Fish Community Structure Research Articles

Reef fish community structure along the southeastern US Atlantic continental shelf break and upper slope appears resistant to increasing lionfish (Pterois volitans/miles) density

Temperate reefs host diverse fish communities along the southeast United States Atlantic coast (SEUS), yet the sustainable management of reef fishes faces myriad challenges. One challenge has been the introduction of Indo-Pacific lionfish (Pterois volitans/miles; hereafter "lionfish"), which have spread quickly throughout the SEUS since their introduction in the late 1900s. We analyzed long- term (2001–2019) video data along the continental shelf break and upper slope (45–125 m deep) of the SEUS to assess changes in lionfish densities over time, characterize reef fish community structure, and determine if native reef fish community structure has changed due to lionfish. Lionfish densities increased substantially during the study, from zero individuals observed in 2001 to approximately 1.2 individuals observed per 100 m 3 (and present in all included transects) by 2019, yet no fish community metrics were negatively related to lionfish density. Demersal habitat influenced fish community structure more than any other variable examined, with more individuals and different fish communities occurring on high-relief compared to low-relief hardbottom habitats. The effects of latitude, depth, and bottom temperature on reef fish community structure were generally weak or nonexistent. Although previous empirical work has found that lionfish negatively affect native fishes at small scales (<30 km2), it is unclear why we did not find similar results in our larger- scale study. It may be related to vagaries of the spatial scale of observation, lionfish effects being primarily limited to high- relief habitats, time lags, or lionfish densities not being high enough yet to cause observable ecological effects.

Environmental drivers of upper mesopelagic fish assemblages in the Benguela Upwelling System

The Benguela upwelling system is one of the most productive marine ecosystems in the world; however, little is known about the community structure of mesopelagic fishes in its northern (nBUS) and southern (sBUS) subsystems. We analyzed around 1900 specimens from 13 stations in the nBUS and 11 stations in the sBUS during the austral summer and found 88 species and 24 families of mesopelagic fishes. Seven distinct assemblages characterized by water mass, oxygen concentration in the surface layer, and chlorophyll concentrations between 50 and 100 m were identified. The stations belonging to the nBUS shelf assemblage were low in oxygen concentration, had a mean abundance of 0.064 ind. 10 m-2, and were represented exclusively byDiaphus dumerilii. The sBUS shelf assemblage had a mean abundance of 15.00 ind. 10 m-2andMaurolicus walvisensisdominated. Two sBUS offshore assemblages had a mean abundance of 1.12 and 9.48 ind. 10 m-2. The most abundant taxa within the groups wereHygophum hanseni,Cyclothonespp., andD. meadi. Three nBUS offshore clusters had an abundance of 10.21, 11.88, and 14.19 ind. 10 m-2, andD. hudsoniprevailed in 2 groups, whileM. walvisensisdominated the third group. Our study provides insight into the environmental factors that drive the composition of mesopelagic fishes on the shelf and in the upper pelagic zone in these highly productive subsystems. Possible future changes in these subsystems, such as an expansion of the oxygen minimum zone, can thus be expected to affect certain mesopelagic taxa that are essential for the food web of the subsystems.

城镇化背景下深圳典型流域鱼类群落特征及驱动因子研究

PDF HTML阅读 XML下载 导出引用 引用提醒 城镇化背景下深圳典型流域鱼类群落特征及驱动因子 DOI: 10.5846/stxb202106071510 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 深圳市主要河流水生态监测与评价项目（2019-07-233） Characteristics of fish communities and driving factors under urbanization in typical river basins in Shenzhen City, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:理解城镇的快速发展对河流鱼类群落结构的影响，是城镇河流科学管理和生物多样性保护的关键基础。研究于2019年丰水期（8月）和枯水期（11月），选取我国城镇化典型城市-深圳域内两个处于不同城镇化程度的代表性流域，应用多重统计方法比较分析了流域间鱼类群落结构的差异，并探讨了驱动鱼类群落变异的关键环境要素。结果发现，城镇化程度高的观澜河流域其鱼类种类组成、优势类群、生物多样性指数与城镇化程度低的坪山河流域有明显差别。具体表现为：城镇化程度高的流域土著敏感种类如异鱲、吸鳅等几近消失，优势类群为外来入侵耐受种类，其物种多样性显著低于城镇化程度低的流域（P<0.05）。同时，外来鱼类在城镇河段其数量占比平均达92.5%，广泛分布于深圳城镇河流中。在环境因素方面，城镇化程度高的观澜河流域水体理化指标总氮、总磷、氨氮、化学需氧量、生化需氧量、高锰酸盐指数均显著性高于城镇化程度低的坪山河流域（P<0.05）。基于Bray-Curtis距离的冗余分析显示：城镇用地占比和总氮是影响观澜河和坪山河流域鱼类群落差异的主要因素。城镇化进程中河流生境的改变已影响到土著鱼类的生物多样性。因此，推动以恢复土著鱼类生物多样性的河流生态治理与保护是今后水生态目标管理的重要方向。 Abstract:Understanding impacts of rapid urbanization on structure of river fish communities is the key basis for scientific management and biodiversity conservation for urban rivers. We selected two representative basins with different degrees of urbanization in the typical urbanized city, Shenzhen City, China. Field sampling was conducted in both wet (August) and dry (November) seasons in 2019. We compared and analyzed the differences of fish communities between the two basins using the multiple statistical methods, and explored the key environmental factors driving the variations of fish communities. Results showed that species composition, dominant species, and biodiversity of fish in the highly urbanized Guanlan River Basin were significantly different from those in the less urbanized Pingshan River Basin. In particular, the sensitively indigenous fish species such as Schistura fasciolatus and Parazacco spilurus disappeared while the invasive tolerant species were the dominant species in the highly urbanized basin. Fish biodiversity was significantly lower in the highly urbanized basin than the less urbanized basin (P<0.05). Meanwhile, non-native fish species had spread rapidly in urbanized rivers of Shenzhen City, which accounted for more than an average of 92.5% in the urbanized river sites. For environmental factors, total nitrogen, total phosphorus, ammonia, chemical oxygen demand, biochemical oxygen demand, and permanganate index in the highly urbanized Guanlan River Basin were significantly higher than those of the less urbanized Pingshan River Basin (P<0.05). Redundancy analysis based on the Bray-Curtis distance showed that the proportion of urban land and total nitrogen were the main factors affected the difference of fish communities in the Guanlan and Pingshan River Basins. Changes of river habitat from urbanization reduced biodiversity of the native fishes. Thus, restoring native fish biodiversity in river ecological management and protection is the important direction of aquatic objective-based management. 参考文献 相似文献 引证文献

ASSESSMENT OF THE SPECIES STRUCTURE OF JUVENILE FISH COMMUNITIES IN THE DNIESTER RESERVOIR

The study of the qualitative and quantitative components of the structure of juvenile fish communities, as well as their distribution in the reservoir is an important component of comprehensive ichthyological studies of fish biology and ecology in specific hydroecosystems, especially under conditions of anthropogenic impact. Such studies are important for the development of measures to preserve the biodiversity of aquatic ecosystems, allow to assess the current species composition of fish and the effectiveness of spawning of individual species in the current year, to develop biological substantiation of biological reclamation measures and to predict future catches. The article analyzes the results of ichthyological studies conducted in different parts of the Dniester reservoir during 2016-2020. It was shown that the conditions of natural reproduction of native fish fauna in the Dniester reservoir are unstable. During the study period, juveniles of 24 fish species were recorded in the Dniester reservoir, with 3 species present in the catches every year. In unfavourable hydrological years, the dominance of juvenile fish communities of low-value species (silver carp) was noted in the reservoir, while the number of juveniles of valuable rare and commercial species remains at a very low level. The problem of increasing the fish productivity of the Dniester reservoir cannot be solved without the purposeful formation of the fish fauna composition by introducing into the reservoir the fish-planting material of native fish obtained as a result of artificial reproduction

