How fishing could change the evolution of fish

SOme Fish are more Probably the others to be captured. Imagine a fisherman throwing their line in a lake, a lure hanging in the water: this can go unnoticed by a pike which is naturally shy. But other pikes are risk takers and are more likely to venture, despite the risk of being engulfed by predators. Usually, it is the daring fish that finds the bait and is dragged out of the water.

Until recently, many scientists did not appreciate these dynamics and thought of the consequences of fishing mainly in terms of abundance of fish. Research is young, but it is clear that killing 1.6 billion of wild fish each year – the estimated toll of global peaches – for which also subtle and long -term consequences on the mind and bodies of animals because fishing does not affect fish within a population in an equally but target certain individuals. He often selectively picks up large fish in the nets or attracts fish with special behaviors. This, in turn, could have an impact on fishing as well as whole aquatic ecosystems. Potentially, “you could have repercussions for the entire operation of the food network,” explains evolutionary physiologist Amélie Crexel from the University of Turku in Finland. Indeed, fishing can gradually change the composition of the remaining population. In many generations, he could even influence the evolution of fish.

“If you have to die young, then you live quickly.”

For example, if shy behavior is supported by certain genes, and only these genes are transmitted to offspring, a whole population over time would evolve to become shy. But the most striking of these changes involves size. Researchers have long noticed that many species under intense fishing pressure have become smaller In recent decades. For some species, like the Atlantic codIt is probably because the fillets of chalts selectively pick up large old fish. Some scientists also suspect an evolutionary effect in which intensively caught populations are evolving to become smaller or mature faster, explains the evolutionary biologist Beatriz Pauli at the Norwegian Directorate of Fisheries.

Prove that fish evolve is delicate, especially in nature, because it requires long -term follow -up of animal genes. But the experiments show that the fishing targets in a disproportionate way individuals with certain features, which can change the composition of the remaining population in an ecologically significant – and long -term way could lead to an evolutionary change. In a still abundant study carried out while Pauli was at the University of Bergen, she and her colleagues have raised hundreds of tiny guppies and simulated the effect of selective size. In a set of tanks, they withdrew a quarter of Guppys greater than 16 millimeters; In other tanks, they followed the same calendar, but only chose smaller guppys or selected them at random without regard for size. Over time, the male fish exposed to the scenario similar to a trawling began to mature much earlier. Women, on the other hand, have produced offspring at younger ages.

Although Pauli has no genetic evidence that the fish has really changed these changes, it issued that the experience of a trawling building has essentially forced fish to develop a growth strategy that suralimates their maturation, thus increasing their chances of reproducing before being captured. “If you have to die young, then you live quickly, right? This is what fishing does,” said Pauli. Curiously, these faster fish also behaved differently, being more daring and eating more – a strategy of a larger part to help feed their accelerated life history, says Pauli.

The effects of harvest on fish behavior also depend on the methods used. Unlike trawling, where fishermen target fish benches, Behavioral changes are more pronounced With more passive methods such as fishing, trapping and gills net that benefits from the individual behavior of fish, explains the scientist of fisheries Robert Arlinghaus of Leibniz Institute of Eater Ekater Ecology and Inland Fisheries in Germany.

By Carefully following the activity of Pike In a German lake, Arlinghaus and his colleagues learned that the most active and daring pike tended to be captured by fishermen, while more timid fish were left behind. Because the daring and shy behavior is partly determined by the genes of a fish, “we expect that in this population, the fish become more timid over time”, explains Arlinghaus, who is also affiliated with the Humboldt University of Berlin.

In another Lac experience in Illinois, Arlinghaus and his colleagues studied bass by high ear were the most likely to go after vibrant artificial lures. Among men, Aggressive individuals were most eager to bite. The same males were also the best parents, keeping their nests and defending their offspring with exceptional devotion. Unfortunately for fish, this means that fishermen “probably capture the fish that are better dads,” explains Arlinghaus.

Prove that fish evolve is delicate, especially in nature.

The social habits of a fish can also affect their chances of being captured. In experiences with zebra fish – a popular subject of laboratory studies – the Shaun Killen environment of the University of Glasgow and his team found that More social fish tend to be captured by trapsSomething that Crespel has also seen Simulated chalt experiences. As soon as an individual enters a trap, observed Killen, others follow. And if a fish finds a way out but their friends remain trapped, this fish will come back inside. “The worst case is that there could be an evolution against being social,” he says, although much more research is necessary to know if this happens in the real world.

Arlinghaus, meanwhile, studies how fishing could affect Other aspects of cognition and intelligence of fish. If species evolve to reproduce at previous ages, they can invest more energy in rapid reproduction and less in brain development, and ultimately become less intelligent. But in certain situations where recreational fishermen release fish after capture, intelligent fish may have an advantage by learning to escape the hooks, which makes them more likely to survive and reproduce. These populations could theoretically evolve to become smarter over time, he says.

To what extent these changes really occur in nature is a mystery. But if the spirit of fish, behaviors and bodies change indeed, it could have large -scale effects. The most obvious consequences are for fisheries: if they target the most important and easier to capture individuals, the populations will possibly compose smaller and harsher fish to capture. “So it will not only be less money by fish, but you will have to work for more hours to be able to catch this fish,” explains Pauli.

These effects can be particularly difficult to reverse if the fish have actually changed these features, adds Crexel. If the small timid fish are simply those which are left behind, but the changes are not part of their genetic heritage, they could relatively easily collect their old lines if they were left alone, but if the gene pool has changed, recovery could take a long time.

More important aquatic food chains can also be affected. Fish with a shorter lifespan with a live trend and Die-Young could consume more food, which led the populations of their prey. Predators may be easier to catch fish that have become less social and therefore less likely to swim in major upset protection. On the other hand, if the predatory fish become more shy, they could hunt and eat less from their prey. This could lead to an increase in populations of herbivorous fish, speculates Arlinghaus, with downstream effects such as the overgrazing of marine vegetation. “There are so many things we don't know,” says Killen.

As well extended by the effect of fishing on aquatic ecosystems, Crepel stresses that these changes are not natural – and they act on ecosystems which are already transformed by overfishing, climate change and pollution. To avoid composing these problems by changing the fish in a non-natural way, known as Crexel, perhaps the peaches should consider changing their practices to target a wider variety of characteristics of the fish. Catching fewer fish and avoiding overfishing would also help reduce pressure on fish populations.

“We have to start thinking about how not to have too much impact on the evolution of the fish,” explains Crexel.

Lead image: Annette Shaff / Shutterstock

• Katarina Zimmer

  Published on May 30, 2025

  Katarina Zimmer is a journalist in independent science and environment.