“For example, we ought to be able to save the Baltic cod if we fished herring and sprat. Likewise, the salmon trout in depleted lakes could be revived if we culled the char, which is what the salmon trout preys on,” says Lennart Persson, professor of aquatic ecology at Umeå University. The latter is precisely what has been done in a 26-year experiment in Lake Takvatn in Norway.
Thanks to this experiment and a mathematic model, Lennart Persson and his collaborative partners at the universities of Amsterdam and Tromsö have been able to show that it is actually possible to favor predators by fishing their prey.
The more prey, the more predators, says a time-worn ecological theory. However, this is not necessarily true. When there are few prey, the remaining prey grow more rapidly. This, in turn, can lead to more sexually mature individuals, which leads to more small prey, which the predator fish prefer. Paradoxically, a predator fish can therefore increase the amount of small prey fish by eating them. If there aren’t enough predatory fish, owing to increased harvesting, for instance, the reverse situation ensues. The number of prey that the predators live on will decline.
“We will then see a downward spiral leading to the collapse of the predator stock. Since the growth of the prey fish is impaired, it can become impossible for the predatory fish to recover if we introduce a total embargo on fishing. Instead, we should harvest the prey fish in order to bring about more individual prey of the size the predators feed on,” explains Lennart Persson.
In this way the predatory fish stock can recover and thereafter improve their own situation by eating their prey.
By harvesting char in the lake in Norway, Lennart Persson and his colleagues have managed to increase the number of small char individuals that predator fish prefer. The number of salmon trout, in turn, has burgeoned. Before restocking started, the salmon trout had largely disappeared from the lake; the char were not growing properly, and there was too little food for the salmon trout. The restocking was completed 16 years ago, and since then the salmon trout have been able to maintain the entire ecosystem of the lake in a state with rapidly growing char and thereby plenty of prey for the trout.
Both the model prediction and the large-scale lake experiment indicate that harvesting prey fish can be an effective way to restore collapsed stocks of predatory fish. The article is titled “Culling prey promotes predator recovery-alternative states in a whole lake experiment” and is published this week in the journal Science, see http://sciencemag.org.
The findings are based on collaboration with researchers at Tromsö University and Amsterdam University.
Lennart Persson | alfa
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology