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- The European Water Framework Directive 2000/60/EC (WFD) defines the ecological status of aquatic systems as the deviation between their present biological state and that which would be expected in the absence of any major human disturbance, referred to by the WFD as the ‘reference condition’ (RC). It assumes that their biotic composition should remain balanced and constant over time. This study tested both assumptions against an analysis of the historical distribution of the fish fauna in a large and highly disturbed Mediterranean basin. If fish communities change substantially over time, it will mean that the validity of the RC concept comes into question.
- Using presence/absence data for historical native fish fauna from the Guadalquivir Basin, distribution changes among sub-basins were quantified by mapping between the nineteenth century and today.
- The range of two native species (Anguilla anguilla and Salmo trutta) has changed significantly. In addition, the diadromous species assemblage has almost become locally extinct, with the exception of the eel. Finally, most Guadalquivir sub-basins (94.7%) have suffered major changes in the composition of their fish communities, either by losing native species or by adding new non-native species.
- These results render the definition of any RC unlikely. In Mediterranean areas, the WFD objective of ‘good ecological status’ recovery based on the integrity of aquatic communities is a theoretical rather than a real goal. Nonetheless, the WFD provides an ecological guiding principle that can also be transferred to the conservation of freshwater ecosystems.
- As an alternative to the RC concept in Mediterranean lotic ecosystems, specific multimetric indices can be used, based on expert criteria, the metrics of which can also relate to the conservation value of water bodies, and not only to their ecological status.
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- 1. Tropical, high islands of the Pacific have developed unique freshwater fish faunas that are currently threatened by a range of human activities. This paper documents distinct differences in life history strategies from fish communities found in streams of Fiji compared with fish assemblages in freshwater systems on larger continental land masses. While river systems of northern Australia and Papua New Guinea have a high proportion of freshwater residents, the Fiji fauna is dominated by amphidromous gobiids that migrate across a broad range of habitats throughout their life cycle.
- 2. The number of amphidromous fish species and the number of all fish species in mid‐reaches of Fiji rivers are significantly affected by loss of catchment forest cover and introductions of tilapia (Oreochromis spp.). On average, stream networks with established Oreochromis spp. populations have 11 fewer species of native fish than do intact systems. The fish that disappear are mostly eleotrid and gobiid taxa, which have important dietary and economic value.
- 3. Based on the strong links between catchment land clearing, non‐native species introductions and loss of migratory pathways for freshwater fish, spatial information was compiled on a national scale to identify priority areas for conservation in Fiji with intact connectivity between forests, hydrologic networks and coral reefs. Areas with high connectivity included remote, largely undeveloped regions of Vanua Levu (Kubulau, Wainunu, Dama, Udu Point, Natewa, Qelewara) and Taveuni, as well as smaller mapping units (Naikorokoro, Sawakasa) of Viti Levu with low density of roads and high relative amounts of mangroves and reefs.
- 4. These priority areas for conservation can only be effectively protected and managed through cross‐sectoral collaboration and ecosystem‐based approaches. Copyright © 2009 John Wiley & Sons, Ltd.
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Lydia X. Gan Claudia L. Y. Tan Amirrudin B. Ahmad Yixiong Cai Darren C. J. Yeo 《水产资源保护:海洋与淡水生态系统》2023,33(1):89-101
- Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.
- Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.
- This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.
- Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.
- These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.
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Ana Rita Dias Amílcar Teixeira Manuel Lopes‐Lima Simone Varandas Ronaldo Sousa 《水产资源保护:海洋与淡水生态系统》2020,30(5):988-999
- Coextinction is the simplest form of secondary extinction and freshwater mussels (Bivalvia, Unionida) may be particularly prone to this phenomenon as their life cycle includes an obligatory parasitic larval stage on fish hosts.
- The main aims of this study were to determine the possible ecological fish hosts of Anodonta anatina (Linnaeus, 1758) in several rivers of the Douro basin in northern Portugal and to assess possible spatial and temporal differences in glochidial (larval) loads. In order to achieve this, electrofishing was conducted from December to April, the fish fauna was characterized, and levels of infestation with A. anatina glochidia were determined.
