Browsing All Posts filed under »population dynamics«

A lesson from fish: don’t let stress ruin procreation

March 26, 2022

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Annual fishes live in temporary ponds that dry out completely in summer.  As a result they have the shortest life spans of all vertebrates: after a few months they perish and the next generation depends on the survival of their drought-proof eggs, which hatch when the pond is eventually flooded.  As the shallow ponds dry […]

Aquatic insects on the decline

September 28, 2021

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Although there’s growing evidence that species in many animal groups, including insects, amphibians, aquatic invertebrates and birds, are experiencing dramatic and widespread declines in abundance, identifying the factors driving these changes is a major challenge because most ecosystems are affected by several stressors at the same time.  In addition, long-term data sets on species abundance […]

How rivers regulate fish numbers

June 7, 2021

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Recruitment processes, which determine the number of young animals entering a  population each year, are central considerations in our attempts to understand fluctuations in abundance.  Although recruitment has been a key focus of fisheries scientists for many years, most of their work has involved marine fish species, and there’s been no fully integrated and comprehensive […]

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 […]

Climate change: weighing up the pluses and minuses

March 31, 2020

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Because the vulnerability of a species to climate change can vary with life stage, there’s a need to consider the challenges and opportunities presented by climate warming across the whole lifetime.  This is particularly important in the case of species with complex life cycles, or where juveniles and adults of the same species inhabit different […]

Invasive species counter evolutionary responses to fishing

September 23, 2019

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Harvesting by humans can have far-reaching effects on the population structure of exploited species and the dynamics of food webs – for example, fishing often removes the largest and oldest individuals in a population disproportionately, which selects for animals that grow faster and mature earlier.  Harvesting may also interact with changes in environmental conditions, but […]

Fish life histories: filling in the gaps

July 5, 2018

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Estimates of life history parameters such as age at maturity, maximum body size and rates of growth and mortality play a crucial role in understanding and managing animal populations, but in the case of many species they’re lacking or poorly measured.  Fortunately however, compilations of existing estimates now exist, and these databases open up opportunities […]

Human impacts on ecological connectivity

June 19, 2017

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Ecological connectivity – the exchange of organisms between habitat patches or subpopulations – has an influence on many key processes, including population dynamics, nutrient flux, disease transmission, species invasions, food-web interactions, genetic isolation and the maintenance of biodiversity. A recent study reviewed ways in which graph theory has been used to investigate how human activities […]

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 […]

Remote surveillance:monitoring fish populations

June 1, 2016

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Submerged vegetation provides freshwater animals with food, substrate and refuge opportunities. Although the structural complexity of aquatic vegetation can make it difficult for researchers to study the behaviour of resident species and measure the size of their populations, the advent of high-resolution, low-light video systems promises to alleviate these problems. Working in Florida, researchers carried […]