ABSTRACT
Learning about the biology of the species is essential to the success of intensive farming. This study aimed to evaluate the semen of Thai tilapia during the four seasons of the year and thereby analyze their reproductive indices. Thus, 60 breeding males of Tilapia were used and were randomly divided into four water tanks and fed with isoproteic and isocaloric feed. The experiment lasted 12 months, starting from October 2014 and ending on September 2015. Thus, it was possible to collect sperm material of animals during the four seasons, twice a month, as well as to evaluate the water quality parameters in the tanks (temperature, pH and dissolved oxygen). The semen was evaluated from a light microscope in an increase of 100 x, then was activated with water. Motility was measured subjectively in the light microscope, as well as the percentage of sperm showing progressive motility. The duration was evaluated with the addition of a timer. For analysis of the morphology of the semen, the test consisted of morphopathology observation of 100 sperm focused in various fields throughout the slide in the light microscope. Once obtained, these data were analyzed through ANOVA and Tukey test as post-hoc analysis, with the help of the software R Statistics. Water quality factors (temperature, pH and2dissolved) were acceptable and during the 12 month period the sperm of tilapia (Oreochromis sp.) had a good ability for fertilization, seen that it performed below the averageof the percentage of critical abnormalities, and quality was perceived by the parameters that also influence fertilization (motility rate, duration of motility and vigor).