江西柘林水库鱼类群落结构及功能多样性分析

PDF HTML阅读 XML下载 导出引用 引用提醒 江西柘林水库鱼类群落结构及功能多样性分析 DOI: 10.5846/stxb202106031466 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2019YFD0900603）；财政部和农业农村部：国家现代农业产业技术体系资助（CARS-46）；中国水产科学研究院基本科研业务费院级湖库增殖渔业创新团队项目（2020TD57） Community structure and functional diversity of fishes in Zhelin Reservoir, Jiangxi Province Author: Affiliation: Fund Project: National Key Research and Development Program of China (No.No.2019YFD0900603); Supported by China Agriculture Research System of MOF and MARA（CARS-46）; Central Public-interest Scientific Institution Basal Research Fund，CAFS (NO.2020TD57) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解江西柘林水库鱼类群落结构和多样性的时空变化特征，研究鱼类物种多样性和功能多样性的关系，于2020年9月至2021年4月在该水库调查分析了鱼类物种组成、优势度及群落物种多样性和功能多样性。结果表明，共采集鱼类53种，分属于5目12科36属。其中，鲤形目（38种）种类最多，占调查物种数的71.69%，柘林水库上、中、下游库区分别采集到鱼类36、40和32种，各库区均以鲤形目鱼类为主，分别占采集物种数的72.97%、85.00%和75.00%。优势物种主要是䱗（Hemiculter leucisculus）、鳙（Aristichthys nobilis）和黄尾鲴（Xenocypris davidi），重要种主要是草鱼（Ctenopharyngodon idella）、鲢（Hypophthalmichthys molitrix）、鳊（Parabramis pekinensis）、鲫（Carassius auratus）、蒙古红鲌（Erythroculter mongolicus）等。鱼类群落结构季节性差异大于空间格局差异，主要表现为秋季和冬季之间；生物多样性指数Margalef和功能丰富度指数在上游修河水域相对较高，鱼类物种多样性和功能多样性空间格局差异性大于时间尺度下的差异性。物种多样性与功能多样性的回归分析结果显示，功能丰富度与物种多样性指数之间存在显著的正相关关系；功能冗余度与各物种多样性之间呈现负相关关系，说明物种数的增加导致了库区鱼类功能丰富度的增加和功能冗余度的降低，而功能均匀度未发生明显的变化，主要原因为调查区域内拥有不同功能性状的鱼类群体之间在个体数比例上呈现不均匀分布的模式，这一结果预示着拥有较多物种的群落生态位重叠度相对较低，生态系统受干扰后的恢复能力较差。总体而言，保护鱼类生物多样性和维护生态系统的稳定性应该通过调控鱼类种群结构达到提高鱼类群落冗余度以及资源和生境可用性的目的。 Abstract:To understand the spatial and temporal variation of fish assemblage structure and biodiversity, as well the relationships between fish taxonomical diversity and functional diversity, species compositions, the dominant species, taxonomical and functional diversity of fish communities which were captured from Zhelin Reservoir from September 2020 to April 2021 were investigated and analyzed. The results showed that a total of 53 fish species belonging to 5 orders, 12 families, and 36 genera were sampled with dominant Cyprinidae accounting for 71.69% of the total species. Among the reservoir spatial scales, 36, 40 and 32 fish species which accounting for 72.97%, 85.00% and 75.00% of the total sampled species were captured from upper-, middle- and low-reach, respectively. Hemiculter leucisculus, Aristichthys Nobilis and Xenocypris davidi were dominant species, while Ctenopharyngodon idella, Hypophthalmichthys molitrix, Parabramis pekinensis, Carassius auratus and Erythroculter mongolicus were main species in Zhelin Reservoir. The analysis of PERMANOVA (Permutational Multivariate Analysis of Variance) using the fish assemblage matrixes showed that the seasonal variation of species compositions was more significant than the spatial scale, and the variations were mainly performed between two seasons of antum and summer. Meanwhile, biodiversity indexes and functional diversity indexes of fish assembalges performed relative higher variations among spatial scales than temporal scales. Margalef index were relatively higher in the Xiuhe River than those in other water sites, while the indexes of Shannon, Simpson and Peilou indexes showed no variation among the reaches. Functional richness possessed relative higher level in upper reach than midlle and lower reaches, while functional evenness and functional disperse performed non changes among spatial scales. Functional redundancy had no variation among spatial and temporal scales. Regression analyses showed significant positive relationships between the biodiversity index of functional richenss and functional disperse with each taxonomical diversity index, while there were negative relationships between functional redundancy and taxonomical diversity indexes, which implying the increase of species richness led to the increase of the functional richness and decrease of functional redundancy. However, functional evenness did not change obviously which can mainly be explained by the disproportionate individuals of different fish functional groups. The results implied that interference resulted in a lower niche overlap of fish community with high species richness and lower ecosystem recovery ability. In general, the species diversity level of Zhelin Reservoir is lower and the anti-interference ability of this ecosystem is relatively weaker. To protect fish biodiversity and maintain the stability of the ecosystem, it is necessary to improve the fish community redundancy and the availability of resources and habitats by regulating the fish population structure. 参考文献 相似文献 引证文献

