To conserve the Japanese eel Anguilla japonica, damaged estuarine habitats need to be restored, because the estuaries are essential for not only growth of the species, but also as areas for silver eels to acclimate to seawater prior to migrating into the ocean for spawning. As a first step towards improving and restoring estuarine habitats, this study aimed to reveal the preferred gap structure within stone piles by eels at each life history stage. Comparison of the number of individuals among Ishikura nets with different-sized stones (large, 30 cm in major axis; medium, 20 cm; small, 10 cm) found that the immature adults (elvers and yellow eels) preferred those with small-sized stones the most. In contrast, the maturing adults in the middle of downstream spawning migration (silver eels) utilized only the Ishikura nets with large and medium-sized stones. These findings suggest the importance of establishing estuarine habitats with various-sized stones to allow many eels to survive to maturity in stream areas.
The payment structure of Japanese inland fishery cooperatives (JIFCs) differs from those of marine fishery cooperatives and farmers' cooperatives in Japan because of their duty to enhance resources and the angling fees. For this study, after collecting business reports of JIFCs for fiscal 2017, we analyzed the soundness of management and business size using balance sheet information. The results show a high equity ratio and high current ratio of JIFCs, indicating that the financial condition of most JIFCs is sound. Total capital and equity capital of JIFCs were smaller than those of marine fishery cooperatives. There were large differences among JIFCs in terms of business size. A high fixed ratio suggests that funding is insufficient to invest in fixed assets.