It turns out that the archerfish, which is famous for hunting insects by shooting water at them to make them fall into the water, uses the same technique to hunt for prey underwater as well.
This was what the scientists at the University of Bayreuth in Germany discovered when they observed the behaviour of some wild-caught fish recently. “We usually get wild-caught fish from Thailand, and when they first arrive in the lab we often see them ‘shooting’ at things on the ground of their tanks, such as leaves or small fragments of wood,” said Prof Dr Stefan Schuster.
Intrigued to find out more about this behaviour, the scientists set up an experiment in which five of the fish were presented with bowls that had prey hidden beneath different types of sediment. Soon, they observed the fish shooting mouthfuls of water into the sediment to dislodge the prey to expose and consume them. The fish used the same technique as when they hunted prey above the water; the only difference was that when the prey was underwater, the prey needed to be six to 40 millimetres away. In comparison, if the prey was above the water, the fish was able to shoot the water as far as two metres away.
The researchers also discovered that the archerfish adapted the water blast based on the type of sediment the prey hid in. If the sediment was coarse-grained, the water blast was short; if the sediment was fine, the water jet was longer.
Although the researchers have published a paper on their findings, more questions remain about the archerfish's unique ability. For instance: how did the fish know whether the silt was fine or coarse? Does it use this ability for other purposes, like defence? Which came first – aerial or underwater shooting?
The researchers will continue in their investigation to learn more about the fish's behaviour.