Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion,northern Australia

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Spatial patterns of lacustrine fish assemblages in a catchment of the Mississippi Alluvial Valley

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Managing threats and restoring wetlands within catchments of the Great Barrier Reef,Australia

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Assessing the relative impacts of land‐use change and river regulation on Burdekin River (Australia) floodplain wetlands

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Approaches to the selection of a network of freshwater ecosystems within New Zealand for conservation

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The representativeness of protected areas for Amazonian fish diversity under climate change

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

     

Salinity tolerance during early development of threatened Murray hardyhead (Craterocephalus fluviatilis) to guide environmental watering

1. The worldwide reduction in wetlands has led to the large‐scale decline of wetland‐dependent species. In Australia, to redress some of the decline, partial restoration of the hydrology of a small number of wetlands has been attempted using allocations of environmental water.
2. A common goal of the watering is the maintenance and enhancement of native fish communities, which historically have included populations of the salt tolerant Murray hardyhead (Craterocephalus fluviatilis), a small, short‐lived fish, endemic to the lower Murray–Darling Basin.
3. Despite the addition of environmental water to several sites at which the species is known to persist, populations continue to decline. This decline is, at least in part, suspected to be a consequence of salinities that conflict with the breeding ecology and survival of early life stages.
4. Here the effect of salinity on egg hatch rate and the upper salinity tolerance of larval and juvenile Murray hardyhead was determined under laboratory conditions. It was found that eggs were vulnerable to elevated salinities, whereas juveniles were capable of tolerating salinities up to 105 ppt.
5. Based on the results of the experiment, brackish wetlands managed for Murray hardyhead should be maintained, where possible, between 12 and 45 ppt. Such a salinity regime will necessitate less intensive management of salinity, and a reduced volume of environmental water, providing both environmental and fiscal benefits. The research highlights the benefits of investment in targeted research.

     

Managed and natural inundation: benefits for conservation of native fish in a semi‐arid wetland system

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Amazon floodplain hydrology and implications for aquatic conservation

1. The amplitude, duration, frequency, and predictability of runoff and inundation of aquatic habitats are key hydrological characteristics linked to aquatic ecosystem functioning and biodiversity, but they are seldom integrated into analyses of Amazon floodplain ecology. Remote sensing approaches, measurements and modelling of floodplain hydrology provide a basis for this integration.
2. Effective legislation to protect floodplains and other wetlands depends on operational definitions that require application of hydrological data.
3. Extent and changes of flooded areas are linked to fish diversity and to presence and growth of flooded forests and floating plants.
4. Dam construction reduces river system connectivity and modifies the flood pulse, with major negative implications for floodplain ecosystems adapted to and dependent on a natural flood regime.
5. Trends and variability in climate plus deforestation are altering the Amazon's hydrological cycle, causing changes in discharge and flooded area with concomitant ecological impacts.

     

Connectivity between lentic and lotic freshwater habitats identified as a conservation priority for coho salmon

1. Juvenile Pacific salmon exhibit diverse habitat use and migration strategies to navigate high environmental variability and predation risk during freshwater residency. Increasingly, urbanization and climate-driven hydrological alterations are affecting the availability and quality of aquatic habitats in salmon catchments. Thus, conservation of freshwater habitat integrity has emerged as an important challenge in supporting salmon life-history diversity as a buffer against continuing ecosystem changes.
2. To inform catchment management for salmon, information on the distribution and movement dynamics of juvenile fish throughout the annual seasonal cycle is needed. A number of studies have assessed the ecology of juvenile coho salmon (Oncorhynchus kisutch) during summer and autumn seasons; catchment use by this species throughout the annual cycle is less well characterized, particularly in high-latitude systems.
3. Here, n = 3,792 tagged juvenile coho salmon were tracked throughout two complete annual cycles to assess basin-wide distribution and movement behaviour of this species in a subarctic, ice-bearing catchment.
4. Juvenile coho salmon in the Big Lake basin, Alaska, exhibited multiple habitat use and movement strategies across seasons; however, summer rearing in lotic mainstem environments followed by migration to lentic overwinter habitats was identified as a prominent behaviour, with two-thirds of tracked fish migrating en masse to concentrate in a small subset of upper catchment lakes for the winter. In contrast, the most significant tributary overwintering site (8% of tracked fish) occurred below a culvert and dam, blocking juvenile fish passage to a headwater lake, indicating that these fish may have been restricted from reaching preferred lentic overwinter habitats.
5. These findings emphasize the importance of maintaining aquatic connectivity to lentic habitats as a conservation priority for coho salmon during freshwater residency.