鱼类对海洋升温与酸化的响应

自工业革命以来, 空气中人为排放CO₂量增加, 引起温室效应, 导致地球表面温度升高和海水升温；同时, 由于海-气界面气体交换, 大气中CO₂部分溶解于海洋, 引起海洋酸化。海洋升温加快鱼体内生化反应和代谢速率, 并通过影响生长、觅食和繁殖等生命过程中能量供给, 间接影响到鱼类种群分布、群落结构及生态系统的功能。而海水酸化会干扰海洋鱼类仔稚鱼的感觉和行为, 增加其被捕食率, 并削弱其野外生存能力, 可能威胁自然种群补给量。综述了海洋升温、海洋酸化及其两者共同作用对海洋鱼类的影响, 为预测鱼类响应全球海洋环境变化的响应趋势提供相关依据。;Since the Industrial Revolution, the increase of anthropogenic carbon dioxide (CO₂) emissions has led to the greenhouse effect and the rise of the surface temperature on the earth and in the ocean. At the same time, ocean is absorbing more CO₂ that causes ocean acidification. Ocean warming accelerates the biochemical reaction and metabolic rate of fish and indirectly influences the distribution of fish population, community structure and ecosystem function by affecting the energy supply in the life process such as growth, foraging and reproduction. Ocean acidification may impact the sensory and behavior of marine fish, increase their predation rate, and weaken their ability to survive, which will threaten the supply of natural population. The effects of ocean acidification and warming on fish have complex interactions such as synergistic accumulation and antagonism. In this paper, the impact of ocean warming, acidification and their combined effects on marine fish are introduced successively, which maybe provide relevant basis for predicting the variation trend of fish in response to climate change.

种间互作对雷州湾海域鱼类群落结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 种间互作对雷州湾海域鱼类群落结构的影响 DOI: 10.5846/stxb202108212330 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划"蓝色粮仓科技创新"重点专项资助（2020YFD0901103）；南方海洋科学与工程广东省实验室（湛江）资助项目（ZJW-2019-06） Importance of species interactions in structuring fish community of Leizhou Bay waters, northern South China Sea Author: Affiliation: Fund Project: The National Basic Research Program of China (973 Program),其他 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:从鱼类种间互作及其生态网络特征视角研究鱼类群落结构特征，对解析多鱼种共存机制和基于群落水平的多鱼种资源管理均具有重要意义。为分析鱼类资源利用的竞争互作对群落结构稳定性的影响，根据2016-2018年8个航次的雷州湾海域底拖网调查的鱼类数据，将空间生态位重叠理论和生态网络建模相结合，从种间互作的角度应用加权聚类系数C、加权平均路径长度A、关联度Co等指标分析鱼类的群落结构。结果表明：①鱼类生态位重叠所形成的种间互作网络季节变动较大，而年度变动则相对较小，共包含鱼类58-122种，种间互作的关系数量1318-7103。②雷州湾海域鱼类群落内种间互作密集，聚合程度高（C介于0.84-0.98）且能量传递效率高（A介于0.02-0.09），呈现互作弱化之趋势（Co介于0.32-0.48），群落结构总体较稳定。③小尺度范围（20°40'-21°00'N，110°30'-110°45'E）内，鱼类群落内种间互作特征是维持多种鱼类共存的重要内因。该特征表现为季节和年度的变化总体上相似，种间直接关联程度与种间互作强度呈正相关（P<0.01），而局部聚合程度与种间直接关联、互作强度均呈负相关（P<0.01）。本研究可为鱼类群落结构稳定性的量化评价和资源养护的管理规划提供参考依据。 Abstract:The interactions between fish species and their roles in the ecological network on structuring the fish community is a matter of great concern not only for understanding the species coexistence, but also for the multispecies fishery management and conservation at the community level. The data from the bottom trawl surveys of eight cruises in Leizhou Bay waters northern South China Sea during 2016 and 2018 were applied to analyze how the species interactions (interspecific competition in limited resources and space) affected the stability of fish community structure in seasons and years. Combining theories on spatial niche overlap and the ecological network modeling, six indicators such as the weighted clustering coefficient (C), weighted average path length (A), connectance (Co), degree (K), weighted node strength (Si), and locally weighted clustering coefficient (Ci) were respectively applied to measure the degree of community aggregation, the overall energy transfer efficiencies between species, interspecific connectivity, the degree of directly interspecific associations, the intensity of species interactions, and the degree of local aggregation between species. And then we analyzed the importance of species interactions in structuring fish community of Leizhou Bay waters. The results showed that:①the network of species interaction which formed by spatial niche overlap of fishes varied more widely in seasons, but comparatively minor between years, including 58-122 kinds of fishes, and 1318-7103 lines (links between species interactions). ②The fish community was characterized with the intensive interactions, high degrees of aggregation (C ranged between 0.84 and 0.98), high energy transfer efficiencies (A ranged between 0.02 and 0.09), with a weakening tendency of species interactions (Co ranged between 0.32 and 0.48) from 2016 to 2018. The fish community of Leizhou Bay waters was kept in a state of stability in all. ③At the local small scale (20°40'-21°00'N, 110°30'-110°45'E), traits of species interactions of the fish community were similar on the seasonal and annual scale. Two traits were the important internal factors driving the coexistence of multiple fish species in the Leizhou Bay waters. The first was the degree of directly interspecific associations which was positively correlated with the intensity of species interactions (P<0.01). And the second was the degree of local aggregation which was negatively correlated with both the degree of directly interspecific associations and the intensity of species interactions (P<0.01). This study provides clues for the quantitative analysis on the stability of fish community structure and planning of effective coastal fishery resources management and conservation. 参考文献 相似文献 引证文献

