Impacts of Alien Invasive Species on Freshwater Fauna at Risk in Canada

Freshwater aquatic organisms in North America are disproportionately imperilled when compared to their terrestrial counterparts due to widespread habitat alteration, pollution, overexploitation and the introduction of alien species. In this review, we examine the threat factors contributing to the endangerment of freshwater fishes and molluscs in Canada and further examine the nature of alien invasive species introductions affecting aquatic species at risk. Habitat loss and degradation is the predominant threat factor for Canadian freshwater fishes and molluscs that are listed as Extinct, Extirpated, Endangered and Threatened. Alien invasive species are the second most prevalent threat for fishes, affecting 26 of 41 listed species. Alien invasive species are a threat in most parts of Canada where listed fishes are found. Most (65%) of the alien invasive species affecting listed fishes are the result of intentional introductions related to sport fishing, and the majority of these introductions are unauthorized. Fifteen fishes and two plant species are cited as alien invasive species that impact listed fishes with brown bullhead (Ameiurus nebulosus) and pumpkinseed (Lepomis gibbosus) being the most prevalent. Alien species are a threat to 6 of 11 listed mollusc species. All six species are threatened by the alien zebra mussel (Dreissena polymorpha) in the Great Lakes basin. An erratum to this article is available at .     

Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea)

Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world''s 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.     

Conservation threats and future prospects for the freshwater fishes of Ecuador: A hotspot of Neotropical fish diversity

Freshwater fish communities in Ecuador exhibit some of the highest levels of diversity and endemism in the Neotropics. Unfortunately, aquatic ecosystems in the country are under serious threat and conditions are deteriorating. In 2018–19, the government of Ecuador sponsored a series of workshops to examine the conservation status of Ecuador's freshwater fishes. Concerns were identified for 35 species, most of which are native to the Amazon region, and overfishing of Amazonian pimelodid catfishes emerged as a major issue. However, much of the information needed to make decisions across fish groups and regions was not available, hindering the process and highlighting the need for a review of the conservation threats to Ecuador's freshwater fishes. Here, we review how the physical alteration of rivers, deforestation, wetland and floodplain degradation, agricultural and urban water pollution, mining, oil extraction, dams, overfishing, introduced species and climate change are affecting freshwater fishes in Ecuador. Although many of these factors affect fishes throughout the Neotropics, the lack of data on Ecuadorian fish communities is staggering and highlights the urgent need for more research. We also make recommendations, including the need for proper enforcement of existing environmental laws, restoration of degraded aquatic ecosystems, establishment of a national monitoring system for freshwater ecosystems, investment in research to fill gaps in knowledge, and encouragement of public engagement in citizen science and conservation efforts. Freshwater fishes are an important component of the cultural and biological legacy of the Ecuadorian people. Conserving them for future generations is critical.     

Freshwater fish biodiversity in the River Ganga (India): changing pattern, threats and conservation perspectives

The river Ganges is the largest river in India and the fifth longest in the world. Although, many studies on fish ecology and systematic have been conducted largely to improve fisheries but fish diversity and their distribution pattern from conservation point of view have never been adequately addressed in the Ganges. In this connection, current distribution and abundance of freshwater fishes of river Ganges was studied and assessed from April 2007 to March 2009. We documented and described 143 freshwater fish species in the all stretches of the river which is higher than what was reported earlier. Some species were observed with shift in their distribution ranges. First time, a total of 10 exotic fishes, including Pterygoplichthys anisitsi, which has never been reported from India found in the Ganges. Alterations of the hydrological pattern due to various types of hydro projects was seems to be the largest threat to fishes of Ganges. Indiscriminate and illegal fishing, pollution, water abstraction, siltation and invasion of exotic species are also threatening the fish diversity in the Ganges and as many as 29 species are listed under threatened category. The study advocates a need to identify critical fish habitats in the Ganga basin to declare them as conservation reserves to mitigate the loss of fish diversity from this mighty large river.     

Evaluating functional diversity conservation for freshwater fishes resulting from terrestrial protected areas

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Assessing the conservation potential of fish and corals in aquariums globally

Aquatic ecosystems are indispensable for life on earth and yet despite their essential function and service roles, marine and freshwater biomes are facing unprecedented threats from both traditional and emerging anthropogenic stressors. The resultant species and ecosystem-level threat severity requires an urgent response from the conservation community. With their care facilities, veterinary and conservation breeding expertise, reintroduction and restoration, and public communication reach, stand-alone aquariums and zoos holding aquatic taxa have great collective potential to help address the current biodiversity crisis, which is now greater in freshwater than land habitats. However, uncertainty regarding the number of species kept in such facilities hinders assessment of their conservation value. Here we analyzed, standardized and shared data of zoological institution members of Species360, for fish and Anthozoa species (i.e. Actinopterygii, Elasmobranchii, Holocephali, Myxini, Sarcopterygii and Anthozoa). To assess the conservation potential of populations held in these institutions, we cross-referenced the Species360 records with the following conservation schemes: the Convention on the International Trade of Endangered Species of Fauna and Flora (CITES), the IUCN Red List of Threatened species, climate change vulnerability, Evolutionary Distinct and Globally Endangered (EDGE) and The Alliance for Zero Extinction (AZE). We found that aquariums hold four of the six fish species listed by the IUCN Red List as ‘Extinct in the Wild’, 31% of Anthozoa species listed by Foden et al. (2013) as vulnerable to climate change, 19 out of the 111 Anthozoa EDGE species, and none of the species prioritized by the AZE. However, it is very likely that significant additional species of high conservation value are held in aquariums that do not manage their records in standardized, sharable platforms such as Species360. Our study highlights both the great value of aquarium and zoo collections for addressing the aquatic biodiversity crisis, as well as the importance that they maintain comprehensive, standardised, globally-shared taxonomic data.     

Host-parasite interactions in oligotrophic stream ecosystems: the roles of life-history strategy and ecological niche

Biodiversity in fluvial ecosystems is under pressure as a consequence of their degradation. Conservation strategies for endangered freshwater molluscs and for salmonid fishes have been proposed but they are typically poorly integrated. Here, we examined for the first time the genetic structure of a critically endangered obligate mollusc invertebrate parasite, the freshwater pearl mussel ( Margaritifera margaritifera ), and its vertebrate host fish, the brown trout ( Salmo trutta m. fario ), in European headwater streams. We compared genetic differentiation and diversity with productivity and ecological habitat features of both species in nine different European streams from the drainage systems of the Danube, Elbe, Weser, Tuuloma, Kemijoki and Aulne. Genetic differentiation was more pronounced in pearl mussel than in brown trout, although the drainage-specific patterns were generally similar. Genetic diversity of host and parasite was negatively correlated. The most oligotrophic, postglacially colonized areas represented genetic diversity hotspots with high conservation priority for pearl mussels, whereas their host fish displayed low diversity in these areas. This pattern can be explained by differences in the ecological niches and in the life-history strategies of both species. These results question the effectiveness of single-species approaches in the conservation of genetic aquatic resources and suggest that genetic information from species with different life-history strategies, such as invertebrates and fish, should be considered simultaneously for geographical conservation prioritization in stream ecosystems.     

Restricted-Range Fishes and the Conservation of Brazilian Freshwaters

Background

Freshwaters are the most threatened ecosystems on earth. Although recent assessments provide data on global priority regions for freshwater conservation, local scale priorities remain unknown. Refining the scale of global biodiversity assessments (both at terrestrial and freshwater realms) and translating these into conservation priorities on the ground remains a major challenge to biodiversity science, and depends directly on species occurrence data of high taxonomic and geographic resolution. Brazil harbors the richest freshwater ichthyofauna in the world, but knowledge on endemic areas and conservation in Brazilian rivers is still scarce.

Methodology/Principal Findings

Using data on environmental threats and revised species distribution data we detect and delineate 540 small watershed areas harboring 819 restricted-range fishes in Brazil. Many of these areas are already highly threatened, as 159 (29%) watersheds have lost more than 70% of their original vegetation cover, and only 141 (26%) show significant overlap with formally protected areas or indigenous lands. We detected 220 (40%) critical watersheds overlapping hydroelectric dams or showing both poor formal protection and widespread habitat loss; these sites harbor 344 endemic fish species that may face extinction if no conservation action is in place in the near future.

Conclusions/Significance

We provide the first analysis of site-scale conservation priorities in the richest freshwater ecosystems of the globe. Our results corroborate the hypothesis that freshwater biodiversity has been neglected in former conservation assessments. The study provides a simple and straightforward method for detecting freshwater priority areas based on endemism and threat, and represents a starting point for integrating freshwater and terrestrial conservation in representative and biogeographically consistent site-scale conservation strategies, that may be scaled-up following naturally linked drainage systems. Proper management (e. g. forestry code enforcement, landscape planning) and conservation (e. g. formal protection) of the 540 watersheds detected herein will be decisive in avoiding species extinction in the richest aquatic ecosystems on the planet.     

