Modelling functional fish habitat connectivity in rivers: A case study for prioritizing restoration actions targeting brown trout

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Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low‐cost remote sensing

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Averting the baiji syndrome: conserving habitat for critically endangered dolphins in Eastern Taiwan Strait

• 1. Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo‐Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central‐western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past.
• 2. The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land.
• 3. They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals.
• 4. Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define ‘priority habitat’ and implement much needed protection measures under the terms of local legislation.
• 5. The preferred habitat of these dolphins in Taiwan consists of shallow (<30 m), near‐shore marine waters with regular freshwater inputs.
• 6. For such a small, isolated and threatened population, ‘priority habitat’ should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current ‘habitat’), as well as additional coastal areas with similar bio‐physical features (‘suitable habitat’). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population‐level consequences.
• 7. While conventional socio‐economic analysis might suggest that implementing protection measures over an area stretching ～350 km north–south along Taiwan's west coast and ～3 km out to sea would be too ‘costly’, the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability. Copyright © 2010 John Wiley & Sons, Ltd.

     

Influence of intertidal seascape on the functional structure of fish assemblages: Implications for habitat conservation in estuarine ecosystems

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Spatial differences across the French Pyrenees in the use of local habitat by the endangered semi‐aquatic Pyrenean desman (Galemys pyrenaicus)

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Defining critical habitat conditions for the conservation of three endemic and endangered cyprinids in a Mediterranean intermittent river before the onset of drought

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Influences of local habitat and stream spatial position on fish assemblages in a dammed watershed,the Qingyi Stream,China

Abstract – Identifying the underlying mechanisms that explain the spatial variation in stream fish assemblages is crucial for the protection of species diversity. The influences of local habitat and stream spatial position on fish assemblages were examined from first‐order through third‐order streams within a dammed watershed, the Qingyi Stream, China. Based on linear regression models, the most important environmental variables influencing fish species richness were water temperature and wetted width, but stream spatial position variables were less important. Using canonical correspondence analysis, five environmental variables were identified to significantly influence fish assemblages, including three habitats (elevation, substrate and water depth) and two spatial variables (C‐link and Link). Our results suggest that, in a heavily dammed watershed, by blocking the migration routes of fishes, dams weaken the influence of stream spatial position on fish species richness. However, fish species compositions are significantly influenced by both local habitat environment and stream spatial position, which is perhaps owing to the distribution of fish species according to ecological requirements not related to spatial processes.     

Quantifying the effect of semi‐natural riparian cover on stream temperatures: implications for salmonid habitat management

Previous studies examining the effects of riparian cover on stream temperatures have led to highly variable findings. In an attempt to reduce these uncertainties, this study examines the relationship between stream temperature variability and local climatic conditions over discrete 300‐m sections of a watercourse. Seventeen stream sections were chosen within the Slaney catchment on the basis of riparian cover and size. Continuous monitoring over a 2‐year period from May 2010 found that riparian cover had a measurable cooling effect on water temperatures at small spatial scales. The magnitude of this effect was dependent on stream size and local climactic conditions.     

Machine learning highlights the importance of primary and secondary production in determining habitat for marine fish and macroinvertebrates

1. Species distribution models for marine organisms are increasingly used for a range of applications, including spatial planning, conservation, and fisheries management. These models have been constructed using a variety of mathematical forms and drawing on both physical and biological independent variables; however, what might be called first-generation models have mainly followed the form of linear models, or smoothing splines, informed by data collected in the context of fish surveys.
2. The performance of different classes of variables were tested in a series of species occurrence models built with machine learning methods, specifically evaluating the potential contribution of lower trophic level data. Random forest models were fitted based on the classification of the absence/presence for fish and macroinvertebrates surveyed on the US Northeast Continental Shelf.
3. The potential variables included physical, primary production, secondary production, and terrain variables. For accepted model fits, six variable importance measures were computed, which collectively showed that physical and secondary production variables make the greatest contribution across all models. In contrast, terrain variables made the least contribution to these models.
4. Multivariable analyses that account for all performance measures reinforce the role of water depth and temperature in defining species presence and absence; however, chlorophyll concentration and some specific zooplankton taxa, such as Metridia lucens and Paracalanus parvus, also make important contributions with strong seasonal variations.
5. Our results suggest that lower trophic level variables, if available, are valuable in the creation of species distribution models for marine organisms.

