MODELLING OF NUTRIENT REDUCTION RATE FROM CARCASS OF ANADROMOUS FISHES AND ESTIMATION OF INFLUENCE TO RIVER WATER QUALITY

Abstract

 Influence of river water temperature on nutrient reduction rate with decomposition of anadromous fishes was experimentally investigated. Focusing on pink salmon Oncorhynchus gorbuscha which has the largest resource of anadromous fishes in east Hokkaido, experiments on reduction rate with decomposition under temperature corresponding to river water temperature from October to November, run-up season, were conducted. Part of fishes, male/female, river/distilled water, and water temperature, were considered as experimental conditions. As a result, the larger reduction rates of NH_4-N and PO_4-P are, the higher water temperature are. Part of fishes and sex of pink salmon also greatly influence reduction rate. After 50 years from 1968, the reduction rate of NH_4-N increases approximately 40 % by estimating of variations in water temperature and discharge.