Assessing the potential of a protected area for fish conservation in a neotropical wetland

Freshwater habitats are among the most impacted ecosystem on Earth. Consequently, reserves have been implemented in an attempt to reduce the threat to freshwater biodiversity. However, few studies have evaluated how effective these protected areas (PA) are for the conservation of freshwater organisms. In the present study, we compared species richness, community composition and density of small-bodied fishes between lagoons within an eight-year-old reserve (i.e. protected lagoons) with those outside the reserve (i.e. unprotected lagoons) in a river-floodplain system that is exposed to seasonal flooding. The unprotected lagoons have been submitted to a light fishing pressure mainly targeting small-sized fishes for sale as baits. Our results showed no differences between the lagoons inside the reserve with those outside in any of the community properties measured. However, we registered an overall tendency of abundance reduction among the species used as baits in unprotected lagoons. Considering the high degree of oversight in the PA and the low fishing pressure among unprotected lagoons, it is possible that the positive effects promoted by the reserve on fish assemblages are being exported towards unprotected lagoons and thus offsetting a portion of the anthropogenic impacts. We conclude that the protection provided by the reserve is very efficient in river-floodplain systems, because not only it protects the biota inside the reserve but also act as a source of propagules to unprotected areas during the rainy season when all the aquatic subsystems are connected by the flood.     

Impact of terrestrial protected areas on the fish diversity and habitat quality: Evidence from tropical river Pranhita,India

The conservation and management of inland fish and freshwater ecosystems immensely contribute to global sustainable development. The existing ‘Protected Area’ (PA) network does not represent freshwater resources well and seldom considers its fish communities, while designating PAs. A study was undertaken to quantitatively assess the role played by the three terrestrial PAs (IUCN category IV) in conserving fish diversity and preserving habitat quality in the river reaches bordering the three PAs of the river Pranhita. It is a unique river system in the Indian Deccan Plateau in terms of fish diversity and community structure. Field surveys were conducted during the non-monsoon and monsoon seasons in 2020–21, that recorded 53 species including endemic and threatened fishes from river Pranhita, which represent more than one-third the number of fish species of Telangana state. The higher diversity and lower dominance index value (p < 0.01) reported in PAs compared to Eco Sensitive Zones and unprotected areas during the non-monsoon season indicate the role of intact physical habitat in providing refuges to the fish species in monsoon dependent tropical rivers. The optimal water quality revealed no significant difference (p > 0.0001) between protected and unprotected river reaches, and healthy biotic integrity assessed on the basis of fish community structure was attributed to the contiguous flow and less anthropogenic disturbance. This study supports that it can be considered as a representative zone for the conservation and protection of indigenous and endemic fish species of the Godavari Basin. The results concluded that the scope of the terrestrial PA network in India could be potentially extended to their bordering aquatic ecosystems, especially rivers to maintain pristine habitat conditions and conserve the fish genetic resources to ensure the flow of ecosystem services.     

海南岛淡水蟹类分布格局与多样性保护

热带岛屿生物多样性是全球生物多样性保护研究的热点之一。海南岛是中国面积最大的热带岛屿, 丰富独特的淡水蟹类是维持岛内淡水生态系统功能完整性的关键类群。本文通过多年野外调查, 综合历史及最新文献资料, 对海南岛淡水蟹类物种多样性及其现状进行调查和评估, 并对淡水蟹类物种多样性保护现状进行了分析讨论。研究发现, 海南岛淡水蟹类物种多样性分布中心位于中南部山地, 主要集中于中部的霸王岭、鹦哥岭和猕猴岭, 南部的五指山和吊罗山, 以及西南部的尖峰岭一带。其物种多样性整体上呈现中南部山地高、平原台地低的特点。根据《IUCN物种红色名录濒危等级和标准》对海南岛淡水蟹类物种现状的评估结果显示, 全岛受威胁淡水蟹类物种的占比为16.7%。基于分布区预测, 以海南热带雨林国家公园为主体的保护地对淡水蟹类潜在适宜分布区的覆盖度明显优于此前碎片化的各级保护区。本文研究结果显示, 海南岛淡水蟹类的总体生存状况良好, 但一部分山地或平原种类处于受胁状态。国家公园体制的建立有望为岛内淡水蟹类物种多样性保护提供前所未有的机遇。基于物种多样性分布格局开展淡水蟹类等淡水生物多样性监测, 有助于促进海南岛淡水生态系统完整性的长效保护与可持续发展。     

