Sometimes though, killing even a few individuals can have dramatic consequences, causing populations to fluctuate wildly. “The important question is: who gets killed" The effects of killing individuals crucially depend on the size of the victims,” says Tobias van Kooten, assistant professor at Umeå University in Sweden.
The regulation of populations is usually determined by the properties of one specific size class of individuals. In some species, this “crucial stage” consists of small individuals that can monopolize the available food, denying it to all other individuals.Alternatively, especially in fish populations, large individuals can limit the abundance of smaller individuals through cannibalism. It is when such a crucial size class is the target of mortality that unexpected things may happen.
Van Kooten and co-workers predict for example that in harvested cannibalistic fish populations, individuals may reach “giant” sizes, more than double the size of those in unharvested population. Indeed, such “giant cannibals” seem to occur frequently in heavily fished lakes. “Our results are directly applicable to conservation and management, since almost all human-induced mortality is size-selective,” van Kooten states. “Fishermen select gear to catch large fish, while deer hunters prefer the tender meat of calves.”
Unexpected effects of mortality have been reported before, but this systematic study, to be published in The American Naturalist, unravels the mechanisms behind the effects. Such “deep” understanding makes it possible to predict effects of size-dependent mortality for a wide range of species.
Patricia Morse | EurekAlert!
Species may appear deceptively resilient to climate change
24.11.2017 | University of California - Davis
Scientists team up on study to save endangered African penguins
16.11.2017 | Florida Atlantic University
High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons
The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
24.11.2017 | Physics and Astronomy
24.11.2017 | Health and Medicine
24.11.2017 | Earth Sciences