“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
Listening in: Acoustic monitoring devices detect illegal hunting and logging
14.12.2017 | Gesellschaft für Ökologie e.V.
How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences