In order to elucidate the selection of spawning substrate by female cuttlefish Sepia esculenta, their behavior and trigger stimulus during a spawning sequence were examined in indoor tanks. Fe male approaches substrate, spurts water towards substrate, takes sediment in arms, covers eggs with sediment, spurts water towards substrate again, and undergoes egg deposition on substrate to complete one spawning. Females which finished copulation were visually attracted to more visible substrate. The height of a substrate was not an important factor for the attraction. Substrates which swung by the spurting water were not accepted by females. Females exhibited taking sediment even though there was no sediment on the tank bottom. It was concluded that female cuttlefish prefer long, fine, and immobile materials as spawning substrates.

In the present study, trapping experiments and observations on the behavior of immature cuttlefish Sepia esculenta towards the traps were made under field and laboratory conditions. Trapping experi ments clearly demonstrated the entry of immature cuttlefish into the basket traps. The entry rate was sig nificantly higher in immature than in mature cuttlefish studied in the same laboratory conditions. When entering and leaving the trap, cuttlefish swam straight primarily with arms in front, thus suggesting their active movement.After entry, cuttlefish remained stationary at the bottom. Females stayed in the trap longer than 3 days, while males left within 3 days. The existence or the position of branches did not influence the entry of cuttlefish into the traps. These results may rule out the possibility that spawning is a motivation for the entry of cuttlefish into the traps.

The Kushiro Wetland, one of the precious wetlands in Japan, is located in the east of Hokkaido, downstream of the Kushiro basin. A number of meandering channels were retained without manipulation. Nowadays, the Kushiro wetland is faced with many problems. The drying phenomena impact many kinds of animals and plants, especially in reducing the number of habitats of precious spieces. The phenomena stem from sediment deposition on the surface layer due to the inundation and the decrease of the capacity of preserving water. The wetland acts as a vast area, and allows overflowing freely during the flood period. It is an important factor for the drying phenomena of the wetland.The purpose of this study is to develop a numerical model to simulate the flooding of the Kushiro wetland, and to investigate the relation between the accumulation of suspended sediment and the drying phenomena with both of whole and limited areas in the wetland.

Fishing port facilities are the main coastal structures in fishery area forming large stocks for which a considerable degradation is concerned. Introduction of the stock management capable of reducing the life cycle cost and enhancing the life and durability of the existing structures is expected. This paper discusses the future prospects and problems with the stock management when applied to the fishing port on the basis of the actual operations. For a smooth introduction of the stock management to the fishing port facilities, a series of systematic measures are introduced including accumulation/utilization of the surveillance data, appropriate diagnosis of the degradation, rational prediction/countermeasures for the degradation , and estimation/yearly stabilization of the LCC .

No abstract