Browsing All Posts filed under »population«

Understanding how fish benefit from river restoration

January 14, 2019

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Although relationships between fish traits and environmental factors are well known, there have been few attempts to use fish traits to interpret the outcomes of stream restoration projects.  German scientists set out to do this by analyzing  data from a tributary of the Rhine River, which had a long history of channelization, bank fixation, riparian […]

Top-down control varies within a species

January 14, 2019

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  Because consumer species can impose strong top-down effects on the structure and functioning of aquatic ecosystems, the loss or replacement of apex species may lead to dramatic alterations to the food web.  But can different forms of the same consumer species be sufficiently distinct that the replacement of one form by another triggers a […]

Research on insect emergence warms up

October 8, 2018

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Long-term data show that climate change affects ecosystem functioning and the body size distributions of animal species, but more information is needed to understand the mechanisms underlying these changes.  There’s a need for experimental studies that take account of linkages between the aquatic and terrestrial environment and that simulate changes in the intensity and frequency […]

Lakes are good for river species

October 8, 2018

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While it’s known that terrestrial landscape features, such as soil type, topography and land use, influence the abundance and distribution of stream fish, only a few studies have considered the possible effects of lakes on stream fish populations.  Biologists carried out a three-year study on native brook trout (Salvelinus fontinalis) in 36 streams in the […]

Why are there so many crocodiles in tropical waterholes?

March 26, 2018

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Transfers of organic material from one aquatic environment to another (for example, through flood pulses or animal migrations) allow productive donor ecosystems to subsidise less productive habitats. However, there are big variations in the extent to which different animal species depend on production subsidies.  To explore such differences, Australian researchers collected a wide array of […]

Freshwater fish surveys: direct observation works well

March 26, 2018

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Although surveys of freshwater fish populations often rely on electrofishing, it’s difficult to use this technique in some habitats. An alternative sampling method is direct observation by snorkelling, an approach often applied in marine environments.  While comparisons of the sampling efficiency of electrofishing and snorkelling have been carried out, most of them have been based […]

Predatory fish control prey populations – but not when the prey are other fish

September 25, 2017

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Many lake studies have shown that predatory fish feeding on plankton or bottom-living invertebrates have a strong influence on the density, species composition and size structure of prey populations. Typically, there’s an inverse relationship between predator and prey populations, both in terms of  density and in mean body size.  However, there have been few reports […]