我国伊犁河鱼类群落结构及外来鱼类适生性

2012-2019年,在我国伊犁河流域的6个断面开展了鱼类群落结构调查,结果显示我国伊犁河流域现有鱼类共计29种,大多属于鲤形目。鱼类群落组成与20世纪末期相比发生了变化,银色裂腹鱼、短头鲃、银鲫、鲢、北方泥鳅在本研究中未出现,尤其是银色裂腹鱼,截至目前为止的鱼类资源调查中,均无捕获记录。历史研究中未见的乌鳢与大口鲇在本研究中有捕获。外来鱼类的出现率和数量均有所增加。对鱼类群落结构特征进行分析,显示伊犁河流域鱼类群落多样性较低,下游干流和上游支流的鱼类群落结构差异较大。现阶段,我国伊犁河流域主要的优势种外来鱼类有鲤、和鲫。利用最大熵生态位模型（MaxEnt）对鲤、和鲫的适生区域进行预测,与鱼类资源调查获得的鱼类实际分布区对比,显示鲤和在我国伊犁河流域的分布范围与预测结果是吻合的,而鲫在进入伊犁河流域之后开始向上游支流河段扩散。由于这几种外来鱼类在一开始引入的时候未采取管控措施,又具有极强的适应能力,且伊犁河流域的鱼类多样性较小,因此极易形成规模并扩散。外来鱼类的入侵,会对土著鱼类造成巨大的威胁。基于本论文研究结论,应当将已发生生态位漂变的鲫其作为重点关注种类,关注外来鱼类的生活史对策,深入研究外来鱼类的入侵机制和诱因;对上游支流河段的生境进行监测,关注气候和水文变化,尤其是土著鱼类产卵场、索饵场和越冬场的变化,尽可能减小人类活动干扰;对伊犁河流域的鱼类资源进行长期监测,关注鱼类群落结构变化,一旦发现异常及时采取措施;增加对土著鱼类的增殖放流;严格控制进出口贸易和增殖放流时夹带的外来鱼类。维护我国伊犁河流域的生态安全。     

城镇化背景下深圳典型流域鱼类群落特征及驱动因子

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。本研究于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。     

新疆额敏河干流鱼类群落结构及其与环境因子的关系

2016年10月在额敏河干流设置4个监测断面,对该水域鱼类群落结构进行研究。结果表明:调查共采集鱼类3148尾,隶属于3目4科10属,共计11种;额敏河干流的鱼类优势种为鲫(Carassius auratus Linnaeus)、新疆高原鳅(Triplophysa strauchii Kessler)、麦穗鱼(Pseudorasbora parva Temminck et Schlegel)、斯氏高原鳅(Triplophysa stoliczkae Steindachner)和棒花鱼(Abbottina rivularis Basilewsky)。对各个采样断面鱼类群落生物多样性的分析结果表明,第1断面与第4断面多样性指数较高。利用去趋势对应分析(DCA)与冗余分析(RDA),将鱼类群落在空间上分为3组:1、2断面为一组,其余两个断面各占一组。排序结果显示,pH与溶解氧是影响鱼类群落变异的主要环境因素,其次是温度与电阻率。本研究结果初步揭示了额敏河干流鱼类群落结构特征,为该流域鱼类资源的养护及利用提供参考。     

