Evaluating method of the marine environmental capacity for coastal fisheries and its application to Osaka Bay

Abstract

The methodology for the estimation of “the marine environmental capacity for coastal fisheries (E.C.)” is proposed. The characteristics of the methodology are as follows: 1) selecting and analyzing environmental factors affecting the growth and survival of fishery organisms at various developmental stages; 2) modeling the correlation of fishery organisms with their environmental factors on the basis of accumulated knowledge and experience; 3) estimating the fluctuation of fish population related to environmental conditions. For the above estimation, the environmental limits sustainable for the fisheries resources are determined by using models for the life cycle of fishery organisms. This methodology is applied to Osaka Bay. In this bay two factors are suggested to be essential to E.C. of marbled sole, Limanda yokohamae, which is representative of demersal fishes. One is the reclamation from the sea which makes narrower spawning and nursery grounds, and the other is the increased pollution load which results in a deficiency of dissolved oxygen in the bottom layer and reduces the biomass of benthonic organisms as food. The practical use of E.C. method as a tool for the environmental assessment is also discussed.