Experimental observation about landing-behavior of a gobiid fish, Mugilogobius abei -Ⅰ

Abstract

Abe-haze, Mugilogobiusu abei, a gobiid fish sometimes moves out of the water and can stay in air for a considerable time, especially in overcrowded conditions. Why do they emerge and stay in air? To investigate the reason, I made some observations about Abe-haze fish’s behavior in two types of test tanks with land. One tank has a slope which divides the water-body into two parts (lager and smaller). The upper part of the slope emerges from the water forming dry ground (=land). Under extremely high density in the smaller water-body, nearly 80% of the fishes emerged over the course of a day. And several days, some of them moved over the land and reached the other (lager) water-body. In another similar tank with land covering the part of the surface area, the population density was about one quarter. In this case landing was done quickly and more individuals remained in the water. These observations indicate that the Abe-haze fish emerges to avoid competition and that they may make excursion overland to find another water-body (tide-pool).