拉萨河鱼类调查及保护

拉萨河是雅鲁藏布江最大的支流, 其鱼类区系为隶属于裂腹鱼亚科、条鳅亚科和科的13 种鱼类以及裂腹鱼属的一个自然杂交种。最近十几年, 由于人类活动的影响, 导致了大量的外来鱼类进入拉萨河水体。文章介绍了2004 年至2006 年对拉萨河鱼类进行采样调查的情况。目前在拉萨河, 鱼类组成包括以往记录的14 种鱼类: 拉萨裂腹鱼Schizothorax waltoni (Regan)、异齿裂鱼 S. o’connori (Lloyd)、巨须裂腹鱼S.macropogon (Regan)、双须叶须鱼 Ptychobarbus dipogon (Regan)、尖裸鲤 Oxygymnocypris stewartii (Lloyd)、拉萨裸裂尻鱼Schizopygopsisyounghusbandi younghusbandi Regan、异齿裂腹鱼和拉萨裂腹鱼的一个自然杂交种、异尾高原鳅Triplophysa stewartii (Hora)、细尾高原鳅T. stenura (Herzenstein)、西藏高原鳅T. tibetana(Regan)、东方高原鳅T. orientalis (Herzenstein)、斯氏高原鳅T. stoliczkae (Steindachner)、短尾高原鳅T.brevicauda (Herzenstein)、黑斑原Glyptosternum maculatum (Regan); 8 种外来鱼类: 鲫Carassius auratus(Linnaeus)、麦穗鱼Pseudorasbora parva (Temminck et Schlegel)、泥鳅Misgurnus anguillicaudatus (Cantor)、黄黝鱼Hypseleotris swinhonis (Gunther)、鲤Cyprinus (C.) caupio Linnaeus、草鱼Ctenopharyngodon idellus(Cuvier et Valenciennes)、银鲫Carassius auratus gibelio (Bloch)、鲇Silurus asotus Linnaeus; 2 个未定种。调查结果表明拉萨河鱼类资源面临的两个主要问题是过度捕捞导致鱼类资源的减少和小型化以及外来鱼类入侵。文章针对这些情况作了分析和探讨, 并对土著鱼类的保护与合理利用提出了一些建议: 合理捕捞、严格禁渔期、控制外来鱼类、保护栖息地等。       

新疆伊犁河不同河段鱼类的物种多样性和优势种

为了了解伊犁河鱼类群落结构和多样性特征, 于2012—2014年连续3年对我国境内新疆伊犁河上、中和下游不同河段进行鱼类资源调查。获得27种鱼类样本, 隶属于6目9科23属。伊犁河中、上游河段主要以斯氏高原鳅、新疆裸重唇鱼、新疆高原鳅和伊犁裂腹鱼等土著鱼类为优势种, 下游河段的优势种主要有鲤、草鱼和鲫等外来种。伊犁河中、上游河段鱼类种类稀少, 大中型鱼类资源稀少, 鱼类群落多样性低。梯级水电站的开发、过度捕捞以及外来种入侵对伊犁河鱼类鱼类群落造成了很大的影响。     

怒江流域鱼类多样性及空间分布格局

怒江是我国西南地区重要的国际河流, 也是全球生物多样性热点区域之一。受地理位置和地形条件限制, 目前尚缺乏怒江流域鱼类物种多样性及其分布格局的系统研究。本研究利用近5年的全流域实地采样数据, 结合文献资料, 系统整理了怒江流域鱼类物种组成信息; 利用聚类和排序方法分析了怒江流域鱼类空间分布格局。结果表明, 怒江流域共有土著鱼类85种, 隶属于5目12科47属; 外来鱼类18种, 隶属于3目8科16属, 另外实地调查发现新记录外来种2种。怒江流域鱼类多样性从上游至下游呈明显的递增趋势。根据土著鱼类组成的聚类和排序分析结果, 可以将怒江25个亚流域分为3个部分: (1)西藏自治区内的上游河段, 分布有鱼类15种, 组成以裂腹鱼类、高原鳅类为主, 具有明显青藏高原冷水性鱼类区系特征。(2)贡山至泸水的中游河段, 分布有鱼类36种, 组成兼有上游冷水性鱼类和下游喜温的鲃亚科、野鲮亚科鱼类。(3)泸水以下的下游河段, 分布有鱼类74种。下游河段干流广泛分布有喜温的鲃亚科、野鲮亚科和 亚科鱼类, 支流则分布有数量众多的南鳅属(Schistura)、纹胸鮡属(Glyptothorax)鱼类, 鱼类组成以适应流水、激流环境的热带亚热带鱼类为主。2017-2021年的多次调查仅发现土著鱼类43种(占历史记录的50.6%), 土著鱼类资源衰退明显。过度捕捞、支流小水电开发、外来鱼类入侵等是主要威胁因素。随着人类活动的急剧增多, 怒江流域鱼类将面临更大的威胁, 亟需从流域层面开展系统的鱼类资源管理和保护规划。     

