Scientists explore how fish brains work –

Scientists explore how fish brains work Published:  18 July, 2007

Culum Brown

WHO ever heard of a fish being in two minds about something? Yet it seems that, like humans, fish process information – and perhaps emotions – on different sides of the brain.

Fish growing up in the wild among predators use their left eye to look at novel objects, while their offspring raised in captivity use the right eye, says New Scientist. This suggests that life experiences can affect which side of the brain fish use, and even, says Victoria Braithwaite of the University of Edinburgh, that they have emotional mindsets, since different sides of the brain may correspond to a curious or suspicious attitude.

“The lab-reared fish could process information about novel objects in the left brain [which means they are looking at things with their right eye] because they feel more comfortable, whereas their parents are more cautious.”

Humans use their left and right brain lobes differently, the most well-known consequence being handedness. Brain lateralisation has been found in an increasing number of other species in recent years.

“Especially for animals that have to cope with many predators, it is an advantage if they can use one hemisphere to keep an eye on predators while they use the other hemisphere to do other things,” says Culum Brown, now at Macquarie University in Sydney, Australia.

Brown and his team caught bishop fish (Brachyraphis episcopi), which are similar to guppies, from areas with high and low predation rates in Panama. The team bred the fish in the lab and then tested the behaviour of both the wild parents and their offspring. Fish swam towards a slatted barrier through which they could see either a novel object (a yellow cross), nothing, or another bishop fish. They could then swim past the barrier either to the left or to the right. Exiting to the left meant the fish had kept its right eye on the barrier, and vice versa.

Neither fish from areas of low predation nor their young showed much of a preference for a left or right exit, suggesting their brains were not very lateralised. However, fish that had to deal with a lot of predators in the wild favoured one eye, as did their lab-born offspring, especially when viewing the novel object (Animal Behaviour, DOI: 10.1016/j.anbehav.2006.08.014).

“This shows that a tendency for brain splitting can be inherited,” says Braithwaite. “But amazingly, the captive-born offspring preferred the right eye when their parents preferred the left. So the way the fish then use this brain division is a learned thing.” is published by Special Publications. Special Publications also publish FISHupdate magazine, Fish Farmer, the Fish Industry Yearbook, the Scottish Seafood Processors Federation Diary, the Fish Farmer Handbook and a range of wallplanners.