モ場の魚の群集生態学的研究-I

Abstract

The Zostera growing area seems to be a suitable field for marine fish-community studies, since it is semi-closed especially for small sized fish which can be easily collected. In the Zostera area of Matsushima Bay, Miyagi Prefecture, it was revealed by the seine collections repeatedly made during the warm seasons of 1959 that the young of Japanese sting-fish, Sebastes inermis, “Mebaru”, is a dominant species inhabited. A fish group was confined within the fish frequently occurred with the dominant species and named as the “Mebaru” community, which is to be regarded as a trunk in the structure of fish production system in the Zostera area. Each fish belonging to the “Mebaru” community shifts slightly its composition of food item, sharing subtly the food substances produced in the Zostera area as shown in Fig 2. This type of food segregation suggests that each fish lives competing with each other for foods, resulting in a selective feeding. Ecological order for feeding among predators would be measured in terms of the order in the ecological niche of their preys. At present, an ecological order among fish constituting the “Mebaru” community was presented as to be in the following series ;—Pseudoblennius cottoides > Hexagrammos otakii > Sebastes inermis > Enedrias nebulosus > Chaenogobius murorana > Aboma lactipes > Fugu niphobles > Tridentiger trigonocephalus > Acanthogobius flavimanus. The dominant species, Sebastes inermis, living in the Zostera area seems to be limited its feeding activity by Pseudoblennius cottoides and Hexagrammos otakii and also seems to suffer from diminutions of food supply reduced by Enedrias nebulosus and Chaenogobius murorana.