赣南桃江和九曲河夏季大刺鳅资源现状评估

大刺鳅（Mastacembelus armatus）主要分布于我国南方各大水系,现阶段野生资源急剧减少,已被福建、广东、湖南等省列为重点保护野生水生动物。为了解赣南地区大刺鳅在主要分布水域桃江和九曲河中的资源状况,于2020年夏季对该水域鱼类和大刺鳅资源状况进行了调查,共采集鱼类34种隶属于4目11科31属。调查结果显示：所有样点本土鱼类中黄颡鱼（Pelteobagrus fulvidraco）、大刺鳅、鲫（Carassius auratus）为优势物种,桃江中外来物种莫桑比克罗非鱼（Oreochromis mossambicus）占主要优势;随着水利工程建设、外来物种入侵、栖息生境破坏及过度捕捞,大刺鳅资源量呈显著下降趋势。调查分析表明,修复自然河流生境,恢复洄游通道;增强本土物种保护意识,加强外来物种治理;严格禁捕,科学增殖放流对大刺鳅资源保护具有重要意义。     

海口五源河国家湿地公园鱼类群落结构及多样性研究

湿地是自然界生物多样性丰富、人类赖以生存和发展的环境之一，在生态系统中扮演着十分重要的角色。以往对湿地鱼类的研究一直相对匮乏，不利于进行湿地保护和湿地公园的开发和建设，本研究基于2021—2022年期间对海口市典型湿地——五源河湿地公园的鱼类群落调查数据，研究了该湿地公园鱼类群落结构及多样性。调查发现该湿地公园鱼类70种，隶属9目28科61属，其中纯淡水鱼类41种，河口鱼类29种；纯淡水鱼类中土著鱼类29种，外来鱼类12种；受威胁鱼类6种，海南特有种2种。湿地公园鱼类生态类型以杂食性、底层性、定居性鱼类为主；海南似鱎（Toxabramis houdemeri）、齐氏非鲫（Coptodon zillii）、须鲫（Carassioides acuminatus）、豹纹翼甲鲇（Pterygoplichthys pardalis）为该湿地公园的优势种；鱼类群落的Shannon-Weiner指数、Margalef指数、Pielou指数和Simpson指数平均值分别为2.11、5.19、0.59和0.26。结果表明，五源河湿地公园的鱼类多样性较高，但部分河段受到外来物种入侵和人为干扰的影响较大，亟需实施针对性的保护措施。     

云南澜沧江下游3种条鳅科鱼类中国新记录

澜沧江-湄公河作为一条国际河流,是全世界鱼类物种多样性最高的流域之一,其中中国境内澜沧江流域的条鳅科鱼类共记录37种,由于该类群分类鉴定较为困难,流域内仍存在未被发现、描述或准确鉴定的物种。2015至2019年,通过对云南省普洱市和西双版纳傣族自治州境内的澜沧江流域进行多次鱼类生物多样性调查,共发现3种未曾记录的条鳅科鱼类。对所采集到鱼类标本的重要性状进行测量,并与国内外相关文献进行形态特征比较,分别鉴定为长带条鳅（Nemacheilus longistriatus）、裸背南鳅（Schistura nudidorsum）和宽齿南鳅（S. latidens）,均为中国物种新记录;其中,由于以前在中国记录的条鳅属鱼类均已移入南鳅属（Schistura）,长带条鳅是目前中国分布的唯一条鳅属物种。本文对这3种新记录的条鳅科鱼类进行描述,对今后澜沧江条鳅科鱼类物种鉴定具有一定的指导意义,同时为澜沧江鱼类资源的调查和保护提供科学依据。     

