Seasonal cycles, mainly due to great variations in the light duration and temperature, are important and modulate several aspects of the animal behavior. In the case of poikilotherms animals such as fish this is very relevant. Thus, temperature changes fish immunity and affects disease resistance. We evaluate in this work the season variations of the European sea bass (Dicentrarchus labrax) humoral innate parameters focusing on winter months, at which the culture of this specie is more difficult. Our results showed that not all the innate immune parameters are depressed by low temperatures. Moreover, some of them are more dependent than others to the season and both temperature and photoperiod are operating together.