的发展提出建议。     

如何使湖泊网围养殖业良性发展

近年来，由于河蟹价格的攀高，湖泊网围养殖河蟹效益的提升，不少湖泊出现了生产单一、畸型发展的局面。加上不合理的操作方法及人为的酷渔滥捕，影响了湖泊渔业资源和湖区的生态平衡，严重破坏了湖泊渔业的可持续发展。 　　超密度网围养殖对湖泊渔业及环境影响： 　　1.超密度网围养殖造成湖区水草锐减，使湖区失去了净化水质的支柱 　　湖区水草不仅是鱼类饵料及水生动物栖息的场所，而且对湖区渔业及水环境的平衡起很大的调节作用。水生植物又能防浪消浪，减少湖区悬浮物，使湖水水质洁爽，增加水体透明度，有利于植物的光合作用，提高…     

湖泊网围鲢鳙鱼生态低碳养殖效益高

<正>鲢鳙鱼是我国传统四大家鱼中的两种,是典型的滤食性鱼类,根据鲢鳙鱼的生理和生态习性一般在养殖生产中都把其作为混养而非主养种类。江苏滆湖是苏南地区仅次于太湖的第二大淡水湖泊,随着周边经济的快速发展,滆湖近二十年来出现了严重的富营养化和生态破坏等环境问题。监测结果表明,滆湖的总氮、总磷含量较上世纪80年代增长了近10倍,富营养化已导致滆湖从草型湖泊转变为现在的藻型湖泊,水生植被大量消失。为探索一种改善滆湖生态环境和控制藻类过度繁殖的生态渔业模式来替代传统网围养     

EM原露在水产养殖上的应用试验

1998年以来,多次由江苏省无锡市农林局立项,应用EM原露进行了常规鱼和主养青虾养殖、滆湖网围河蟹养殖试验，现将情况介绍如下：一、EM原露在水质调控中的应用1.EM原露加红糖发酵制成活性液后使用在常规鱼池和青虾池养殖中,用量第一次泼洒至少为1毫升/米3,以后根据水质状况按亩     

滆湖1988年鱼产量通过部级验收

滆湖水产增养殖技术研究是国家“七五”重点攻关专题。这一研究任务于1986年下达后,有关科研人员经过3年努力工作,采取科研与开发、推广相结合的方式推动了滆湖渔业生产迅速发展,到1988年,全     

洪泽湖网围养蟹技术

洪泽湖网围养蟹是在洪泽湖浅滩水域用网布、竹箔为防逃设施,圈围一块水体投放蟹种进行集约化养殖的一项新的养殖技术。根据两年来对洪泽湖网围养蟹试验研究的结果,参照河蟹人工养殖的基础理论,将其主要技术简介如下:一网围选址与网围面积     

过水性湖泊网围河蟹鳜鱼混养技术

高邮湖位于淮河人江水道下游，总面积达到7．72万hm^2，属大型过水性湖泊，过水性特征显著。为了适应高邮湖水环境变化，提高水产养殖业的抗灾能力，探索过水性湖泊生态养殖模式，2007年至2008年试验网围河蟹、鳜鱼混养模式，这既可以充分利用水体空间和水体天然饲料生物资源，在不影响河蟹产量的前提下，每667m^2可增加10～20kg的鳜鱼产量。通过两年来对网围河蟹鳜鱼混养模式的调查，该模式具有养殖周期性短、     

基于底栖动物生物完整性的武汉市湖泊生态系统健康评价

大型底栖动物是生态系统健康评价最常用的生物类群。本文以武汉市浅水湖泊为研究区域,分析近20年（1998-2018）野外调查的104个湖次底栖动物数据,初步构建适合我国中部浅水湖泊底栖动物完整性评价的多参数指数MMI (Multimetric Index),包括36个群落结构性参数和35个功能性参数共71个生物参数,经筛选武汉湖泊MMI指数由总分类单元数、腹足类个体数%、功能趋异指数和穴居者%共4个核心指标组成。通过比值法将健康状态划分为5个等级：健康、亚健康、一般、差和极差。回归分析结果表明,MMI指数不仅与富营养化指标关系显著,能够反映湖泊营养状态的变化;而且能够显著区分城市湖泊与农村湖泊,城市湖泊的健康状况明显差于农村湖泊。基于MMI的健康评价结果表明,武汉市湖泊健康状况一般,其中34.6%湖泊健康状况亚健康以上,41.3%的湖泊健康状况处于一般水平,24.1%湖泊健康状况较差。本研究构建的包含功能性状参数的MMI完整性指数,可在湖泊健康评价中推广应用,也为湖泊修复和可持续发展提供了科学基础。     