Co-opting small-scale fishers’ knowledge with scientific data to improve understanding of fish community structures in the Lower Komati River, South Africa

Context In developing countries, fish data might be lacking and expensive to collect. Fisher’s local ecological knowledge (LEK) has been identified as important to complement scientific data gaps. However, consensus and divergences between both methods have not been extensively studied. Aims This paper compares local fishers’ LEK and scientifically sampled data on fish species composition, ecological preferences, and wellbeing in the Lower Komati River, South Africa. Methods Key informant interviews (n = 6), field tracking (n = 5) and participatory mapping (n = 22) were undertaken to capture fishers’ LEK and produce maps showing fishing points. Two science-led fish surveys in six sites were also undertaken between August 2019 and December 2019 by using an electrofishing method. Key results The fishers’ LEK and survey data showed similar patterns of occurrence of Micralestes acutidens, Coptodon rendalli, Oreochromis mossambicus and Labeo cylindricus. Comparing fishers’ catch estimates and survey catch showed that there is no significant difference (P &gt; 0.05) in abundance on the two most sampled species by using ANOVA. Conclusion Differences between the two methods were observed in assessing the river and fish’s wellbeing. Implication The similarities and differences were identified as opportunities for small-scale fisheries and scientists to co-identify ecosystem management strategies that are congruent to the local environment.

The characteristics of spatial-temporal distributions of fish resources in Lake Jingpo based on hydroacoustic assessment

2020年5、7和10月，采用多网目复合刺网调查和水声学探测相结合的方式对镜泊湖鱼类群落时空动态和资源量进行调查.渔获物调查共采集鱼类4目6科29种，其中鲤科鱼类最多，主要经济鱼类为鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys nobilis）、蒙古鲌（Chanodichthys mongolicus）、瓦氏雅罗鱼（Leuciscus waleckii）、鲤（Cyprinus carpio）、翘嘴鲌（Culter alburnus）.蒙古鲌和（Hemiculter leucisculus）为优势种.水声学探测结果表明，镜泊湖鱼类密度在春季、夏季和秋季分别为836、7216和2724 ind./hm²，其中夏季鱼类密度最高且主要集中于中部和南部区域，春季和秋季鱼类密度则呈现从南至北递减的趋势.春、夏、秋季鱼类的平均目标强度为-43.4、-50.0和-46.5 dB，估算的平均全长分别为34.0、18.0和25.2 cm，推算的平均体重分别为272.7、43.7和135.2 g.结合各季节平均密度，估算出春、夏、秋季镜泊湖鱼类资源量分别为2052、2835和3313 t.镜泊湖鱼类密度与环境因子之间的冗余分析结果表明，水体总悬浮物、叶绿素a、水温和溶解氧是影响鱼类群落结构变化的关键环境因子.从水声学探测和刺网调查的结果来看，镜泊湖渔获物小型化问题突出，鱼类资源呈现衰退趋势，渔业资源的不合理利用是造成镜泊湖鱼类资源衰退的主要因素.因此建议强化对自然捕捞的管理，严格控制捕捞数量和规格，保障鱼类资源自然增殖，结合牡丹江流域污染防治、改善鱼类栖息地环境等鱼类生境修复措施，以促进鱼类资源的恢复.;In May, July and October 2020, a combination of multi-mesh gillnet and hydroacoustic survey was undertaken to investigate the characteristics of spatial-temporal distributions of fish resources of Lake Jingpo. A total of 29 fish species, belonging to four orders and six families, were collected during the survey. The main economic fish are Hypophthalmichthys molitrix, Aristichthys nobilis, Chanodichthys mongolicus, Leuciscus waleckii, Cyprinus carpio, and Culter alburnus. The dominant species are Chanodichthys mongolicus and Hemiculter leucisculus. The average fish density was 836 ind./hm² in spring, 7216 ind./hm² in summer and 2724 ind./hm² in autumn. In summer, fish mainly inhabited in the central and southern regions. In spring and autumn, the species density showed a decreasing trend from the south to the north. The average target strengths were -43.4, -50.0 and -46.5 dB in spring, summer and autumn, the estimated average total lengths 34.0, 18.0 and 25.2 cm, and the estimated average weights 272.7, 43.7 and 135.2 g, respectively. The estimated average density of fish resources in Lake Jingpo was 2052, 2835 and 3313 t in spring, summer and autumn, respectively. The results of redundancy analysis between the fish density and environmental factors in Lake Jingpo showed that the total suspended solids, chlorophyll-a, water temperature and dissolved oxygen were the key environmental factors affecting the changes of fish community structure. According to the results of hydroacoustic and gillnet survey, the problem of miniaturization of catches in Lake Jingpo is prominent, and the fish resources are declining. Irrational utilization is the main factor resulting in the decline of fishery resources in Lake Jingpo. We recommend the relevant authorities strengthen the management of natural fishing strictly control the number and size of fishing, ensure the natural proliferation of fish resources, and integrate the pollution control of the Mudanjiang River Basin and the improvement of fish habitat environment and other fish habitat restoration measures, in order to promote the recovery of fishery resources.