黄河流域淡水鱼类多样性和保护

本文介绍了黄河流域鱼类研究的历史、淡水鱼类的物种组成、整体分布格局、特有性、濒危性, 以及鱼类多样性在黄河上、中、下游等的特点。历史上对于黄河鱼类多样性的研究, 历经了四个阶段, 从最初的零星记录一直到现阶段的深入研究。综合历史记录和野外调查, 已知黄河流域分布的淡水鱼类共计147种, 隶属于12目21科78属, 其中鲤形目种类占据绝对优势。另外, 全流域黄河特有种计有27种, 受危物种24种, 分别占总数的18.37%和16.32%。同中国主要江河相比, 黄河鱼类在高级分类阶元上的多样性较高, 但物种多样性则处在较低水平; 尽管黄河特有鱼类和受危物种比例低于全国平均水平, 但上游特有鱼类和珍稀濒危鱼类的占比很高。目前黄河鱼类多样性大幅降低, 现状调查仅能采获历史记录种类的53.06%。梯级水电开发、水资源过度利用、外来物种、水域污染和过度捕捞都是威胁鱼类多样性的重要因素, 但对各河段和支流的影响不一, 应做出有针对性的保护部署。     

基于环境DNA宏条形码技术的北京地区鱼类多样性调查和外来鱼种入侵风险评估

[目的]调查北京地区鱼类多样性和群落分布及评估外来鱼种的入侵风险.[方法]选取北京地区水库、湖泊和河流3种水体类型共33个采样点,于2020年6月10—17日开展水生态监测,利用环境DNA宏条形码技术对各样点的鱼类多样性和群落结构进行监测和分析,对目前北京地区水生态系统中本地鱼种和外来鱼种进行分类汇总,并评估典型外来入...     

淡水鱼类功能多样性及其研究方法

目前,群落功能多样性备受生态学界关注,被认为是能解决生态问题的一种重要途径。我国对于群落功能多样性主要集中在植物群落和微生物群落,而在鱼类群落方面的研究几乎是空白。我国鱼类资源正面临着严重威胁,包括水坝建设导致的鱼类通道受阻、水库形成造成鱼类产卵场功能消失、过度捕捞、水质恶化和富营养化加重、外来种入侵等因素,导致渔业资源急剧衰退,水生生态系统功能下降。以淡水鱼类群落为例,对鱼类功能多样性的数据获取及处理分析与评价、测定指标及计算方法与研究难点等进行综述,以期为鱼类资源保护提供新的理论依据和切入点。     

Paradigm shifts in fish conservation: moving to the ecosystem services concept

Various factors constrain the existence and development of inland fishes and fisheries, such as pollution, habitat degradation, alien invasive species, local user conflicts, low social priority and inadequate research and funding. In many cases, however, degradation of the environment and loss of aquatic habitat are the predominant concerns for the conservation of freshwater aquatic biota. The need for concerted effort to prevent and reduce environmental degradation, as well as protection of freshwater fishes and fisheries as renewable common pool resources or entities in their own right, are the greatest challenges facing the conservation of fishes in inland waters. Unfortunately, traditional conservation practices such as regulation of exploitation, protected areas and habitat restoration have failed to arrest the alarming increase in number of threatened freshwater fish species worldwide. This paper examines the shifting paradigm of fisheries management from rule-based regulation, through fishery enhancement towards the ecosystem approach to fisheries, with reference to inland waters, and how the emerging concept of ecosystem services coupled with traditional fish conservation management practices, institutional restructuring and integrated management planning should provide a more sustainable thrust to formulation and promotion of fish conservation initiatives.     

通过红色名录评估研究中国内陆鱼类受威胁现状及其成因

根据已有的基础资料, 采用IUCN评估等级和标准, 对中国目前已鉴定的1,443种内陆鱼类受威胁现状进行了评估。评估结果显示, 1,443种内陆鱼类中, 灭绝3种、区域灭绝1种、极危65种、濒危101种、易危129种、近危101种、无危454种和数据缺乏589种。同已有的IUCN评估结果相比, 本次被评估的物种数目多, 受威胁物种大幅度增加, 其数目达295种, 占已知中国内陆鱼类总数的20.44%, 低于全球平均值(29%)。属于灭绝等级的鱼类是大鳞白鱼(Anabarilius macrolepis)、异龙鲤(Cyprinus yilongensis)和茶卡高原鳅(Triplophysa cakaensis); 属于区域灭绝等级的鱼类是长颌北鲑(Stenodus nelma)。鲤科是受威胁物种数最多的科, 其中裂腹鱼亚科和鲤亚科的种类受威胁程度最高。长江上游和珠江上游受威胁物种最多, 是受威胁最严重的地区。中国内陆鱼类受威胁的主要因素为河流筑坝、生境退化或丧失、酷渔滥捕和引进外来种。列入数据缺乏等级的鱼类较多, 占中国内陆鱼类的40.82%, 表明对中国内陆鱼类物种多样性了解不充分, 需要加强野外调查以积累基础资料。     

康定市鱼类多样性野外调查与评估全文替换

2017年春季和夏季调查了康定市大渡河和立曲河水系鱼类多样性及分布,采用Margalef丰富度指数、Shannon-Wiener多样性指数、Pielou’s均匀度指数评估康定市鱼类多样性状况及主要威胁因素。调查结果表明,康定市域内共分布鱼类45种(亚种),隶属于3目8科22属,其中8种为外来种,37种为自然分布的土著鱼类。组成上以鲤形目Cypriniformes鲤科Cyprinidae的裂腹鱼亚科Schizothoracinae和条鳅科Nemacheilidae为主,占土著鱼类总物种数的78.37%。珍稀濒危鱼类共14种,川陕哲罗鲑Hucho bleekeri是国家一级重点保护野生鱼类。中国特有种25种。为加强康定市鱼类多样性保护与管理,建议加强流域层面的鱼类本底调查,建立重点物种栖息地保护区域,加强保护宣传,规范放生等。     

淡水鱼类功能生态学研究进展

在全球变化和人类活动的影响下,生物多样性正以前所未有的速度丧失,全球生物正经受第六次生物多样性危机。淡水生态系统是最脆弱的生态系统之一。淡水鱼类作为淡水生态系统的重要组成部分,承受着日趋严重的气候变化、栖息地退化、生物入侵和过度捕捞等压力,面临巨大的威胁。在此背景下,如何准确评估鱼类种群和群落对环境变化的响应,以及鱼类群落结构和功能的变化对生态系统功能的影响是淡水鱼类多样性和淡水生态系统保护的关键问题。近年来,淡水鱼类功能生态学的快速发展为解答这一问题提供了一个框架。系统地介绍了淡水鱼类功能生态学主要研究内容、方法、进展及其应用,并着重介绍了淡水鱼类功能特征及其与环境的关系、环境变化下的功能生态学响应研究。据此提出了淡水鱼类功能生态学未来的重点研究方向,指出了其在鱼类多样性保护和资源利用等领域的应用前景。     

The Great Lakes in East Africa: biological conservation considerations for species flocks

The three largest water bodies of East Africa, Lake Victoria, Tanganyika, and Malawi contain an estimated number of 2,000 endemic cichlid fish species, in addition, to a mostly uncounted wealth of invertebrates. While the terrestrial diversity is reasonably well protected, as economic and touristic interests coincide with biological conservation strategies, this is not the case for most African lakes and rivers. Nonetheless, it must be promoted that these aquatic ecosystems also deserve protection. Conservation strategies for aquatic biota have so far been the same as for terrestrial environments, i.e., by declaring biodiversity hotspots national parks. Such parks also contain rivers and lake shores. Here, I argue that it seems questionable that this strategy will work, given strong micro-geographic structure of the species flocks and the great degree of local endemism. I suggest a novel strategy for protecting African Lake communities that accounts for local endemism, derived from recent molecular phylogenetic and phylogeographic studies on East African cichlid fishes. While connectivity is the major problem for terrestrial and marine national parks, to ensure a large enough effective population size of the protected animals, this is not the case in most taxa of African rivers and lakes, where local endemism prevails. For example, most littoral cichlid species are subdivided into numerous distinct “color morphs” with restricted distribution, and unlike marine fishes with planktonic larvae display brood care with small offspring numbers. It is argued that the establishment of “micro-scale protected areas,” a large number of small stretches of strictly protected coast line, each only some hundreds of meters long, is likely to work best to preserve the littoral communities in African lakes. Such protected zones can sustain a reasonably effective population size of littoral species, serve as protected spawning ground or nursery area for pelagic species, and at the same time re-seed neighboring populations that are exploited continuously. As long-term stability of littoral fishing grounds is in the immediate interest of village communities, such small protected areas should be managed and controlled by the local communities themselves, and supervised by governmental institutions.     

Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence‐absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm‐water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.