ABSTRACT

Lateralization (eye preference) or handedness has been studied over the years in different species of vertebrates in 9ther to study how they perform multiple tasks simultaneously with respect to their survival, tenacity, responses, detection, etc. Mirror and dyadic test were used to test, determine, and compare the aggression and lateralization levels of Nile tilapia (Oreochromis niloticus) with its own mirror image, an opponent and potential natural predator. 120 apparently healthy Nile Tilapia about the same weight and length were used for the experimental trails.

Results showed that individuals showed more aggression towards their mirror image than they did towards their opponents in the dyadic test. Left and right eye use in the bot!; tests were different with individuals in both showing different levels of lateralization. The individuals in the dyadic test used there left eye as much as they used their right eye when viewing their opponents. However, tests fish in the mirror test used their left eye more than they used their right eye when viewing their opponents, so they are left eye biased.Furthermore, test fish were found to also use their left eye more than they used their right when viewing a predator. Findings were discussed on how the Nile Tilapia showed the various levels of aggression and interaction with their mirror images, opponents and the eye preferences during both aggression test' and while viewing a predator.