长荡湖水生植被动态及其渔业效应的研究

本文根据1983年—1984年调查研究结果分析整理而成。文中论述了长荡湖现有水生植被的种类组成,群落结构,生态分布,沉水植物的生物量及其利用。经过分析比较,发现近30年来,长荡湖水生植被经历了旺盛—衰竭—恢复—旺盛的演替过程,揭示了引起植被变化的各种因素。随着水生植被的动态变化,长荡湖的鱼类种群结构,渔获对象及捕捞工具都相应发生了变化。植被的盛衰同浮游植物和浮游动物、底栖生物的消长丰歉有着密切的关系.本文最后指出了长荡湖水植被的演替趋势和潜在危机,强调了合理利用和定向改造水生植被的重要性,并对今后如何发展我国湖泊渔业提出了建议。     

Abundance and spatial distribution of the Mediterranean scallop,Pecten jacobaeus,in a marine lake

Pecten jacobaeus is an exploitable bivalve, whose populations have greatly declined in the main Mediterranean fisheries since the mid-1980s. A substantial population of the species was studied in the marine Lake Vouliagmeni (Korinthiakos Gulf, Greece). The population density and the spatial distribution of P. jacobaeus were estimated in the lake with line transect sampling by SCUBA diving, a method not previously used for scallop density estimations. Individuals of the first size class (small) were mainly restricted to shallow waters (4–8 m), while individuals of the second size class (large) were mainly restricted to deeper waters (>12 m). Possible reasons for this size-separation were: (1) the most appropriate settlement substrate for pediveligers was in shallow waters, (2) the strong summer thermocline in the lake may have induced the selection of the shallow and warm bottoms of the lake as settlement areas, (3) intraspecific competition between adults and pediveligers, and (4) the high fishing mortality of large individuals in shallow waters. On the hypothesis that successful recruitment of P. jacobaeus occurred mostly in the shallow areas of the lake, it was deduced that P. jacobaeus gradually migrated, as they grew, from the shallow settlement fields of the lake to the deeper areas. The density of large individuals was associated with depth and the degree of scatter (QDφ) of the granule size frequencies. Higher densities of large individuals were found deeper and in poorly sorted sediments (QDφ > 1.0). The size of large individuals was positively correlated with depth. The size of P. jacobaeus population in Lake Vouliagmeni was estimated.     

Growth performance of fingerlings in pen culture

Abstract. Studies were conducted on the growth performance and development of one-year-old fingerlings of seven species in lake pen culture. It was found that the body weight and length of the fingerlings increased evenly with each passing month. Based on the increase of length, these 7 species could be categorized into two groups; while based on body weight gain, they could be categorized into three groups. The growth Index of power functional relations concerning the weight and length ranged between 2·8 and 4·0, indicating that the two growths were in parallelism. It was considered that the condition factors should be calculated with b -value according to the differences of fish species and ages (month). The monthly average indexes of the length and weight increases of the seven species were calculated.     

The complementary role of lentic and lotic habitats for Arctic grayling in a complex stream‐lake network in Arctic Alaska

Lakes can be important to stream dwelling fishes, yet how individuals exploit habitat heterogeneity across complex stream‐lake networks is poorly understood. Furthermore, despite growing awareness that intermittent streams are widely used by fish, studies documenting the use of seasonally accessible lakes remain scarce. We studied Arctic grayling (Thymallus arcticus) in a small seasonally flowing (June–October) stream‐lake network in Alaska using PIT telemetry. Overall, 70% of fish visited two lakes, 8% used a single lake, and 22% used only stream reaches. We identified five distinct behavioural patterns that differed in dominant macrohabitat used (deep lake, shallow lake or stream reaches), entry day into the network and mobility. Some juvenile fish spent the entire summer in a shallow seasonally frozen lake (average 71 days), whereas others demonstrated prospecting behaviour and only entered the stream channel briefly in September. Another group included adult and juvenile fish that were highly mobile, moving up to 27 km while in the 3‐km stream‐lake network, and used stream reaches extensively (average 59 days). Lentic and lotic habitats served differing roles for individuals, some fish occupied stream reaches as summer foraging habitat, and other individuals used them as migration corridors to access lakes. Our study emphasises the importance of considering stream‐lake connectivity in stream fish assessments, even to shallow seasonally frozen habitats not widely recognised as important. Furthermore, we demonstrate that individuals may use temporary aquatic habitats in complex and changing ways across ontogeny that are not captured by typical classifications of fish movement behaviour.     

Habitat overlap of juvenile and adult lake trout of Great Bear Lake: Evidence for lack of a predation gradient?