Environmental correlates of elasmobranch and large fish distribution in a river-dominated estuary

Coastal areas serve as vital habitat for many marine fishes and often host broad gradients of environmental conditions that result in diverse species assemblages. Understanding the influence of environmental variables on the distribution and abundance of fishes is especially important for devising appropriate management strategies. We documented large fish community structure in the Apalachicola Bay system from 2018 to 2021 using fishery-independent longline and gillnet surveys. Spatiotemporal variation in fish assemblages was evaluated with permutational multivariate ANOVA, while community- and species-level habitat relationships were described across gradients of environmental variables with non-metric multidimensional scaling and generalized additive models. We captured 5085 fishes from 17 elasmobranch and 33 bony fish species, with gafftopsail catfish Bagre marinus, blacktip shark Carcharhinus limbatus, Atlantic sharpnose shark Rhizoprionodon terraenovae, and hardhead catfish Ariopsis felis comprising 82.1% of the total catch. Fish communities varied spatially throughout the system, and changes in these communities were most strongly correlated with gradients in salinity, clarity, and depth. We documented higher species richness and density of young elasmobranchs in our surveys compared to adjacent systems, supporting past suggestions that this area serves as important juvenile shark habitat. We suggest that flow from the Apalachicola River, transporting nutrients to the system and supporting numerous environmental niches across spatiotemporal scales, plays an influential role in maintaining the elevated diversity and density of elasmobranchs observed in this study.

Plankton dynamics and their relationship with environmental factors shape fish community structure in fluvial ecosystem: A case study

Plankton dynamics and their relationship with environmental factors shape fish community structure in fluvial ecosystem: A case study

Acoustic correction factor estimate for compensating vertical diel migration of small pelagics

Differences in acoustic estimates of small pelagic fish biomass, due to data acquisition during daytime and nighttime surveys, have been recognized for many years as a problem in acoustic surveys. In the absence of a single rule for all species and for all locations, some expert groups identified specific time intervals for acoustic data acquisition in relation to the schooling behavior of the target species. In the Mediterranean Sea, the research groups working in the MEDIAS (Mediterranean International Acoustic Survey) agreed on the importance that acoustic sampling are conducted only during day-time. Only when available time does not permit to complete the survey during daytime, data collection might be extended. In this case, working on data collected during both daytime and nighttime, a bias may occur in the biomass estimates. In order to evaluate and correct such bias, specific experiments were performed in some geographical sub-areas of the Mediterranean Sea. The data analysis allowed the estimation of a mean correction factor for the Strait of Sicily, where five surveys were carried out in different years. The correction factor was estimated also for the Adriatic Sea, Tyrrhenian Sea and Northern Spain; the observed variability among areas highlighted the importance of the spatial and temporal coverage of the survey area in order to obtain reliable estimates of the correction factor. Further studies are necessary to improve the interpretation of the obtained estimates in relation to area-related peculiarities such as zooplankton composition and abundance along with small pelagic fish community structure.

Ichthyofaunal diversity with relation to environmental variables in the snow-fed Tamor River of eastern Nepal

Tamor River in eastern Nepal supports diverse hill stream fishes. From winter, spring, summer, and autumn of 2020, we investigated the ichthyofaunal diversity with environmental variables in the snow-fed Tamor River covering four seasons (winter, spring, summer, and autumn) and field surveys were carried out in January, April, July, and October 2020. We used two cast nets of different sizes, one with a mesh size of 2 cm, 6 m diameter and 6 kg weight and another having 0.5 cm, 3 m diameter and 2 kg weight. In addition, monofilament gill nets with mesh sizes of 6, 8, and 10 were used for fish sampling. A total of 6,373 fish individuals representing 28 species belonging to three orders, seven families, and 16 genera were recorded. One-way permutational multivariate analysis of variance (perMANOVA) on the Non-metric Multidimensional Scaling (NMDS) showed no significant (P &gt;0.05) difference between winter, spring, and autumn season but summer season showed significant (P &lt;0.05) difference from winter, spring, and autumn seasons. Furthermore, one-way analysis of variance on redundancy analysis (RDA) vindicated that among the selected parameters, pH, air temperature and total hardness were the influencing factors (P &lt;0.05) to determine the fish community structure in Tamor River.

