The movements of 28 adult chum salmon, Oncorhynchus keta (Walbaum) tagged with electromyogram (EMG) transmitters were tracked along the Toyohira river, Hokkaido, Japan, in October of 2007 and 2008 to investigate and evaluate the upstream migratory behavior through the protection bed and fishway of ground sills. The approach time of fish that ascended successfully through the protection bed and fishway was shorter than that of unsuccessful fish. The unsuccessful fish were observed to swim in currents with high water velocity and shallow water depth at swimming speeds that exceeded their critical swimming speed (U (crit)) during the approach to these structures. In consequence, unsuccessful fish frequently alternated between burst and maximum sustained speeds without ever ascending the fishway, and eventually became exhausted. It is important that fishway are constructed to enable chum salmon to find a passage way easily, so that they can migrate upstream rapidly without wasting excessive energy.

Abstract:The spawning ground of chum salmon (Oncorhynchus keta) is usually 31 located farther downriver than that of masu salmon (O. masou) in Hokkaido, Japan. To 32 compare the swimming abilities of these two species, the relationship between 33 swimming speed and oxygen consumption was compared using a swim tunnel in the 34 laboratory. Then, the upstream-migration behaviors of chum and masu salmon were 35 compared using electromyogram (EMG) telemetry at fish passages in the Toyohira 36 River, Hokkaido. In the laboratory study, the standard metabolic rate of masu salmon 37 was lower and the critical swimming speed (Ucrit) was faster than those of chum salmon. 38In the field study, the holding time needed to recover the swimming performance 39 exceeding Ucrit at the fish passages, and the trial number needed to pass the fish 40 passages were significantly lower for masu salmon than chum salmon. These results 41revealed that masu salmon are more adaptable to extended swimming in 42 high-water-velocity conditions than chum salmon and that masu salmon are better 43 equipped for a long distance upstream to their spawning ground than chum salmon.

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