Spatial distribution and abundance of small fishes in Xiaosihai Lake,a shallow lake along the Changjiang (Yangtze) River, China

Spatial distribution and abundance of small fishes were studied in autumn 2007 in the Xiaosihai Lake, a shallow lake along the middle reach of the Changjiang （Yangtze） River. Based on the plant cover, the lake was divided into three major habitats： Myriophyllum spicaturn habitat （MS habitat）, Trapa bispinosa habitat （TB habitat）, and non-vegetation habitat （NV habitat）. A modified pop-net was used for quantitative sampling of small fishes in the three habitats, and the Zippin＇s removal method was used for estimating densities of the small fishes. A total of 13 species belonging to 5 families were collected, with 11 species in MS habitat, 7 species in TB habitat, and 5 species in NV habitat. Habitat type had significant effect on the spatial distribution of small fishes. The Shannon-Wiener diversity index in the MS, TB and NV habitats were 1.28, 0.56 and 0.54, respectively. The total density and biomass of small fishes were significantly higher in the MS habitat （13.68 ind/m^2 and 4.44 g/m^2） than in the TB habitat （1.41 ind/m^2 and 0.54 g/m^2） and the NV habitat （1.08 ind/m^2 and 0.40 g/m^2）, and were not significantly different between the TB habitat and the NV habitat. Water depth had no significant effect on spatial distribution of the small fishes. It was suggested that vegetation type played an important role in habitat selectivity of small fishes, and the presence of submersed vegetation should be of significance in the conservation of small fish diversity.

Spatio-temporal variability of small fishes related with environmental factors in a typical domestic tap water lake, Eastern China

The knowledge of prey small ?sh stock, distribution and abundance is necessary to guide stocking of piscivorous ?sh for the biomanipulation in domestic tap water lakes. This study describes the current status of small ?sh community in Kuilei Lake(China), and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on submerged macrophyte cover and water depth, the lake was divided into ?ve major habitats:(1) macrophyte covered shallow habitat of water depth< 2.00 m,(2) uncovered or less-covered shallow habitat(2.00 m–3.50 m),(3) uncovered medium shallow habitat(3.50 m–5.00 m),(4) uncovered medium deep habitat(5.00 m–6.50 m) and(5) uncovered deep habitat(6.50 m–8.50 m). The abundance and composition of small ?sh were monitored by benthic fykenet sampling from April 2013 to January 2014. A total of 2881 individuals belonging to 5 families and 21 species were collected. Based on their abundance(accounted for 88.96% of the total) and occurrence(more than 33.33%), Acheilognathus chankaensis, Acheilognathus macropterus, Microphysogobio microstomus,Pseudorasbora parva and Rhinogobius giurinus were recognized as dominant small ?sh species. The results of correlation analysis identi?ed that species richness( Sr), Shannon-Wiener diversity index( H′)and Margalef′s richness index( D) were signi?cantly negatively correlated with water depth, but positively correlated with biomass of submerged macrophytes.Redundancy analysis(RDA) revealed that the spatial distributions of most small ?shes were negatively associated with water depth. The details of these ?ndings are bene?cial to understanding the adaptation of the small ?shes in degraded environments, and to developing suitable biomanipulation strategies for the management of ?sh resources and water quality in the lakes along the lower reach of the Changjiang(Yangtze) River basin.

Effect of Socio-Economic Variables on Fish Production of Small Farmers in Tocantins State, Brazil

Fish farming is a strategic activity for both the economy and food security of the Tocantins state. Nowadays, there are about eighty small fish farmers in the region of Divin6polis in Tocantins state. The technological level of fish farmers is low and it was found that only 30% of farmers could ever get to the point of selling fish. Therefore, the objective of this paper is to investigate which socioeconomic factors have influence on the fact of fish farmers in the region of Divin6polis and in Tocantins state reach a level of efficiency in production enough that the fish can be good for sale in the local market. To estimate this relation the logit model was chosen, with methodology based on the empirical model used in Musaba and Namukwambi. Following the production of fish farms in the Western of Tocantins state, the collect of the data, during 2012, were conduct with interviews of 30 fish farms, visiting them in their homes and applying a questionnaire. Through the use of econometric models of probability for limited dependent variables, it was found that factors such as participation in federal programs to transfer income, total area of water and production in ponds are key factors in determining the likelihood of producer to sell fish.

