Territorial behaviour of released juvenile red sea bream.

Abstract

We observed the behaviours of released juvenile red sea bream Pagrus major, stocked in a small fishing port. Three types of individuals showing distinct behaviours were distìnguished: 1) territorial individuals, 2) territorylike individuals, 3) individuals keeping no restricted cruising area. A portunid crab Thalamita sima and/or gobiid fishes were observed to dig the sandy substratum to make their shelters at the center of the defended area of the territorial individuals. This behaviour might make deep burrowing benthos to which P. major cannot generally gain access readily available to the territorial ones. The territorial individuals tended to defend smaller area, attack more frequently and show smaller number of feeding bout than the territorylike ones. Concerning the territorylike individuals, as the density became lower, the defended area of each individual became larger, but the number of both attacks and feedings smaller.