A study has shown that fish that exhibit bravery have lower survival rates compared to those with a higher level of shyness.
Even within a specific species, fish have individual personalities. At Lund University in Sweden, researchers have demonstrated a connection between a fish's personality (whether it was bold or shy) and the risk of being killed by predator. Simply put, the bravest fish are twice as likely to be eaten compared to the shyest ones.
In their study, the researchers caught some roaches from Lake Krankesjön in southern Sweden. These freshwater fish were placed in a dark concealed area. The researchers then noted how long it took for individual fish to swim out of the dark area. After that, a microchip was implanted into every fish and they were all released back into the lake.
Some of the fish were eaten by cormorants, which regurgitated the microchips as they rested in-between meals. By using a portable reader, researchers were able to identify which fish had fallen prey to the birds.
Based on the data gathered, they determined that the bolder individuals were twice as likely to be eaten when compared to the shyer ones.
“Our study is unique in that we focus on an important behaviour and not morphology, but also because we allow the interplay between predator and prey to take place in their natural habitat, their home lake,” said Kaj Hulthén, one of the researchers in the study.