Browsing All Posts filed under »population«

Freshwater megafauna under threat

March 26, 2022

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Because large-bodied animal species tend to have a higher than average extinction risk, there are concerns that freshwater megafauna (species with body weights over 30 kg) are relatively vulnerable to human-induced disturbances such as reduced river flows, habitat fragmentation and pollution.  In the 40 years leading up to 2012, global populations of freshwater megafauna declined […]

Dams challenge platypus populations

March 26, 2022

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The construction of dams has many adverse effects on river hydrology and ecology.  Dams limit animal movements and reduce the cover of riparian vegetation, which leads to bank erosion and the filling of stream pools with sediment.  Dam-related impacts have been documented for many types of riverine animals, including macroinvertebrates, amphibians and waterbirds.  However, the […]

Gene flow in complex river systems

December 14, 2021

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Understanding how variations in habitat connectivity affect gene flow and possible genetic isolation in river systems is tricky because of the unique structural features of stream ecosystems, which are notoriously difficult to model: unlike terrestrial landscapes, they are linear branching networks, which means that overland distance is often a poor indicator of the correlation between […]

In-stream wood increases fish abundance

September 28, 2021

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Although fallen woody material provides many freshwater fish species with essential habitat for feeding, refuge and spawning, a lot of submerged wood has been removed from rivers in an attempt to prevent floods and improve boat passage. However, current best management practice is to reverse this historical trend by reintroducing wood to rivers and streams.  […]

A game changer: measuring biodiversity from water samples

June 7, 2021

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What are the processes and mechanisms that underpin biodiversity, and how is biodiversity related to ecosystem function?  There’s a need for answers to these questions with respect to all ecosystems, but it’s arguably most urgent for freshwater systems, which show the largest loss of biodiversity as a result of human pressures.  Ideally, to recognise the […]

Underwater cameras spot rare fish

March 13, 2021

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When species are rare they can remain undetected at a given site even when they’re actually there.  However,  occupancy modelling can be used to adjust for imperfect detection and assess whether a species is likely to be present.  Occupancy models allow for the effects of habitat variation on detection probability and they’ve been widely used […]

Linking population density to distribution

December 17, 2020

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The relationship between the abundance of a species and its occurrence across sites is important because it links ecological processes at different spatial scales.  For many types of animals and plants the relationship has been found to be positive, so that species that are highly abundant at a site also tend to occupy many sites.  […]

Ecosystem impacts of invasive carp

December 16, 2020

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The common carp (Cyprinus carpio) is one of the world’s most widespread invasive fish species and has a reputation for causing ecological damage.  It’s thought that the excretion of nutrients by dense populations of carp stimulates algal growth, which increases turbidity, and that the feeding and spawning activities of carp further increase turbidity by bringing […]

How birds use Amazonian lakes

June 25, 2020

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In the Amazon, most ecological studies have focussed on forest environments and data on freshwater biodiversity are relatively scant, even though vast areas of the catchment are flooded for several months each year.   In the largest ecological study of Amazonian waterbird communities to date, the dependence of birds on the physical and spatial features of […]

Coming to grips with community complexity

June 25, 2020

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Although it’s well known that the mix of species in natural communities is influenced by environmental factors and the geography of habitat patchiness, it’s unclear how these factors create the spatial and temporal patterns observed in nature.  Brazilian ecologists tested the hypothesis that the structure of freshwater plankton communities can be explained, at least in part, […]