抄録
To determine the favorable sediment environments for juveniles of the brackishwater bivalve Corbicula japonica, the relationship between the presence of juveniles and limiting factors of the sediment environment that are negatively correlated with juvenile density was investigated in Lake Abashiri, one of the northernmost areas of this bivalve's distribution in Japan. Correlations between juvenile density and sediment factors were estimated by Spearman's rank correlation coefficient. Logit models were made between the presence or absence of juveniles, as the dependent variable, and limiting sediment factors, as independent variables. The models were compared by the Akaike Information Criterion (AIC) . The values at probability 50% of the logit models (V50s) and the standard errors of the univariate logit models were calculated for each sediment factor. We defined favorable sites as those where any of these values are less than the V50s, which seem to provide good criteria to distinguish between favorable and unfavorable sediment conditions for juveniles. The V50s for limiting factors were: organic carbon 1.10 %, organic nitrogen 0.15%, organic carbon / nitrogen ratio 7.43, ignition loss 4.45%, water content 40.97%, and silt-clay (particle diameter<0.063mm) plus very fine sand (0.063-0.125mm) 36.88%. A significant logit model could not be made for total sulfide. These criteria may provide important information for the management of C. japonica resources.
