SEX DIFFERENCES IN THE AGGRESSION AND LATERALISATION OF NILE TILAPIA (OREOCHROMIS NILOTICUS)

This study investigated sex differences in aggression and lateralisation in Nile tilapia (Oreochromis niloticus) using mirror and dyadic tests. Eighty adult fish (40 males, 40 females) were subjected to both test types to measure aggressive behaviours and eye preference. A Generalized Linear Mixed Model (GLMM) with Poisson distribution analysed aggressive interactions, while a GLMM with binomial error distribution assessed lateralisation patterns. Results revealed significant sex-based differences in aggression, with males displaying higher aggression than females during dyadic tests (p = 0.0009). Fish generally exhibited higher aggression towards mirror images than real opponents (p = 0.0017). However, an interaction effect (p < 0.0001) indicated that males showed a relatively lower increase in aggression toward mirror images compared to females. Regarding lateralisation, no significant differences were found based on sex, test type, or their interaction, suggesting that eye preference is driven by individual variability rather than sex or context. The findings enhance our understanding of behavioural ecology in Nile tilapia and emphasize the importance of context in interpreting aggressive behaviours, potentially contributing to improved aquaculture practices and fish welfare strategies.