- Native cyprinid species, mainly Luciobarbus bocagei (Iberian barbel) and Squalius carolitertii (northern Iberian chub), together with the non‐native Lepomis gibbosus (pumpkinseed sunfish) and Alburnus alburnus (common bleak), were found to have the highest glochidial loads. Clear differences in infestation between rivers and throughout time were detected, with an infestation period from January to March, and with the Tâmega River having the highest prevalence.
- Anodonta anatina is able to infest a variety of fish species, and this together with earlier studies showed that the metamorphosis into juveniles occurs mainly in native cyprinid species, although non‐native species like common bleak can also be considered suitable hosts. However, the larvae infesting other non‐native species, such as the pumpkinseed sunfish, do not metamorphose and can be considered ‘dead ends’.
- Overall, the results reported here are important for the conservation of A. anatina (and other unionoid species) because several Iberian rivers (and worldwide) have been subjected to the extirpation of native fish species and the introduction of non‐native fish species. Therefore, careful assessments of fish communities should be conducted to assess possible negative interactions with freshwater mussels.
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Comparative genomic insights into the taxonomy of Edwardsiella tarda isolated from different hosts: Marine,freshwater and migratory fish 
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下载免费PDF全文 Edwardsiella tarda, a Gram‐negative member of the family Enterobacteriaceae, has been isolated from many animal species worldwide, especially fish species. Its broad host range indicates the diversity in taxonomy, which attracted the attention of many researchers. Here, we added genome of E. tarda strain isolated from freshwater fish to comparative genomics study for the first time. We sequenced and assembled the genome of E. tarda ASE201307 which was isolated from freshwater Asian swamp eel. ASE201307 genome contained a single circular chromosome of 3.68M with G+C 57.09% content. Comparative genomics including SNP calling, synteny block, Core/Pan genes analysis and phylogeny analysis was conducted among ASE201307 and other Edwardsiella strains isolated from different fish species. Results of SNP analysis and synteny block demonstrated the close relative of ASE201307, FL95.01 and DT which were all isolated from freshwater fish. In further analysis heat map of dispensable genes and phylogenetic tree, all E. tarda strains were divided into two groups. One was isolated from freshwater fish and the other was isolated from marine/migratory fish. Based on all studies above, we proposed the living environment of hosts as a new taxonomic character and divided E. tarda isolated from diseased fish into freshwater group and marine/migratory group. 相似文献
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- 1. Studies dealing with the fish fauna of coastal streams are scarce in the scientific literature, particularly those from Mediterranean climates. Owing to their small size, these systems suffer extreme seasonal fluctuations, following the typical Mediterranean flood–drought cycle and leading to a high risk of extinction to freshwater fish.
- 2. This work analyses fish distribution in 14 stream stretches belonging to eight basins in the northern sector of the Strait of Gibraltar (southern Spain). Fish–habitat relationships were studied through multivariate ordination techniques at two scales: basin and stretch.
- 3. A principal components analysis clearly discriminated larger and more sinuous basins from smaller and steeper ones. This ordination was related to the non‐migratory freshwater fish species richness and to the total number of fish species present in the middle reaches of each basin.
- 4. The main sources of variation in community composition and habitat characteristics in the different stretches were related to a clear upstream–downstream gradient, along which total species richness increased.
- 5. These small coastal basins are inhabited by two highly endangered species, Andalusian toothcarp (Aphanius baeticus) and Iberian chub (Squalius pyrenaicus), and have similar or higher overall freshwater species richness than larger adjacent basins. The near absences of flow regulation and introduced species make these streams one of the few types of Iberian aquatic system where unaltered fish–habitat relationships can be studied.
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Renata G. Frederico Murilo S. Dias Céline Jézéquel Pablo A. Tedesco Bernard Hugueny Jansen Zuanon Gislene Torrente-Vilara Hernan Ortega Max Hidalgo Koen Martens Javier Maldonado-Ocampo Thierry Oberdorff 《水产资源保护:海洋与淡水生态系统》2021,31(12):1158-1166
- The Amazon basin has been subjected to extreme climatic events and according to climate change projections this hydrosystem could face changes in the natural dynamic of flood cycles that support the feeding and reproduction of many fish species, threatening aquatic biodiversity.