     

Identifying priority areas for surface water protection in data scarce regions: An integrated spatial analysis for Zambia

1. This study aimed to develop an integrated analytical framework to identify candidate sites for surface water protection that is applicable at broad scales and in data scarce regions, using Zambia as a case study.
2. In the Zambian Water Resources Management Act of 2011, Water Resource Protection Areas are defined as areas where special measures are necessary for the protection of a catchment, sub-catchment, aquifer, or geographical area. Three specific selection criteria are listed for the definition of Water Resource Protection Areas: (i) areas of high importance in providing water to users in a catchment; (ii) aquatic areas of high ecological importance; and (iii) areas that are particularly sensitive to human impact.
3. In this project, each sub-catchment and river reach of Zambia was characterized for their importance regarding these three criteria. ‘Water provisioning’ was assessed by analysing patterns of runoff generation and human water use; ‘aquatic ecological importance’ was determined by conducting a freshwater biodiversity and ecosystem assessment using a systematic conservation planning approach; and ‘sensitive areas’ were identified by quantifying erosion potential and sediment transport. The work was supported by an assessment of free-flowing rivers in Zambia, i.e., those rivers where aquatic ecosystem functions and services are largely unaffected by changes to fluvial connectivity through dams and other infrastructure.
4. Highly ranked sub-catchments were found in the Liuwa, Barotse, and Bangweulu floodplains and wetlands, and in the headwater regions of the upper Zambezi, Kafue, Chambeshi/Luapula, and Tanganyika catchments. The Luangwa was identified as the highest ranked candidate river for protection within Zambia.
5. The resulting maps, data, and methods are intended to support national-scale efforts to prioritize areas for surface water protection, identify catchments and rivers with high conservation value, optimize decision making for infrastructure development, and inform concerted strategies to maintain and restore freshwater ecosystem services in Zambia.

     

Land use surrounding wetlands influences urban populations of a freshwater turtle

1. Urbanization is one of the most influential land use changes globally and continues to affect wetland ecosystems and their biota. Freshwater turtles, which rely on both terrestrial and aquatic habitats to complete their life cycles, are one of the most endangered vertebrate groups, with approximately 60% of species threatened. Although habitat alteration caused by urbanization is recognized as one of the main threats to freshwater turtles, there is a paucity of studies quantifying the effects of terrestrial habitat change on turtle populations.
2. The aim of this study was to determine how terrestrial land use change, associated with urbanization, influences the viability of freshwater turtle populations. Thirty‐three wetlands were sampled for the southwestern snake‐necked turtle (Chelodina colliei Gray, 1856) (Chelidae) between October 2016 and February 2017 within a region of continuing urban intensification. Land use and habitat types were classified at the aquatic–terrestrial interface and within a 300‐m band around each wetland. Generalized linear mixed models were used to identify the land use variables that best explained the relative abundance of C. colliei.
3. Turtle abundance and population structure varied widely among wetlands. The percentage of residential land use, and the presence and accessibility of fringing native vegetation, was positively associated with the relative abundance of C. colliei. The association with residential land use may be an artefact of historical land use, whereas the association with native vegetation is probably because adjacent vegetation provides connectivity with suitable nesting sites, and thus facilitates increased recruitment.
4. This study shows how the modification of terrestrial habitat around wetlands may directly influence the population viability of freshwater turtles. Protection and restoration of native vegetation fringing urban wetlands is crucial to support the viability of remnant freshwater turtle populations.

     

Local and regional macroinvertebrate diversity in the wetlands of a cleared agricultural landscape in south‐western Victoria,Australia

• 1. Seasonal pasture wetlands are a common freshwater habitat in many agricultural landscapes, but their invertebrate diversity has rarely been examined compared with other freshwater habitats. Few studies have examined the role of seasonal wetlands for regional biodiversity or the pattern of change in assemblage composition across landscapes.
• 2. Invertebrates were sampled from 16 naturally occurring seasonal wetlands and three perennial wetlands in south‐western Victoria, Australia. The wetlands were arranged in three clusters, separated by at least 20 km: two clusters each contained one perennial and four seasonal wetlands surrounded by pasture; the remaining cluster consisted of one perennial wetland and four seasonal wetlands on a property that has not been cleared of native vegetation, and four adjacent seasonal pasture wetlands cleared of native vegetation.
• 3. Presence/absence data showed that seasonal wetlands had fewer taxa than perennial wetlands, but both were taxon rich. Turnover of taxa was high at all three scales, i.e. between samples within a wetland, between wetlands, and between wetland clusters, but each cluster did not have a characteristic assemblage composition. Up to two‐thirds of the invertebrate taxa found in perennial wetlands were also found in seasonal wetlands, showing that seasonal pasture wetlands could provide an expanded area of winter–spring habitat for many taxa.
• 4. Seasonal pasture wetlands contribute to biodiversity in highly managed and depauperate agricultural landscapes. There was little regionalization of the fauna, taxon turnover was high and ranges appeared relatively continuous. Biodiversity in pasture wetlands was comparable to perennial non‐pasture wetlands elsewhere, despite being used for grazing livestock. This suggests that pasture wetlands may have substantial conservation value and should be managed to protect them from threatening processes such as drainage.

