Growth of the stocked ayu‐fish in pond already inhabited by some fish of the same species

Summary In a small test pond, growth of the newly stocked ayu‐fish was compared with that of the fish which was stocked earlier in time and had inhabited in the pond. The test was repeated under conditions of three different levels of density. In every tests, the newly stocked group of fish was, at least in the first three weeks, more or less inferior to the inhabited group in growth. The cause of this phenomenon was assumed to be related with the difficulty for the later stocked ayu‐fish to find proper territory to defend in the pond against other members of the same species of fish.