Friendly fish are more likely to get caught

According to a new study from the University of Illinois, fish that are friendlier are more likely to end up caught on a fishing hook. The researchers also found that removing the most sociable fish from the lake could result in drastic changes for the fish left behind.

“There’s a reason everyone’s first fish is bluegill,” said study lead author Michael Louison. “They are social fish, forming big groups around structures close to shore. It seemed like their social behavior and their aggression would be super important in terms of angling vulnerability.”

The experts stocked up an experimental pond with bluegill from a hatchery and tagged the fish for identification.

“They had been living in a natural lake environment,” said Louison. “They had to find food and avoid predators in that environment. So they were ‘real fish.’”

Louison and a colleague fished the pond with typical methods used for catching bluegill over the course of five days. When a fish was caught, its identification number was documented.

At the end of the week, the pond was drained and 38 of the fish were assigned to a test group. Half of the fish had been caught at least once, while the others had never been caught.

To investigate the sociability of the fish, the team split a fish tank in half with a glass divider. A test fish was placed on one side and six random bluegills from the pond were placed on the other.

“We were looking at how much time this fish spent hanging out right next to the divider trying to associate with the fish on the other side,” said Louison. “You’d expect a social fish to be hanging out close to the glass a lot, whereas you’d expect a non-social fish to be further back.”

The experiment revealed that fish who had been caught spent significantly more time near the divider than fish who had never been caught, and multiple trials confirmed these findings.

The teem tested to see if aggression was also a factor that drove fish to take the bait more often, but no link was found.

The researchers speculated that removing the most sociable fish from a population could change the structure, at least on a temporary basis.

Study co-author Cory Suski is an associate professor in the Department of Natural Resources and Environmental Sciences.

“Broadly speaking, for animals living in groups, social individuals are really important. They help spot predators, find prey, and transmit information about these things to the rest of the group,” said Professor Suski.

Study co-author Jeffrey Stein is a fish ecologist at the Illinois Natural History Survey.

“Our previous research has shown that removing fish with certain characteristics – like parental quality or even overall vulnerability to angling – has potential to change the character of a population,” said Stein.

“Understanding how characteristics like sociability affect vulnerability to angling can lead to more effective management of high-quality recreational fisheries.”

The research is published in the journal Animal Behaviour.

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By Chrissy Sexton, Earth.com Staff Writer