西藏拉鲁湿地和茶巴朗湿地外来鱼类群落结构及变动趋势

研究于2019—2021年在西藏拉鲁湿地和茶巴朗湿地使用刺网和地笼等组合渔具开展了鱼类实地调查, 分析了外来鱼类物种组成、优势种和群落功能多样性, 并结合已发表的文献资料, 探讨了西藏湿地外来鱼类群落结构的变动趋势及影响。结果表明, 共采集到外来鱼类10种, 隶属于4目5科, 包括鲫(Carassius auratus)、麦穗鱼(Pseudorasbora parva)、鲤(Cyprinus carpio)、丁鱥(Tinca tinca)、棒花鱼(Abbottina rivularis)、泥鳅(Misgurnus anguillicaudatus)、大鳞副泥鳅(Paramisgurnus dabryanus)、鲇(Silurus asotus)、小黄?(Micropercops swinhonis)和中华青鳉(Oryzias sinensis)。外来鱼类的个体数和重量分别占本地种和外来种总渔获物的94.86%和70.71%, 其中主要组成为鲫和麦穗鱼等小型鱼类。相对重要性指数(IRI)表明鲫、麦穗鱼、大鳞副泥鳅和鲤4种为拉鲁湿地外来鱼类优势物种, 鲫、麦穗鱼和小黄?3种为茶巴朗湿地的优势物种。在拉鲁湿地和茶巴朗湿地鱼类种类组成、个体数量和生物量中外来鱼类均已占据优势地位, 且外来鱼类的群落功能多样性(FD)亦高于土著鱼类。结合历史数据, 西藏拉鲁湿地和茶巴朗湿地已记录外来鱼类12种, 其中具高度入侵风险物种达6种, 外来鱼类物种数从2000年左右的2种增加到现在的10种, 且丁鱥和中华青鳉分别在西藏自然水体中和茶巴朗湿地中首次被发现。此外, 两个湿地12种外来鱼类均为拉萨市场中的常见经济鱼类及携带鱼类, 是由于放生而进入湿地自然水体中, 且鲫、大鳞副泥鳅和麦穗鱼等均已建立自然种群。因此, 加强对放生的科学管理及开展外来鱼类的长期监测, 是防范外来鱼类入侵及高原湿地生物多样性保护的迫切任务。     

Alien Fishes in Natural Streams: Fish Distribution, Assemblage Structure, and Conservation in the Cosumnes River, California, U.S.A.

The Cosumnes River is the largest stream without a major dam on its mainstem in the Sacramento–San Joaquin drainage, central California, U.S.A. We studied its fishes over a 3-year period to answer the following questions: (1) Was the native fish fauna still present? (2) Why were alien fishes so abundant in a river system with a 'natural' flow regime, which elsewhere has been shown to favor native fishes? (3) Were there assemblages of fishes that reflected environmental differences created by the underlying geology? (4) Were there features of the watershed that consistently favored native fishes or that could be managed to favor native fishes? Of the 25 species collected, 17 were alien species; 14 species (five native) were abundant or widely distributed enough to use in detailed analyses. Of the native species, only rainbow trout, Oncorhynchus mykiss, still occupied much of its native range in headwater streams. Other native species have been extirpated or persisted mainly above barriers to alien invasions. The most widely distributed alien species was redeye bass, Micropterus coosae, previously unknown from the river, whose abundance was associated with low-numbers of native species. Other aliens were found primarily in low-land habitats on the valley floor or foothills. Canonical Correspondence Analysis indicated that both native and alien species located on environmental gradients determined largely by elevation, temperature, flow, and emergent vegetation, but the associations with these variables were not strong. While most alien fishes were found in lowland sections of river flowing through agricultural regions, the general relationships between species abundance and landscape-level variables were weak. Assemblages of fishes were poorly defined mixtures of native and alien species. The strikingly distinct geological regions of the basin no longer supported distinct fish assemblages. Species distributions were highly individualistic, reflecting dynamic patterns of introductions, invasions, and local extinctions, as well as physiological tolerances and life history patterns. Most native fishes are likely to persist in the Cosumnes River only if summer flows are increased and if populations above natural barriers are protected from further invasions by alien species, especially redeye bass. General conclusions from this study include: (1) altered habitats can support native species under some circumstances; (2) new fish assemblages with characteristics of 'natural' communities are likely to develop in invaded systems; (3) restoring flow regimes to favor native fishes may require restoring minimum summer flows as well as high channel-forming flows. However, reversing or even reducing, the impact of the predatory redeye bass, pre-adapted for California streams, is probably not possible.     

Spatial and temporal variation in assemblage structure of fish larvae in mediterranean–type streams: contrasts between native and non-native species

Larval fish ecology remains poorly understood in freshwater ecosystems. This study analysed the larval ecology of native and non-native fishes in a mediterranean-type watershed in Southern Iberian Peninsula. Assemblage structure of fish larvae was quantified at four distinct rivers sites, every 2 weeks between March and October 2004, and analysed against 16 variables reflecting river flow, temperature and habitat context. There was considerable spatial variation in taxonomic richness and abundance of larval assemblages, with either native or non-native fishes dominating in different sites. There was also a clear temporal separation between native and non-native fishes, with native cyprinids generally peaking earlier in the year than non-native fishes. Temporal fluctuations in larval assemblages across sites were mostly associated with variations in water temperature and transparency, but flow was an important factor shaping local assemblage structure. Larvae of native fishes appeared to found most suitable conditions in naturally flowing sites early in spring, when flow is high and water temperature stills low. These results suggest that preservation of natural flow peaks and adequate thermal contexts may be crucial for conservation of native fish fauna in mediterranean-type streams.     

Introductions of non-native fishes into a heavily modified river: rates,patterns and management issues in the Paranapanema River (Upper Paraná ecoregion,Brazil)

Understanding the pathways and impacts of non-native species is important for helping prevent new introductions and invasions. This is frequently challenging in regions where human activities continue to promote new introductions, such as in Brazil, where aquaculture and sport fishing are mainly dependent on non-native fishes. Here, the non-native fish diversity of the Paranapanema River basin of the Upper Paraná River ecoregion, Brazil, was quantified fully for the first time. This river has been subject to considerable alteration through hydroelectric dam construction and concomitant development of aquaculture and sport fishing. Through compilation of a non-native fish inventory by literature review, with complementary records from recent field studies, analyses were completed on the timings of introduction, and the taxonomy, origin and introduction vectors of the non-native fishes. A total of 47 non-native fishes are now present across the basin. Of these, 24 invaded from the Lower Paraná River following construction of Itaipu Dam that connected previously unconnected fish assemblages. Activities including fish stocking, aquaculture and sport angling continue to result in new introductions. Discounting Itaipu invasions, the introduction rate between 1950 and 2014 was approximately one new introduction every 3 years. Introduced fish were mainly of the Cichlidae and Characidae families; most species were from other South American ecoregions, but fishes of African, Asian, North American and Central American origin were also present. These introductions have substantially modified the river’s fish fauna; when coupled with altered lentic conditions caused by impoundment, this suggests that the river’s native fishes are increasingly threatened.     

The influence of habitat on the spatial variation in fish assemblage composition in an unimpacted tropical River of Ganga basin, India

Effects of local habitat variables on the structure of fish assemblage were evaluated from 50 sampling sites in a tropical River of Central India of the Ganges basin with limited anthropogenic disturbance covering premonsoon, monsoon and postmonsoon periods. Data were analyzed for 5,186 fish individuals of 24 freshwater fish species of conservation and fishery management interest. Out of the total fish species, seven belong to the ??endangered?? and 8 belong to the vulnerable category. A Cyprinid, Puntius sarana, was the most widely distributed species (frequency of occurrence 76%) out of the total species in this study. We used canonical correspondence analyses to determine the influence of environmental conditions on species occurrences and assemblage characteristics. Regarding the microhabitat, hydromorphological parameters (depth and current velocity) followed by temperature, turbidity and total dissolve solid were of significant for the structure of the fish community. Conductivity was another important factor that explained the major proportion of the variability affecting fish in their habitat choice. The other local habitat variables like overhanging vegetation and land use were of secondary but significantly important for the assemblage of the fishes. Our results suggests the importance of local environment influences on the fishes of conservation importance and their assemblage characteristics in an unimpacted river and provide a framework and reference conditions to support restoration efforts of relatively altered fish habitats in tropical rivers of India.     

