May 4 (UPI) -- Bravery is often a deadly choice for small or medium-sized fish. New research out of Sweden suggests shier fish are likelier to live longer than their bolder peers.
Researchers at Lund University captured and marked several common roaches, a ubiquitous freshwater fish native to Europe. The scientists then observed each identified specimen's personality. Finally, researchers watched the fish to observe their fate in the wild.
Specimen with bolder, more aggressive dispositions were more likely to end up eaten by cormorants.
Researchers measured the fishes' personalities in the lab. Common roach specimens were placed in a dark tank and scientists measured how long it took each fish to swim out of the tank. The bolder fish left the darkened tank more quickly.
Biologists have long assumed boldness or bravery is a weighted decision. An act of bravery can offer a reward, but it comes with an increased risk of predation.
The fish were tagged with small portable sensors. Fish-eating cormorants regurgitated the tiny sensors. Scientists walked the edges of the lake and collected sensors, which revealed which fish had been caught and consumed.
Scientists published the results of their study in the journal Nature.
"Our study is unique in that we focus on an important behavior and not morphology, but also because we allow the interplay between predator and prey to take place in their natural habitat, their home lake," researcher Kaj Hulthén said in a news release.