- Protected areas (PAs) are the main tools used to safeguard the biodiversity in the long term; however, they are fixed areas that could be subject to climate change, questioning their future efficiency in protecting biodiversity.
- The Amazon basin currently benefits from a relatively high level of protection as 52% of its catchment area is under the form of true PAs or indigenous lands. However, the capacity of these PAs to protect freshwater biodiversity remains unclear as they have generally been assessed with little regard to freshwater ecosystems and their hydrological connectivity. Here, the aim was to evaluate the effectiveness of PAs in representing the Amazon fish fauna under current and future climatic conditions.
- A macroecological approach was used to estimate the minimum size of the geographical range needed by each species to achieve long-term persistence, by a combined function of range size and body size, two ecological traits known to influence species extinction risk.
- In future the Amazon basin could risk losing 2% of its freshwater fish fauna owing to unsuitable climatic conditions, with a further 34% adversely affected. The present Amazon network of PAs will cover the minimum required range for species persistence for more than 60% of the freshwater fish species analysed under the future climate scenario. However, more than 25% of the future susceptible species are currently concentrated in large tributaries and in the central-lower Amazon floodplain where few PAs occur, highlighting the lack of appropriate conservation actions for these specific water bodies.
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- 1. A basin approximation was used to analyse distribution patterns of different components of biodiversity (taxonomic richness, endemicity, taxonomic singularity, rarity) and conservation status of freshwater fish fauna in 27 Mediterranean Iberian rivers.
- 2. Basin area alone explained more than 80% of variation in native species richness. Larger basins featured not only a higher number of native species, but also more endemic and rare species and fewer diversified genera than smaller basins.
- 3. In contrast, smaller basins scored higher community conservation values, owing to their lower degree of invasion by introduced species.
- 4. The presence of dams was the most important factor determining the conservation status of fish communities, and it was also positively associated with the number of introduced species.
- 5. While the most important components of Iberian freshwater fish biodiversity are located in large basins, small unregulated basins feature better conserved fish communities.
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Status of galaxiid fishes in Tasmania,Australia: conservation listings,threats and management issues
Scott A. Hardie Jean E. Jackson Leon A. Barmuta Robert W.G. White 《水产资源保护:海洋与淡水生态系统》2006,16(3):235-250
- 1. Fish of the family Galaxiidae are restricted to the southern hemisphere where they occupy a diverse array of habitats ranging from over 2000 m in elevation to sea level. Some species are diadromous and, hence, freshwater, estuarine and marine habitats are used during their life‐cycle; other species complete their entire life‐cycles in freshwater environments.
- 2. Tasmania has a diverse galaxiid fauna that accounts for 64% of native freshwater fish species found on the island. The Tasmanian galaxiid fauna is characterized by high species richness (5 genera and 16 species), endemism (11 species), restricted distributions, and non‐diadromous life histories (11 species).
- 3. The galaxiid fauna of Tasmania has significant conservation status with 69% of species considered ‘threatened’. The conservation status of the fauna is recognized at State, national and international levels.
- 4. The key threats to galaxiids in Tasmania are exotic species, hydrological manipulations, restricted distributions, general habitat degradation and exploitation of stocks.
- 5. Although work has recently been undertaken to conserve and manage Tasmanian galaxiid populations, the fauna is still thought to be imperilled. Knowledge gaps that need to be addressed include the biology and ecology of most species (e.g. reproductive biology, life histories, habitat use and requirements) and impacts of habitat manipulations, as well as mechanisms and impacts of interactions with exotic species. Techniques to monitor accurately the status of galaxiid species and their populations need to be developed and the coexistence of some galaxiids with introduced salmonids should also be examined.