Fish Community Structure in River Ossiomo, Niger Delta, Nigeria in Relation to Some Selected Environmental Variables

In the past decade, it has been reported that water quality of rivers are deteriorating increasingly. In this study we examined the state of River Ossiomo to assess the current health of the river for a period of 24 months from April 2019 to March 2020, then July 2020 to May 2021 in three well marked out stations. The study was to determine the relationship between environmental variables and fish species assemblage in the river. From the results of the physico-chemical variables, the mean values of pollution indicating physico-chemical variables such as sulphate (1.26+0.32mg/l) and total suspended solids (TSS) (5.53+1.89mg/l) were higher in station 2. On the other hand, pH (5.94+0.48), DO (8.64+1.57mg/l), turbidity (7.48+7.63NTU), TDS (29.64+14.65mg/l) and phosphate (0.43+0.31mg/l) mean values were highest in station 1. Conductivity (70.87+26.42µS/cm) and nitrate (0.49+0.34mg/l) mean values were highest in station 3. Further, dissolved oxygen (DO) was higher in station 1, the reference station. The analysis of variance (ANOVA), we performed for the physico-chemical variables revealed that temperature, conductivity, DO, total dissolved solids (TDS), alkalinity, TSS, sulphate, phosphate and nitrate were significantly different among the three stations sampled (P&lt;0.05), while pH, BOD and turbidity were not significant among the three stations sampled (P&gt;0.05). The result of the principal component analysis showed that conductivity was positively associated with station 3, and temperature, TDS and alkalinity were negatively associated with stations 1 and 2. A total of 2,324 fish individuals belonging to 29 taxa were recorded in the entire study period. Station 1 harbours more fish species (1018), followed by station 2 (809), and we recorded the lowest number of fish individuals in station 3 (497). Auchenoglanis occidentalis was the most preponderant fish species probably occasioned by its level of adaptation to prevailing environmental conditions in the study river. The least abundant fish species was Synodontis eupterus.The canonical correspondence analysis we used in visualizing the relationship between fish species and physico-chemical variables showed that fish taxa such as Distichodus brevipinni, Cteropoma kinsleyae, Tilapia zillii, Malapterarus electricus, Mormyrus engystoma, and Synodontis nigita that were positively associated with pollution indicating physico-chemical variables were suggested as indicators for monitoring riverine health in the Niger Delta area of Nigeria. We recommend that more detailed studies should be carried out in River Ossiomo to confirm this result. However, this study serves as a baseline study in the present study area.

Why body size matters: how larger fish ontogeny shapes ecological network topology

Ontogenetic development can strongly shape species interactions. Yet, rarely is stage‐structure considered when analyzing species interaction networks, particularly networks that can account for more than feeding relationships. Here, we assess 1) if body size or trophic level regulate the importance of species' ontogeny on their interactions and 2) how including relevant stage‐structure affects the topology of species interaction networks. We use a count‐based inferential method to create networks from adult and juvenile fish count data and test stage‐structure importance by comparing a model that includes stage‐structure for all species against models that include stage‐structure only for larger fishes and only for piscivorous fishes during network construction. While the inferential method we use cannot differentiate between different types of interactions, it can account for different interaction types within a network as a pairwise interaction is inferred when one species influences the abundance of another. Next, we use graphlet‐based techniques to test if including stage‐structure alters overall network topology and a linear model to measure if adult‐juvenile size differences drive interaction differences at a species‐level. We find that the model that includes stage‐structure only for larger fishes outperforms other stage‐structured models including the model with only piscivore stage‐structure, and that larger differences in body size among juveniles and adults lead to greater interaction dissimilarities. Moreover, we find topological differences between inferred networks that only include adults and those that account for the stage‐structure of larger species. Overall, our study demonstrates how stage‐structured topological changes can be measured using inferred interaction networks and illustrates how larger species' juveniles fundamentally shape the structure of stream fish communities.

