Researchers from the Konrad Lorenz Institute of Ethology in Vienna recently published a study on the effects of cichlid sex and size on their shoaling and dispersal behaviors. The paper, titled “Sex biases in kin shoaling and dispersal in a cichlid fish” and published in the December 2014 issue of the journal Oecologia, studied the cichlid Neolamprologus caudopunctatus in Lake Tanganyika, Africa. The researchers genetically sampled over 900 breeders and shoaling fish, and also documented their sex and body size. After extensive data collection and analysis, they discovered some interesting behaviors.
They were surprised to find that female cichlids dispersed longer distances from their place of birth than the males did. While dispersal is a common behavior, it is more common to see male-dispersal. In this case, the females exhibited 11 times higher migration rates than the males. It is theorized that the purpose of dispersal is often to avoid inbreeding and competition for resources among relatives, and also to increase access to available resources and mates.
The second phenomenon the researchers discovered was the presence of kin shoaling among small female cichlids. Small, young, female cichlids tended to shoal with their female siblings. However, there was no observation of small males shoaling with kin. The males seemed to shoal with other non-sibling males, and no kin-shoaling was observed for larger, older fish. Dispersing fish may tend to shoal to avoid predation. The researchers theorize that the small females may shoal with siblings in order to increase the likelihood of one of their family surviving, and therefore increasing the survivability of their genetic material. The abstract of the paper reads: “Further, kin shoaling may augment inclusive fitness by reducing predation of relatives.”
This may be one of the first studies to give evidence towards a relationship in sex-based dispersal and kin shoaling. The names of the researchers were: Franziska Lemmel-SchÃ¤delin, Wouter van Dongen, Yoshan Moodley and Richard Wagner.