A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush, are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT, Canada, occupied a variety of habitats and from shallow to deep depths (0–150 m), overlapping with adult lake trout. No evidence occurred for a length depth‐based segregation (e.g., ontogenetic shift). Genetic variation was also similar among juveniles in the different depth zones. However, isotopic niches and C:N ratios among juveniles showed some variability in niche widths and positions for individuals caught from the 51–150 m zone compared to juvenile individuals caught from 0–20 m and 21–50 m zones. The uniformly distributed adult lake trout in Great Bear Lake may evenly distribute predation pressure (including cannibalism) across shallow‐ and deep‐water habitats more than in other lakes. As a result, juveniles may respond to differences in foraging opportunities rather than predation risks. Juvenile lake trout did not appear to conform to the general pattern of juveniles seeking a deep‐water refuge to reduce predation risks. In contrast, juvenile lake trout of Great Bear Lake displayed broad resource use across all depths and habitats.     

Does habitat occupancy by lake trout and lake whitefish in large lakes match published thermal habitat envelopes?

Habitat occupancy patterns of lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) in two large Canadian Shield lakes were modelled based on detections of fish from repeated depth‐stratified surveys over several summers. Lake trout and lake whitefish consistently occupied sites outside traditional thermal envelopes and were not detected at some sites within these ranges. This included the metalimnion and shallow epilimnion for lake trout and lake whitefish in Lake Opeongo. Physical habitat covariates were not important in defining lake trout habitat in both lakes. Physical habitat as represented by the hardness/softness gradient based on acoustic substrate surveys was important for lake whitefish in Lake Opeongo but not in Smoke Lake. In addition, thermal envelopes for lake whitefish differed between the lakes possibly because of differences in substrate slope. The wash zone of lakes, where the thermocline contacts the substrate, appears to be a physical habitat feature for lake whitefish in some lakes. Lake whitefish also exhibited diurnal activity behaviour that was reflected through greater detection rates in the morning versus the afternoon. By accounting for imperfect detection, true estimated overall occupancy of lake trout and lake whitefish increased 0.15–0.30 over naïve occupancy. Thermal habitat envelopes for lake trout and lake whitefish are wider than previously thought. Lake trout occupied a consistent thermal habitat envelope while lake whitefish varied between lakes likely because of lake specific differences in basin morphology and wash zone.     

Detection efficiency and habitat use to inform inventory and monitoring efforts: juvenile coho salmon in the Knik River basin,Alaska

Imperfect detection associated with sampling gear presents challenges for wildlife inventory and monitoring efforts. We examined occupancy dynamics and habitat use of juvenile coho salmon, Oncorhynchus kisutch, in shallow lake environments over a summer and early fall season in the Knik River area of south central Alaska using models which control for and estimate sampling gear detection efficiency. In addition, we present statements for the probability that observed absences at a survey site or from a survey area (a collection of sites) are true absences given some amount of sampling effort and analysts' beliefs about site occupancy and sampling gear detection efficiency which can be used to guide inventory and monitoring efforts for juvenile salmon or other wildlife and plant species. Occupancy modelling results demonstrate that minnow traps were effective at sampling juvenile coho in shallow lake environments, with a mean probability of detection across the study period of 0.68 (i.e., probability of detecting the presence of juvenile coho given that they are present at a trap site; SE = 0.03). Juvenile coho salmon migrated into shallow water lakes in late summer and early fall, presumably to seek out overwinter habitat. N‐mixture modelling examination of habitat use demonstrated that once in shallow lake environments, juvenile coho were widely distributed across a range of microhabitats, with some evidence for preference for shallower depths and warmer water temperatures.     

Migration,homing and spatial ecology of common carp in interconnected lakes

The common carp, Cyprinus carpio, is a large, long-lived, fecund and mobile cyprinid, which evolved in complex inter-braided Ponto-Caspian rivers that experience both springtime flooding and freezing winters. Studies suggest adults often move to productive, shallow lakes and floodplains to spawn because they often lack egg predators and then return to deeper normoxic waters to overwinter. Whether these movements involve individuals consistently selecting, or homing to, the same spawning and refuge lakes as part of a strategy benefiting their reproductive success is unknown. To address this question, we examined the movements of 67 radio-tagged adult carp for 3 years in a watershed with 11 interconnected lakes. Carp were tagged and released into a centrally located, normoxic deep lake in spring and fall. Each spring over 95% of its adults left via a single stream and swam into one of 5 shallow lakes, with most individuals (84%) selecting the same lake(s) in which to spawn each year (median Bhattacharyya affinity coefficient of similarity of 0.82). Young were later found in those lakes without egg predators, which cannot survive winter anoxia. After spawning, carp spent summers moving between productive lakes in an individualistic fashion, presumably foraging, with most (89%) eventually returning to the same deep lake to overwinter (median Bhattacharyya affinity of 1.0). These movements appear to reveal a life-history tactic involving seasonal homing migration, first to a spawning location and later to winter refuges, that is well adapted to productive but highly heterogeneous and interconnected freshwater environments.