Fish community structure along altitudinal gradients with relation to environmental variables in Ratuwa River of Eastern, Nepal

Studies on fish community structure along altitudinal gradients of rivers are lacking in Nepal. This study was carried out to gauge the fish diversity and composition along elevational gradient in Ratuwa River. The altitudinal gradient varies between 70 m to 1300 m. Fish samples were collected based on habitat representativeness from April (spring) 10-18, July (summer) 10-18, October (autumn) 10-18, 2020 and January (winter) 10-18, 2021. A total of 3447 specimens representing 4 orders, 14 families and 36 species were identified. Both fish diversity and abundance of studied ichthyofauna vary with altitudinal gradient. The present study affirmed that fish species of Opsarius bendelisis, Schistura multifasciatus, Garra annandalei, Brachydanio rerio, Aspidoparia morar, and Schistura scaturigina are the major contributory species (&gt;1%) for both space and time spectrums. Fish community structure testing for both to space and time showed significant difference in spatial spectrum (R=0.72, P&lt;0.01) but no significant difference in temporal variation (R=-0.034, P&gt;0.05). The present results hinted that fish assemblage structure varied significantly from low to high elevations, altitude, water temperature, water velocity, dissolved oxygen and pH was found as major influential factors (P&lt;0.05) for species distribution.

Relationships between environmental conditions and fish assemblages in the Lohore River of Dailekh, Western Nepal

The Lohore River is one of the important riverine ecosystems of Dailekh which support diverse aquatic communities. The present study was carried out to assess the fish diversity status with relation to environmental conditions in both to space and time. The survey was conducted at three different sampling stations in three different seasons. For the fish sampling, two cast nets of different mesh sizes were used, one having large mesh size of 2 cm, 6 m diameter and 6 kg weight and another having mesh size of 0.5 cm, 3 m diameter and 2 kg weight. Moreover, drag net and gill net were also used to collect the fish samples. A total of 11 fish species belonging to 2 orders, 3 families and 7 genera. Results from the similarity percentage analysis (SIMPER) suggested that fish species of Puntius gelius, Schizothorax plagiostomus, Tor chelynoides and Schistura sovana were major contributing species each contribute more than 9%. An analysis of similarity (ANOSIM) pointed that fish community structure in the Lohore River differ in spatial scale (p&lt;0.01) but not in temporal scale (P&gt;0.01). Water temperature, dissolved oxygen and water velocity was found as influential factors for fish species distribution.

Diversity, abundance and community structure of fishes in the lower part of the Euphrates River Southern Iraq

Diversity, abundance and community structure of fish species in the lower part of the Euphrates River was investigated during May 2016 to April 2017. Three stations were selected to conduct the work. Monthly variance of water temperature ranged from 11ºC in January and February to 31ºC in August, turbidity differs from 2.31 in June to 24.10 NTU in November. The overall values of hydrogen-ion differ from 7.52 in April to 8.27 in November and December. The overall values of salinity in the work area were 0.91 ‰ in October to 1.52 ‰ in May. Several fishing methods were used to collect the samples of fishes. A total of 4380 specimens' of fish were collected included 23 fish species belonging to 23 genera and 11 families, ten of them represented native fish species, eight alien fish species and five marine species. Oreochroims aureus was the most abundance species formed 34.27 % of the total number then Liza abu (24.66 %) of the total number of species and Carassius gibelo (14.36 %). Values of three dominate species (D3) was 73.29 %. The mean values of diversity index (H) in the study area ranged from 1.11 to 1.92, evenness index (J) from 0.53 to 0.90 and richness index (D) from 1.15 to 2.33. The study showed the dominance of small species of exotic and native fish in the study area and the scarcity of large economic species due to the overfishing.

Reef fish community on Sabira Island, Kepulauan Seribu Regency, DKI Jakarta

Sabira Island is an island close to Jakarta Province but still has good water conditions and a coral reef ecosystem with a high level of diversity. The condition of the coral reef ecosystem affects the community structure of the reef fish there. This study aims to determine the community structure of the reef fish on Sabira Island. The research was conducted in August 2019 on Sabira Island, Kepulauan Seribu Regency, DKI Jakarta Province. Observations of reef fish were carried out using the Underwater Visual Census method at four observation stations. There were 47 species of reef fish found on Sabira Island from 12 families. The total reef fish found were 1315 individuals, consisting of 79 indicator fish, 417 individual target fish, and 819 major fish. The highest diversity index value on Sabira Island was found at the South Station, with a diversity index value of 2.39. Based on the community structure index at the four observation stations, the reef fish community’s condition on Sabira Island is still good ranging from unstable to stable condition with moderate diversity and low dominance index values.

Zooplankton and fish community structures in interconnected lakes

Zooplankton and fish community structures in interconnected lakes