Characterization of refined fish oil from small fish in Mauritania

In this study,the effects of chemical refining on the physicochemical indices,environmental pollutants,lipid functional groups,relaxation characteristics,fatty acid profiles,and triglyceride(TG)molecular species in crude oil extracted from small fish in Mauritania were evaluated.The acid,peroxide,and iodine values of crude oil were identified as 5.52 mg KOH/g,1.73 meq/kg,and 200.78 g/100 g oil,respectively.After refining,these values were determined to be 0.29 mg KOH/g,0.76 meq/kg,and 210.80 g/100 g oil,respectively.The polychlorinated biphenyls and arsenic content of crude oil were identified as 32.30μg/kg and 1.00 mg/kg,respectively.After refining,these were not detected.The content of eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA)accounted for as much as 87.55%of the polyunsaturated fatty acids in the refined oil,indicating that high-quality fish oil is suitable as a food supplement.The correlation coefficient of the infrared spectra before and after refining was 0.968,and the relaxation time and peak shape data were almost similar before and after purification.Meanwhile,there were no significant differences(P≥0.05)in fatty acid profiles between the crude and refined oils,except for C16:0(P<0.01).Based on UPLC-Q E-MS/MS detection,137 TG molecules were identified in both crude and refined oils.Among the detected TG molecular species,64 contained EPA or DHA,which accounted for 46.83%and 46.00%of the total TG content in crude and refined oils,respectively.After refining,the content of the molecular species decreased by 31.95 mg/10 g,among which the three most variable molecular species were TG(16:0/18:1/22:6),(16:1/16:2/18:1),and(18:4/16:0/20:5),accounting for 29.26%of the decline of the molecular species.Overall,the refining process had little effect on the fatty acid profile and distribution of TG molecular species in fish oil.

Relationship Between the Spatiotemporal Distribution of Dominant Small Pelagic Fishes and Environmental Factors in Mauritanian Waters

The relationship between the spatiotemporal distribution of three dominant small pelagic fishes,including chub mackerel(Scomber japonicus),horse mackerel(Trachurus trecae)and round sardinella(Sardinella aurita),and the environmental factors in Mauritanian waters were analyzed by using 4 years of logbook data of commercial purse seine fisheries to improve the efficiency of fishery and management of sustainable exploitation.A Tweedie-generalized additive model(GAM)of 8-day average catches and the monthly geostatistical analysis of daily catches were used in this study to analyze the influence of environmental factors on catch per unit of effort(CPUEs)and to map the spatial distribution of three mixed dominant small pelagic fishes,respectively.A 10'×10' grid was used,and environmental factors were processed from remote sensing,including 8-day average sea surface temperature(SST),the nearest distance between SST fronts and CPUE position(Df),chlorophyll-a(Chl-a)concentration,salinity,and eddy kinetic energy.Results showed that 1)the distribution of three dominant small pelagic fishes might be related to the intensity of upwelling in Mauritanian waters;2)oceanic fronts might play a key role in the ecology of chub mackerel,horse mackerel,and round sardinella;3)Chl-a concentration might be associated with the feeding grounds of chub mackerel;4)the target species distribution appeared sensitive to gradient changes in the amount of salinity;5)three zones(northern,central,and southern)with variable abundances were delineated;and 6)a high concentration of the center of gravity in the central zone might be related to the strong upwelling of nutrient-rich waters.This study can provide new insights to enhance the fishery efficiency and sustainable exploitation management of purse seiners in certain area off Mauritania.

The Influence of Land Use and Fish Farming on the Contents of Ca²⁺, Mg²⁺, K⁺and Na⁺in Pond and Reservoir Ecosystems in an Agricultural Small Watershed, China

It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca2+, Mg2+, K+ and Na+) in small water bodies of pond and reservoir ecosystems at the watershed scale. In this study, the concentrations of Ca2+, Mg2+, K+ and Na+ in water bodies were measured for 103 ponds and reservoirs used as fish farming or surrounded by different agricultural land use types in the subtropical hilly watershed of Jinjing (105 km2), China. The two important environmental factors of fishing farming and agricultural land use influenced the spatial variation the contents of alkali metals. The ponds and reservoirs in residential area had significantly higher concentrations of Ca2+ and Na+ than those with other land use types, reflecting the influence of domestic wastewater. Compared with those of natural ponds with non-fish farming, no significant increase of alkali metal contents occurred in fish farming ponds, due to the regular cleaning of ponds by farmers. However, the effect of fish culture on alkali metal contents was still supported indirectly by the fact that the alkali metal contents significantly correlated with nitrate contents in fish farming ponds and but high related with that of DIP in natural ponds. The suitability assessment for irrigation on the pond water indicated that almost all of ponds were suitable for irrigation except some ponds surrounded by residential area and tea plantation. Generally, our results demonstrated that fish farming and agricultural land use affected the contents of alkali metals in ponds and reservoirs. The agricultural water irrigation would be with caution from the ponds with tea plantation and residential area in the subtropical hilly watershed.

习近平治国理政的传统智慧及其阐释逻辑——以“治大国若烹小鲜”为例

习近平法治思想从多方面展现大国治理的传统智慧,在方法论问题上,习近平特别提到老子的“治大国若烹小鲜”。从历史逻辑上讲,习近平古语新说,遵循逻辑与历史相统一的辩证法,为“治大国若烹小鲜”注入了更多的新时代内涵。从法理逻辑上讲,“治大国若烹小鲜”蕴含的传统智慧与全面依法治国、比例适度原则、权力监督制约等现代法治理念和宪法精神深度契合,从总体性、协同性和控制论等不同维度生动诠释了习近平的法治方法论。从实践逻辑上讲,“治大国若烹小鲜”的治国理念是宪法权衡思维的生动体现,对于在法治轨道上全面推进民主政治、市场经济、和谐社会、先进文化和生态文明等方面的建设具有重要的方法论意义。

不同装载条件下小型渔船参数横摇的非定常RANS CFD仿真

Fishing boats have unique features that make them prone to changing loading conditions.When the boat leaves the port,the empty fish tank gradually fills up during fishing operations which may result in parametric roll(PR).This dangerous phenomenon that can lead to capsizing.The present study aims to understand better the behaviour of parametric roll in fishing boats and its relation to changing loading conditions.The study considers the effects of displacement and the GM/KM ratio on parametric roll,as well as the longitudinal flare distribution at the waterline.Two assessments to detect the parametric roll occurrence in early stage were carried out by using the level 1 assessment of parametric roll based on the Second Generation of Intact Stability criteria(SGIS)from International maritime Organisation(IMO)and the Susceptibility criteria of Parametric roll from the American Bureau of Shipping(ABS).Then,the CFD method is used to predict the amplitude of the parametric roll phenomenon.The results provide important insights to fishing vessel operators on how to manage loading conditions to maintain stability and avoid hazardous situations.By following the guidelines outlined in this study,fishing boats can operate more safely and efficiently,reducing the risk of accidents and improving the overall sustainability of the fishing industry.

波浪作用下小尺度多船并排锚泊横摇运动试验研究

采用物理模型试验方法研究双船、三船和四船并排锚泊时各船的运动量,并与单船艏艉锚泊情况进行了对比,重点分析了横浪作用下各船的横摇运动规律,探究了波浪周期和并排锚泊船数对多船并排锚泊时横摇运动的影响。结果表明,多船并排锚泊时,横摇运动响应随着波浪周期的增大而逐渐减小。双船并排锚泊时,横摇运动响应同单船相比减少了40%~50%;三船和四船并排锚泊时,横摇运动响应同单船相比减少50%~60%,四船并排锚泊时横摇运动响应减小的幅度与三船并排时相比差别不大。

基于人工鱼群-遗传算法的多品种小批量零件数控加工工艺优化研究

基于多品种小批量零件加工成本高的问题,基于人工鱼群-遗传算法(AFSA-GA)构建了数控机床能耗模型,以实现零件加工能耗下降。首先,将数控机床功率划分为各工序功率模型,基于功率模型与工作时间关系得出机床运转能耗模型,结合产品表面粗糙度模型,对各工序能耗模型及整体粗糙度进行归一化处理,形成整体能耗模型;其次,以能耗及粗糙度为目标函数,建立AFSA-GA算法,通过对各工序能耗求解得出最适当的机床功率及其所对应的能耗和表面粗糙度;最后,针对所获得的最优功率,进行优化结果的验证,为五轴机床的实际加工提供解决方案。

气候变化对中国近海中上层小型鱼类影响的研究进展

近年来气候变化持续影响海洋环境,同时也影响着海洋鱼类的群落变化和生态系统的稳定。中上层小型鱼类对气候变化较为敏感,其在我国海洋渔业中逐渐占据重要地位。近年来,虽有大量的研究探究了气候变化对鱼类的影响,但是气候变化对中上层小型鱼类全面系统的研究相对较少。鉴于上述原因,本文根据国内外的相关研究成果,综述了由气候变化引起的海水表面温度、盐度、酸碱度、溶解氧含量、叶绿素a浓度、海平面上升以及海流和极端事件频发等海洋环境因子变化对海洋中上层小型鱼类的影响,这种影响主要体现在个体发育、栖息地、洄游模式、群落结构及其资源丰度等方面。气候变化下中上层小型鱼类的分布区通常向高纬度或深海区转移,从而导致群落结构改变,对渔业资源造成影响。本文通过探讨气候变化对海洋渔业的影响,旨在从中探寻应对气候变化的有效对策,从而为海洋渔业在气候变化的背景下实现可持续发展提供理论依据。

Status and historical changes in the fish community in Erhai Lake

Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data （1952-2010） describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis （CCA） plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake （a decrease from seven to two species）. In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.

菌解小分子鱼肽肥对毛竹鞭笋生长及竹林土壤生态的影响

毛竹林经营过程中为提高鞭笋产量而重施化肥造成竹林生态退化和竹笋品质降低,引进菌解小分子鱼肽肥,通过研究不同肥料配施方式对毛竹鞭笋产量及竹林土壤生态因子的影响,探明菌解小分子鱼肽肥对毛竹生理生态的作用机制。以相同经营现状的毛竹笋用林为研究对象,设置4个肥料配施处理(CK为750 kg·hm^(-2)复合肥、T1为375 kg·hm^(-2)复合肥、T2为“375 kg·hm^(-2)复合肥+150 kg·hm^(-2)菌解小分子鱼肽肥”、T3为“375 kg·hm^(-2)复合肥+300 kg·hm^(-2)菌解小分子鱼肽肥”)进行施肥,于鞭笋笋期统计鞭笋产量,测定土壤养分元素质量分数、土壤酶活性、叶片叶绿素以及叶片养分元素质量分数等指标,分析各指标在不同施肥处理之间的差异显著性和不同指标之间的相关性。结果表明:与750 kg·hm^(-2)复合肥处理相比,“375 kg·hm^(-2)复合肥+150 kg·hm^(-2)菌解小分子鱼肽肥”和“375 kg·hm^(-2)复合肥+300 kg·hm^(-2)菌解小分子鱼肽肥”处理时的鞭笋产量分别提高39.39%、29.09%。比较于750 kg·hm^(-2)复合肥处理和375 kg·hm^(-2)复合肥处理,“375 kg·hm^(-2)复合肥+150 kg·hm^(-2)菌解小分子鱼肽肥”处理显著提高了土壤p H以及有机碳、全氮、全钾、水解性氮、速效钾等土壤养分元素质量分数,显著提升了土壤脲酶、蔗糖酶、酸性磷酸酶活性,同时增加了叶片叶绿素以及碳、氮、钾等元素质量分数。相关性分析结果表明:鞭笋产量与土壤p H、有机碳、全氮、水解性氮、全钾、速效钾质量分数、蔗糖酶活性以及竹叶叶绿素、有机碳、氮、钾质量分数呈极显著正相关。菌解小分子鱼肽肥和复合肥合理配施可通过提高土壤肥力和土壤酶活性,促进毛竹养分元素吸收,从而提高鞭笋产量,减少化肥施用量。

基于改进YOLOv5的鱼群小目标检测优化算法

随着深度学习技术的发展,水下图像检测近年来受到广泛的关注,为了克服在复杂水下环境下传统小鱼群的误检、漏检和识别准确率低等问题,提出一种改进YOLOv5的目标检测方法(INV-YOLOv5)。该方法包括将YOLOv5m中的Focus模块替换为卷积模块,提高网络精度;在主干网络(Backbone)中添加多头自注意力机制,增大网络特征提取视野;最后,在网络中引入了内卷算子和加权的特征融合,降低网络的参数量,提高检测精度。在实验阶段,使用Labeled Fishes in the Wild数据集和WildFish数据集验证,该方法的平均精度(mAP)分别为81.7%和83.6%,与YOLOv5m网络相比分别提升了6%和14.5%,不仅拥有较高的识别率并且更加轻量化,而且模型大小与YOLOv5m网络相比减少了6 M(Mega)左右,验证了所提出的改进方法具有较好的效果。

“探究小鱼对光照强度的反应”实验教学设计与实施

“探究水蚤对光照强度的反应”实验在教学过程中存在较多弊端。用小鱼替代水蚤,自制亚克力水槽替代玻璃管,连接带有电池盒的LED冷光灯,探究鱼类对光照的行为,应用计算机软件准确计算和分析实验结果,提升了实验的安全性、便捷性和准确性。

