Monitoring reproductive migration is essential for the conservation of anadromous species. Shishamo smelt (Spirinchus lanceolatus) is endemic to Hokkaido, the northernmost large island in Japan. S. lanceolatus is an anadromous species that is known to migrate into rivers for a very short period in early winter. While this species has a special value for local fisheries, the catch amount has drastically declined in the last few decades. Information about S. lanceolatus reproductive migration dynamics is limited, which prevents them from being efficiently managed as a resource. In this study, we used environmental DNA (eDNA) methods as a noninvasive molecular tool for estimating presence/absence and abundance/biomass of S. lanceolatus during their migration into rivers. We developed a species‐specific qPCR system for S. lanceolatus, examining (a) temporal variation in S. lanceolatus eDNA concentrations compared with catch data gathered by traditional methods and (b) variability of migratory patterns among river systems. In a core river for their spawning migration, we consistently detected S. lanceolatus eDNA throughout the spawning season, and the temporal distribution of eDNA concentration was consistent with that of the number of migrating S. lanceolatus estimated by catch survey data. In addition, we were able to detect S. lanceolatus eDNA even from rivers without any official record of their migration. Among rivers with eDNA detection, the relative eDNA concentrations varied, indicating that the population biomass differs largely among the river populations. Our study suggests that eDNA detection systems are useful for tracking reproductive migration of S. lanceolatus at fine spatio‐temporal scales.

During 2004During -2006 adult chum salmon, Oncorhynchus keta (Walbaum), were tagged with electromyogram (EMG) transmitters and depth/temperature loggers and tracked along both the channelised and reconstructed segments of the Shibetsu River, Japan to assess the effects of the river re-meandering construction on upstream migration. Holding time of chum salmon in the reconstructed segment was longer than in the channelised segment. Further, greater diversity of physical condition in water velocity was observed in the reconstructed segment in 2005. Swimming speeds decreased during holding and often exceeded the critical swimming speed (U crit ). It appears that the physical characteristics developed in the reconstructed segment may be suitable for holding of chum salmon. Further, swimming speed exceeding U crit prior to holding may be exhaustive so holding behaviour may be important for muscle recovery as well as for efficient swimming to reduce the energetic cost during upstream migration. K E Y W O R D S : chum salmon, EMG transmitter, radio telemetry, reconstruction, upstream migration.

–  A segment of the Shibetsu River was restored to reconstruct the ecological condition of the previously canalized river stretch to a more natural, meandering state. In this study, we investigated the upstream migration of chum salmon (Oncorhynchus keta) using radio transmitters to track the horizontal position of fish and data loggers to detect the vertical swimming depth of fish, simultaneously. The monitored salmon travelled near the bottom of the water column and along the riverbanks, and tended to hold in deep, slow current areas in the canalized river. In the restored segment, the fish swam at more shallow depths and against stronger currents. Although the three tracked fish all reached the confluent point and chose to enter the restored segment, they did not remain in the segment for long. This indicates that the restored area facilitates the upward migration of the chum salmon.

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.

This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Hydrobiologia AbstractThe migratory behavior and swimming patterns of anadromous upstream migratory fish have been poorly described in the Shibetsu River in eastern Hokkaido, Japan. In this 2004 study, we used electromyogram (EMG) transmitters and depth/ temperature (DT) loggers to compare the upstream migratory behavior of adult male chum salmon (Oncorhynchus keta) and pink salmon (O. gorbuscha) in the canalized and reconstructed segments of the Shibetsu River, where a part of canalized section was preliminary reconstructed meander to restore a more natural section. The EMG transmitter and DT logger were externally attached to the left side of the body, below the front edge of the dorsal fin. Fish of both species often migrated along the riverbanks and near the bottom of the water column, sometimes engaged in holding behavior, which was defined as cessation of swimming during their upstream migration for 5 minutes. ). Pink salmon swam faster as well as in relatively deeper than chum salmon, suggesting that they expend more energy than chum salmon in the reconstructed segment. Based on these results, it seemed likely that the upstream migration behavior of chum and pink salmon was different with species-specific strategies.2