基于环境DNA宏条形码的洱海鱼类多样性研究

研究使用环境DNA宏条形码(eDNA metabarcoding)检测洱海鱼类多样性, 探索适用于洱海鱼类多样性监测和保护的新方法。通过水样采集、过滤、eDNA提取、遗传标记扩增、测序与生物信息分析的环境DNA宏条形码标准化分析流程, 从洱海16个采样点中获得可检测的9个采样点数据, 共检测出17种鱼类, 其中土著种5种、外来种12种; 鲫(Carassius auratus)、鳙(Hypophthalmichthys nobilis)、麦穗鱼(Pseudorasbora parva)、泥鳅(Misgurnus anguillicaudatus)和食蚊鱼(Gambusia affinis)为优势种。研究结果表明虽然环境DNA宏条形码无法完全替代传统的鱼类监测方法, 但作为一种新兴的生物多样性监测手段, 其可用于快速检测洱海鱼类多样性及其空间分布。     

Asian aquarium fishes in a Neotropical biodiversity hotspot: impeding establishment, spread and impacts

We provide evidence of reproductive activities of nine Asian freshwater fish species belonging to three families in Atlantic Forest creeks located in the Paraíba do Sul River basin, southeastern Brazil, an area rich in endemic and endangered fish fauna. These non-native fishes were introduced into the natural systems by both accidental and intentional releases from ornamental fish farms in the region. Adults of all species were found reproducing during virtually all year round and showed fractionated spawning. Imature individuals (young-of-the-year and juveniles) were also frequent in the five sites. Most of the total sex ratios were close to 1:1. The frequent releases, warm water temperature, marginal vegetation providing food, protection and spawning sites, and the low richness of native fishes in these creeks can facilitate the establishment process of all species. The creeks can also act as dispersing agents of non-native fishes after flash floods, leading to biotic homogenization or differentiation in the local fish community, competition with native fishes, and parasite dissemination. Given the flourishing aquaculture activity in the area, it is expected that these and other non-native species cause extensive modifications in the regional ichthyofauna.     

Are amphipod invaders a threat to regional biodiversity?

The impact of invasions on local biodiversity is well established, but their impact on regional biodiversity has so far been only sketchily documented. To address this question, we studied the impact at various observation scales (ranging from the microhabitat to the whole catchment) of successive arrivals of non-native amphipods on the amphipod assemblage of the Loire River basin in France. Amphipod assemblages were studied at 225 sites covering the whole Loire catchment. Non-native species were dominant at all sites in the main channel of the Loire River, but native species were still present at most of the sites. We found that the invaders have failed to colonize most of tributaries of the Loire River. At the regional scale, we found that since the invaders first arrived 25 years ago, the global amphipod diversity has increased by 33% (from 8 to 12 species) due to the arrival of non-native species. We discuss the possibility that the lack of any loss of biodiversity may be directly linked to the presence of refuges at the microhabitat scale in the Loire channel and in the tributaries, which invasive species have been unable to colonize. The restoration of river quality could increase the number of refuges for native species, thus reducing the impact of invaders.     

Plagioscion squamosissimus (Sciaenidae) and Parachromis managuensis (Cichlidae): a threat to native fishes of the Doce River in Minas Gerais, Brazil

The middle section of the lake basin of the Doce River in Minas Gerais State, Brazil is plagued by grave environmental problems, including the introduction of non-native fish, which reduces the biodiversity of this region. This study reports the presence of two newly-detected non-native species in the Doce River Basin. Sampling efforts included gill nets with mesh size of 3 to 12 mm (measured diagonally) and trawling nets, both of which were used in independent field campaigns in 2002 and 2011. The two new invasive Perciform fishes, Plagioscion squamosissimus (Heckel 1840) and Parachromis managuensis (Günther 1867) were collected in Caratinga and Rio Doce municipalities. These records and other reports on non-native fishes suggest favorable environmental conditions for the establishment of invasive species in this drainage. These invasive species have behavior and diet observed in other wide distribution exotic fish of Rio Doce Basin representing a threat to the 77 native fishes of this region, 37 of which are endangered.