Browsing All Posts filed under »predation«

Mosquitofish threaten frogs

September 25, 2017

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The mosquitofish, Gambusia holbrooki, is one of the most invasive freshwater fish species in the world.  Although it’s been widely introduced for mosquito control, it has a broad diet that includes algae, higher plants, detritus, invertebrates and fish.  As a result, the species has negative predatory and competitive effects on native fish.   Although declines in […]

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 […]

Coarse, shallow and wooden… but useful nonetheless

June 19, 2017

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Coarse woody debris (CWD) derived from shoreline trees provides an important, spatially complex habitat and a food source for lake-dwelling organisms. Here are some interesting facts about lake CWD, taken from a recent review paper: In the absence of the physical action of flowing water, CWD breaks down more slowly in lakes than in streams. […]

Plankton migration is system-dependent

June 19, 2017

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Lake zooplankton commonly switch microhabitats on a regular day-night basis by migrating horizontally between stands of vegetation and open waters, or by migrating vertically between deep and surface waters. These movements have been explained in terms of the need to avoid predators (especially fish) and excessive ultraviolet radiation.  However, although zooplankton are known to seek […]

How big is a food patch?

June 19, 2017

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Most studies of food patch choice by foraging animals have assumed that the patches in question are separate and well-defined. However, in many cases, predators feed in continuous habitats without obvious, discrete patches, and researchers are forced to choose an arbitrary spatial scale when calculating prey densities and interpreting the impacts of predators. An important […]

Top predator boosts species richness – but not in alien ecosystems

December 13, 2016

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The spiny water flea Bythotrephes longimanus is a large cladoceran, a specialised carnivore and a top predator. Invasions of North American lakes by Bythotrephes have been linked to dramatic changes in food web structure and reductions in species diversity, which seems to contradict the expectation that top predators increase the evenness and diversity of aquatic […]

Restoration ecology: are we forgetting top-down control?

June 1, 2016

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Authors of a recent review article argue that restoration ecologists rely heavily on the assumption that natural communities are controlled by bottom-up processes (i.e., the upward transfer of nutrients and energy from plants to animals), but tend to ignore the complementary effects of top-down control by animals on nutrient cycling and the abundance and diversity […]