     

Conservation of otter (Lutra lutra) in a Mediterranean area: the importance of habitat quality and temporal variation in water availability

1. This study analyses quantitatively the association between habitat characteristics and annual variation in water availability on otter (Lutra lutra L.) distribution in a large Mediterranean area (13 717 km²) in southern Spain. 2. There was a strong positive correlation between habitat quality, estimated after the two first components of a principal component analysis of a matrix of habitat variables×sites, and an index of otter presence/absence, otter presence being most commonly associated with unpolluted and undisturbed sites surrounded by woodland. 3. After univariate analysis, the main freshwater habitat features were statistically different between sites with otters and sites lacking them. In general, otters occurred in medium‐sized fluvial habitats, with high bankside vegetation cover, unpolluted, with low or very low human disturbance and surrounded by forests or dehesas (Mediterranean‐like savannah). 4. Water availability, inferred from the water balance, strongly influenced otter distribution and the type of water body used the most. As water availability increased so did the otter distribution range and during these periods they tended to colonize low‐order streams. During periods of water shortage, otters were usually found in high‐order streams and reservoirs, the only sites that kept water. 5. This work shows that otter distribution in Mediterranean areas is strongly influenced by two factors — man‐induced habitat degradation and natural variability in water availability. The addition of the second factor to the first one introduces additional risks to the survival of otter populations in Mediterranean areas compared with more northerly and humid areas. Copyright © 2001 John Wiley & Sons, Ltd.     

Objective classification of Navarro River salmon habitat: a watershed‐based critical habitat case study

• 1. Prevailing freshwater conservation approaches in the USA stem from policy‐based ecosystem management directives, science‐based gap analyses, and legal interpretations of critical habitats. In California, there has been no systematic prioritization of freshwater habitats critical to the persistence of anadromous salmonid populations.
• 2. Anadromous salmonids provide an optimal focal species for conservation prioritization of freshwater habitats in California owing to their flagship, umbrella and keystone status.
• 3. The Navarro River is a key watershed for both Endangered Species Act and Clean Water Act recovery efforts in the state of California. This watershed serves as a case study in the use of iterative discriminant analysis to objectively classify freshwater habitats critical to the persistence of two species of threatened anadromous salmonids, steelhead (Oncorhynchus mykiss) and coho (Oncorhynchus kisutch).
• 4. Riverscape parameters were used initially to define suitable habitat for focal species; subsequent refinement accounted for human disturbance within the watershed. Results from this study identify 22.1 km of riverine habitat critical to the persistence of coho salmon in the Navarro River watershed, which need active conservation or restoration; it also identified an additional 269.4 km of riverine habitat in need of protection for its aquatic habitat values.

Copyright © 2007 John Wiley & Sons, Ltd.     

Need for speed: Preference for fast‐flowing water by the endangered semi‐aquatic Pyrenean desman (Galemys pyrenaicus) in two contrasting streams

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Shining a light on the loss of rheophilic fish habitat in lowland rivers as a forgotten consequence of barriers,and its implications for management

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Effects of sedimentation on an endangered benthic fish,Cobitis shikokuensis: is sediment‐free habitat a requirement or a preference?

A negative correlation between the degree of fine sediment deposition and the abundance of stream benthic fishes has often been reported, although the causal mechanisms for this effect are not fully understood. To better understand the influence of sedimentation, it is important to clarify whether it alters the habitat required by fish, or merely preferred by them. We conducted two enclosure experiments in the field to examine (i) whether an endangered benthic fish, Cobitis shikokuensis, prefers sediment‐free substrate and (ii) whether fine sediment deposition has negative effects on the physiological condition of C. shikokuensis. The first experiment, which used three types of substrates, ‘cobble’, ‘pebble’ and ‘mixture of fine sediment and pebbles’, showed that C. shikokuensis avoided the mixture. The second experiment, which compared the physiological condition of fish reared in enclosures with either a pebble or mixture substrate, showed that the condition of the fish in the latter group declined more quickly. These results suggest that, for C. shikokuensis, sediment‐free substrate is a habitat requirement, not merely a preference, and that excessive input of fine sediment due to human activities can cause a decline in the population of this species.     

