Territorial behavior in juvenile red sea bream Pagrus major and crimson sea bream Evynnis japonica

The territorial behavior of juvenile red sea bream Pagrus major and crimson sea bream Evynnis japonica was examined at Morode Cove, Ehime Prefecture. Four exclusive types of behavior (attack, mutual attack, head down threat and mutual display) and one escaping behavior (fleeing) were observed in both species. Juvenile of the two sea bream could discriminate between each other and change their territorial behavior depending on the presence of conspecifics or heterospecifics. The territorial behavior toward conspecifics was more aggressive than toward heterospecifics. Interrelationships between the two sea bream were more aggressive than in other heterospecific cases. The two sea breams performed following behaviors toward solo and schooled mullid species. E. japonica ascended the water column more frequently than P. major in high frequency, The former joined conspecific aggregations foraging for planktonic animals around their territories. These observations suggest that territorial individuals of the two sea bream could discriminate intruders utilizing similar food resources in order to maintain their territories.