When it comes to fish families, the bigger and bossier the better

A research team from McMaster University and the University of New South Wales has found that among cichlids, a species that lives in groups, members make strategic decisions about their living situation.

The results appear in the current issue of Biology Letters.

The helper class of cichlids showed a preference for joining groups of familiar individuals, some likely to be family members. But when given the choice between unfamiliar social groups the helpers chose groups where the members were bigger and bossier.

At the beginning of the experiment, which was conducted in Zambia's Lake Tanganyika, researchers expected that individual cichlids would base their group-living arrangements on whether they could improve their social rank and thereby expedite their attainment of breeding status.

However, when faced with a choice between unfamiliar groups they chose the group that did not enhance their rank but that contained larger group members.

“It seems that cichlids potentially prefer groups of dominant members for reasons of survival due to the increased protection from predation when larger group members are around,” says Marian Wong, a post-doctoral fellow in McMaster's Department of Psychology, Neuroscience & Behaviour, and co-author of the study.

In other words, fish—like humans—understand that membership has its rewards.

The study was funded by the Natural Sciences and Engineering Research Council, the Canadian Commonwealth Post-Doctoral Fellowship, and the Ontario Ministry of Research and Innovation Post Doctoral Fellowship.