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L. J. Chapman 《Ecology of Freshwater Fish》1995,4(3):113-123
I examined the effects of extreme hypoxia and water level fluctuations on the distribution and movement of an air-breathing clariid catfish, Clarias liocephalus, in a papyrus swamp in western Uganda. Monthly records of the distribution and relative abundance of C. liocephalus across 28 swamp stations were used to examine seasonal trends in habitat use and movement. My results suggest that dissolved oxygen did not directly limit use of, or dispersal through, the papyrus swamp. C. liocephalus were found at most stations in the dry season, and there was no significant relationship between the number of stations used per month and mean monthly dissolved oxygen levels. In addition, there was no evidence for a significant effect of oxygen on the relative abundance of fish among stations during the driest months, or during peak flood conditions. However, relative abundance was positively correlated with water depth during the dry season. Fish from deeper habitats exhibited fewer injuries and lower rates of disappearance than fish from shallower waters. This may reflect the risk of aerial predation for surfacing fish. A comparison of habitat use and movements of C. liocephalus with the only other fish species found in the papyrus swamp, Barbus neumayeri, supports the idea that respiratory mode can affect the use of hypoxic papyrus swamps. B. neumayeri, is a small water-breathing cyprinid that uses aquatic surface respiration in response to severe hypoxia. The air-breathing capabilities of C. liocephalus permitted more widespread use of swamp waters than B. neumayeri. This study demonstrates that an understanding of the respiratory mode of fish species may be useful in predicting patterns of habitat use. 相似文献
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Current status of parasitic ciliates Chilodonella spp. (Phyllopharyngea: Chilodonellidae) in freshwater fish aquaculture 下载免费PDF全文
下载免费PDF全文 《Journal of fish diseases》2017,40(5):703-715
Freshwater fish farming contributes to more than two‐thirds of global aquaculture production. Parasitic ciliates are one of the largest causes of production loss in freshwater farmed fishes, with species from the genus Chilodonella being particularly problematic. While Chilodonella spp. include ‘free‐living’ fauna, some species are involved in mortality events of fish, particularly in high‐density aquaculture. Indeed, chilodonellosis causes major productivity losses in over 16 species of farmed freshwater fishes in more than 14 countries. Traditionally, Chilodonella species are identified based on morphological features; however, the genus comprises yet uncharacterized cryptic species, which indicates the necessity for molecular diagnostic methods. This review synthesizes current knowledge on the biology, ecology and geographic distribution of harmful Chilodonella spp. and examines pathological signs, diagnostic methods and treatments. Recent advances in molecular diagnostics and the ability to culture Chilodonella spp. in vitro will enable the development of preventative management practices and sustained freshwater fish aquaculture production. 相似文献
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Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion,northern Australia 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 Angela H. Arthington Paul C. Godfrey Richard G. Pearson Fazlul Karim Jim Wallace 《水产资源保护:海洋与淡水生态系统》2015,25(3):336-352
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- 1. Arizona's native fish species are among the most imperilled fauna in North America. Knowing the current distribution of native fish and their habitat is critical to their management and conservation, but the last detailed mapping effort was more than 30 years ago and pre‐dated computer mapping techniques.
- 2. Current distribution of 34 native fish species was modelled by identifying perennial stream segments for which species presence had been documented. A composite of these single‐species maps displays a pattern of species richness that can inform conservation, especially when overlaid with maps of management status or invasive species.
- 3. The map overlays suggest that conservation priorities should include Eagle Creek, the Verde River and its tributaries, Aravaipa Canyon, the Virgin River and Black Draw, which together hold 63% of native fish species. Of the 32 streams that support five or more native species, 28 have at least one non‐native fish species, indicating that a more aggressive programme of removing non‐natives may be critical to maintaining those native populations.
- 4. The U.S. Forest Service and Native American tribes administer the majority of occupied stream habitat (30% and 27%, respectively). While private lands hold the third‐highest amount of occupied habitat (19%), they control streams occupied by the greatest total number of native species (30). Conservationists should work more with private land owners, while also coordinating efforts with the U.S. Forest Service and North American tribes.
- 5. These data are publicly available (on the Internet, URL: www.azconservation.org ) to encourage refinement and use.