Preliminary study of the endangered populations of pearl mussel Margaritifera margaritifera (L.) in the River Tera (north‐west Spain): habitat analysis and management considerations

• 1. During 2001 and 2002, 12 tributaries of the River Duero basin, north‐west Spain, were sampled. Pearl mussels Margaritifera margaritifera (L.) were located in two of them. Isolated individuals were found in the River Tera, a tributary of the River Esla; and only a few colonies with more than 20 mussels were found in the River Negro.
• 2. All of the specimens found were adults (mean length 95 mm), with juveniles being absent in the river bed. The River Negro plots showed a low median mussel density (0.11 m^?2), and that of greatest size consisted of 164 ageing individuals.
• 3. Mussels were mainly located in permanent rivers and in shallow stretches with little flow of water, with heterogeneous substrates and heavily shaded by the riparian woods. The whole basin has well‐conserved rivers with cold oligotrophic water and poor mineralization due to the insolubility of the rocks.
• 4. This relic population has a severely restricted distribution because of a series of large reservoirs in a hydropower complex of the rivers Duero and Esla (caused by the construction of the Ricobayo Dam in 1947) and their negative impact on the rheophilous fish. The mussels of the River Tera have been isolated from the rest of the Duero basin since 1969 (Cernadilla Dam), whereas in the River Negro they have been isolated since 1995 (Agavanzal Dam).

Copyright © 2004 John Wiley & Sons, Ltd.     

Interactions of baseflow habitat constraints: Macroinvertebrate drift,stream temperature,and physical habitat for anadromous salmon in the Calapooia River,Oregon

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长江上游珍稀特有鱼类保护区鱼类生境特征初步研究

长江上游珍稀特有鱼类保护区是我国最长的河流型自然保护区,保护了多种珍稀特有鱼类,具有重大的生物多样性保护价值。随着金沙江梯级开发的实施,长江上游保护区鱼类栖息条件将受到不同程度的影响。本研究基于长江上游珍稀特有鱼类保护区的地形、地貌、水文、水动力等条件,提出了保护区鱼类生境特征表征指标体系,并根据该指标体系初步分析了保护区栖息地生境特征。研究结果可为长江上游珍稀特有鱼类保护区鱼类资源保护措施的制定提供参考依据。     

Benthic habitat modelling and mapping as a conservation tool for marine protected areas: A seamount in the western Mediterranean

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Factors affecting habitat selection by a small spawning charr population, bull trout, Salvelinus confluentus: implications for recovery of an endangered species

Bull trout, Salvelinus confluentus (Suckley), populations are declining in many streams of North America and are listed under the Endangered Species Act in the United States. Many small populations are isolated in fragmented habitats where spawning conditions and success are not well understood. Factors affecting habitats selected for redds by spawning bull trout and redd habitat characteristics within Gold Creek, a headwater stream in the Yakima River within the Columbia River basin, Washington State, USA, were evaluated. Most spawning (>80% of the redds) occurred in upstream habitats after dewatering of downstream channels isolated fish. Habitats were selected or avoided in proportions different to their availability. For example, most bull trout selected pools and glides and avoided riffles despite the latter being more readily available. Although preferences suggest influences of prolonged fish entrapment, site fidelity could be important. A habitat with redds commonly contained abundant cover, gravel substratum and higher stream flows. The major factors influencing habitat selection by spawning fish and their persistence in streams of the Yakima and Columbia River regions include entrapment of fish by dewatering of channels and geographical isolation by dams. The goal of the US Government's recovery plan is ‘to ensure the long‐term persistence of self‐sustaining bull trout populations’. Recovery plans linked to provisions for protecting and conserving bull trout populations and their habitats were recommended. Landscape approaches are needed that provide networks of refuge habitats and greater connectivity between populations. Concurrent recovery efforts are encouraged to focus on protecting small populations and minimizing dangers of hybridization.     

Modelling stream fish species distribution in a river network: the relative effects of temperature versus physical factors

Abstract – The relative influence of temperature versus local physical factors on the spatial distribution of riverine fish species was investigated in a large watershed of south-western France. Using generalised additive models and hierarchical partitioning, we modelled the ecological responses of 28 fish species to a set of five environmental predictors, and we quantified the independent effect of each predictor. The spatial distribution of fish species was primarily determined by both mean temperature and position along the upstream–downstream gradient. However, responses to these environmental factors varied according to the species considered. Fish species with strong thermal requirements (e.g., common carp, black bullhead, Atlantic salmon) were mainly sensitive to temperature whereas longitudinal gradient was of primary importance for downstream species (e.g., common bream, largemouth bass, pike perch). Both the statistical methods used gave concordant results and appeared complementary. This dual-approach, quantifying the relative contribution of each environmental factor, appears particularly useful to understand the spatial distribution of stream fish species. Separating the effects of temperature versus habitat factors is crucial to accurately predict species distribution modifications in the current context of global change.