Copyright © 2005 John Wiley & Sons, Ltd.     

Spatial distribution patterns of fish egg and larval assemblages in the lower reach of the Yangtze River: Potential implications for conservation and management

1. River fish diversity is threatened by anthropogenic environmental alteration to landscapes. The early life-history stages of fish play an important role in maintaining diversity and population recruitment and can be heavily influenced by landscape patterns. Information on temporal and spatial distribution patterns of fish eggs and larvae is also important for biodiversity conservation and management of fish resources.
2. The Yangtze River possesses a high diversity of fishes, including many commercially important species. The economy along the lower reach of the river is well developed, and most of the area is experiencing high pressure from human impacts. This section of the Yangtze River connects with the largest freshwater lake in China at the upstream end and flows into the estuary at the downstream end. These two landscape features are likely to have a significant impact upon the spatial distributions of fish egg and larval assemblages.
3. Environmental variables, fish eggs, and larval assemblages were sampled in three locations, at Hukou, Anqing, and Jingjiang, in the lower reach of the Yangtze River. The results suggest that the higher number of species and greater abundance in upstream sites reflect the critical function of connectivity of Poyang Lake with the river for fish recruitment in the lower Yangtze. The delayed bloom of larval fish, occurrence of estuarine species, and a lower species number and abundance of freshwater fish downstream reflect the influence of tidal intrusion from the estuary.
4. This study highlights the value of maintaining natural river–lakes connectivity in the Yangtze River as a conservation measure. The connected river–lake system should be designated as a priority area for fish resource protection in the lower reach of the Yangtze River. We recommend further measures to break down barriers between the river and other lakes and to restore the natural lateral connectivity of the floodplain ecosystem.

     

Is current floodplain management a cause for concern for fish and bird conservation in Bangladesh's largest wetland?

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Desktop classification of inland wetlands for systematic conservation planning in data‐scarce countries: mapping wetland ecosystem types,disturbance indices and threatened species associations at country‐wide scale

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Connectivity,habitat, and flow regime influence fish assemblage structure: Implications for environmental water management in a perennial river of the wet–dry tropics of northern Australia

1. Environmental water management seeks to balance competing demands between the water needed to sustain human populations and their economic activities and that required to sustain functioning freshwater ecosystems and the species they support. It must be predicated on an understanding of the environmental, hydrological, and biological factors that determine the distribution and abundance of aquatic species.
2. The Daly River of the wet–dry tropics of northern Australia consists of a perennially flowing main stem and large tributaries, as well as many small to large naturally intermittent tributaries, and associated off‐channel wetlands. Increased groundwater abstraction to support irrigated agriculture during the dry season threatens to reduce dry‐season flows that maintain perenniality and persistence of freshwater fishes.
3. Fish assemblages were surveyed at 55 locations during the dry season over a 2‐year period with the goal of establishing the key landscape‐scale and local‐scale (i.e. habitat) drivers of fish species distribution.
4. Longitudinal (upstream/downstream) and lateral (river/floodplain) gradients in assemblage structure were observed with the latter dependent on the position in the river landscape. Underlying these gradients, stream flow intermittency influenced assemblage composition, species richness, and body size distributions. Natural constraints to dispersal were identified and their influence on assemblage structure was also dependent on position within the catchment.
5. Eight distinct assemblage types were identified, defined by differences in the abundance of species within five groups differing in functional traits describing body size, spawning requirements, and dispersal capacity. These functional groups largely comprised species widely distributed in northern Australia.
6. The results of the study are discussed with reference to the environmental flow needs of the Daly River and other rivers of northern Australia. The findings may also be applied to environmental flow management in savannah rivers elsewhere.

     

Fishing for conservation of freshwater tropical fishes in the Anthropocene

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The importance of ecosystem‐based management for conserving aquatic migratory pathways on tropical high islands: a case study from Fiji

• 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.