基于模糊算法的非标鱼塘智能增氧机控制系统设计

针对目前我国非标小型鱼塘占比大,传统增氧机无法实现节能降耗、自适应调节等问题,研究设计一种基于模糊算法的增氧机智能控制方案。利用两级模糊控制动态调整变频器输入电压并对变频器固定的PID参数进行实时优化,通过智能控制系统驱动变频器调整增氧电机的转速,实现了对池塘各水层溶解氧浓度的精确调控。实验结果表明,该方案能有效提高增氧机工作效率、降低使用成本,对满足绿色生态渔业发展需求,提升淡水养殖产量和产值具有重要意义。

2017-2021年长江天鹅洲故道鱼类群落结构变化、成因分析及对长江江豚迁地保护的启示

长江天鹅洲故道是长江江豚首个迁地保护区,其中充足而适口的饵料鱼类资源是长江江豚种群健康发展的保障。为此,根据2017年10月2021年4月对长江天鹅洲故道进行的7次鱼类调查数据,结合禁捕前的历史数据,对其鱼类群落结构演变进行了分析,并针对长江江豚饵料鱼的供应状况对天鹅洲故道内鱼类资源管理提出了建议。调查期间,共采集到鱼类57种,其中,蒙古鲌(Culter mongolicus)、鲢(Hypophthalmichthys molitrix)和鳙(Aristichthys nobilis)等大中型鱼类生物量明显增加,而■(Hemiculter leucisculus)和似鳊(Pseudobrama simoni)等小型鱼类生物量呈现下降趋势。鱼类群落优势种逐渐由太湖新银鱼(Neosalanx taihuensi s)、短颌鲚(Coilia brachygnathus)和■等小型鱼类转变为鳙、蒙古鲌和拟尖头鲌(Culter oxycephaloides)等大中型鱼类,尤其是新近出现的拟尖头鲌种群发展迅速。同时,短颌鲚和■等小型鱼类的体重在减小,而鲢、鳙等大中型鱼类规格在持续提高。长江江豚以小型鱼类和大中型鱼类的幼鱼为食,其资源下降将威胁长江江豚种群的维持和发展。为保障天鹅洲故道内长江江豚的食物供应,建议适当地捕捞鲢、鳙、蒙古鲌和拟尖头鲌,减缓鲢、鳙对小型鱼类的食物竞争压力,以及降低蒙古鲌和拟尖头鲌对小型鱼类的捕食压力;同时丰水期加强故道与长江的连通,引入更多长江干流繁殖的小型鱼类资源;并通过建设人工鱼巢以改善故道内■等产粘性卵小型鱼类的繁殖条件,增加小型鱼类资源量。

基于模糊AHP-DEMATEL的小型木质海洋渔船安全风险评估

为了降低小型木质海洋渔船安全事故风险,构建小型木质海洋渔船安全风险评估指标体系,对影响渔船安全的渔船因素及其船员因素进行综合分析。运用模糊AHP-DEMATEL评价方法建立小型木质海洋渔船安全风险评估模型,并对模型进行验证。结果表明:模糊AHP-DEMATEL方法评估结果与专家的主观判断结果较为一致,建立的模型能够在一定程度上反映出小型木质海洋渔船的安全风险状况,具有较高的可行性。

水电站退出生态修复研究——以桐梓河金阳电站为例

为全面落实国家长江大保护的要求,坚持生态优先,绿色发展,共抓大保护,不搞大开发,贵州赤水河小水电清理整改工作持续推进。本文以赤水河支流桐梓河近河口的金阳电站拆除及生态修复工程为例,通过分析电站拆除的生态影响及修复的必要性,结合电站建设河段实际生态环境问题,确定生态修复范围,并合理进行分区,采用库内清淤、河道内及河岸带生态廊道修复、沿岸陆域生态修复、纵向连通性恢复等人工修复措施,为自然恢复创造条件,加速恢复进程、提升恢复效能,营造适宜鱼类栖息的场所,消除电站对鱼类栖息地及种类组成的影响,恢复杨家园至桐梓河汇口天然河道,增加鱼类洄游空间和栖息地,为类似的小水电清理整改工程提供借鉴。

小型海洋渔船在检验管理中存在的问题及改进建议

文章指出了山东省东营市在海洋渔船检验工作存在的检验手段落后、检验人员技术不过硬、渔船所有人不能办理变更过户手续、渔船发动机更换频繁、部分养殖渔船注销无法检验和其他困难等问题,提出了对渔业船舶检验工作要完善条例并制定标准、完善法规并规范制度、针对问题下放权限、健全机构提高待遇、加强培训提高素质等建议,可供有关部门在决策时参考。