<< Contrary to our predictions, fish that were the most familiar with each other showed the highest levels of aggression. Additionally, fish that were less familiar with each other exhibited the highest group cohesion and took the longest to begin feeding, compared to the more familiar fish. >>
Carolina Doran, David Bierbach, Kate L. Laskowski. Familiarity increases aggressiveness among clonal fish. Animal Behaviour. Volume 148, February 2019, Pages 153-159. doi: 10.1016/j.anbehav.2018.12.013
https://www.sciencedirect.com/science/article/pii/S0003347218303725?via%3Dihub
Fish with a high level of familiarity are more aggressive towards each other. Forschungsverbund Berlin e.V. (FVB). Feb 19, 2019
https://m.phys.org/news/2019-02-fish-high-familiarity-aggressive.html