Different Duration of Memory for Conspecific and Heterospecific Fish in the Paradise Fish (Macropodus opercularis L.)

During an encounter with a conspecific male paradise fish memorize some features of their opponent. This is revealed by the shorter contest and significant changes in their behaviour at a second encounter with the same opponent. Memory of an opponent lasts for one day but is undetectable after a week. In contrast memorization of other species could easily be preserved for several months. A possible explanation of these different durations is discussed in relation to their functions in the life of the fish.