Toward a Positive Feedback between Fish Abundance and Dense Forest to Enhance Biodiversity: Responsible Fisheries from a Viewpoint of Nutrient Cycling

Research PaperTraditionally, fish has been considered as an item for direct or indirect human use (food, fertilizer, fishmeal and so on). Recently increasing number of studies on anadromous salmon in North America and Japan, however, suggest that fish could also support biodiversity. Marine-derived nutrients (MDN) are important contributors to maintain or enhance biodiversity in freshwater and riparian ecosystems. This can be rephrased in such a way that ocean helps to enrich terrestrial ecosystem. On the other hand, reevaluation of uo-tsuki-rin (fish breeding forest) has been under way in the last two decades or so in Japan. Women of fisheries cooperative associates and other environmentally-concerned people have been planting trees on coastal zone or sometimes on inland. Such activities are to attract fish to the water near such wooded areas. In this case forest is considered to furnish marine (or freshwater as well) fish with habitable environment by giving them shades, nutrients, shelters and so on. Based on these recent trends in research activities and popular actions, this paper characterizes responsible fisheries as a new approach to fisheries which allows a certain number of anadromous and other fish to freely make upstream and downstream migration and incorporates coastal and riparian afforestation in its practices. It then concludes that positive feedback between fish abundance and dense forest is the prerequisite for biodiversity both in terrestrial and marine environments