天竜川における湧水流路の環境条件とアユ産卵床形成との関係解明

Abstract

Formation of spawning redds for ayu fish can be affected by both environmental factors and morphological factors at spring water channel. Thus, regression analysis of presence of spawning redds and each factor allows for the identification of the underlying effects at both local and sandbar scales. To evaluate the directly or indirectly effects of water quality, physical variables, meso-scale riverbed configuration and sandbar variations on spawning redds, we examined the relationships between distribution of spawning redds and environmental factors. The logistic regression model indicated that the distribution of redds is affected by turbidity, velocity, depth, meso-scale rived parameters and several sandbar variation parameters but not affected by water temperature, number of channels and number of sandbar variations. Recognition of the distribution pattern of spawning redds at a sandbar scale at spring water channel may be useful to determine areas on which to focus both future river and reservoir sediment management strategies.