How Fish Keep Each Other in Line

Follow the law and society works. Step out of line, and there are consequences. This is the rule in human society, but apparently, fish can threaten punishment too.

According to new research from the ARC Centre of Excellence for Coral Reef Studies at James Cook University and the Biological Station of Donana, Spain, Australian goby fish threaten troublemakers with banishment.

These tiny reef fish maintain a stable social order, with only the top male and female permitted to mate. All the other males and females have to wait their turn to reach to top of the fishy queue. Whenever the top fish dies, the next moves up in line and get its opportunity to mate.

One of the researchers, Dr. Marian Wong, found that for each step in line, the fish size decreases by 5%. In order to maintain their position in line, fish will even starve themselves to avoid "jumping the queue".

Any fish that breaks the social compact is sent packing, left alone outside the communal protection of the group; it's easy prey for predators. This is such a risk that the fish manage their position in line very carefully.

According to Dr. Wong:

"Social hierarchies are very stable in these fish and in practice challenges and expulsions are extremely rare – probably because expulsion from the group and the coral reef it occupies means almost certain death to the loser. It is clear the fish accept the threat of punishment and co-operate as a way of maintaining their social order – and that’s not so very different to how humans and other animals behave."

This kind of experiment has been very difficult to perform in higher animals because it's tough to spot the behaviors.

The research, entitled *The threat of punishment enforces peaceful cooperation and stabilizes queues in a coral-reef fish *was published in the Proceedings of the Royal Society B.