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DOWNSTREAM MIGRATION OF SALMONID SMOLTS IN OREGON RIVERS AND ESTUARIES
Citation:
POWER, J. H. AND S. JOHNSON. DOWNSTREAM MIGRATION OF SALMONID SMOLTS IN OREGON RIVERS AND ESTUARIES. Presented at 2007 Estuarine Research Federation, Providence, RI, November 04 - 08, 2007.
Impact/Purpose:
to evaluate how estuarine habitat and habitat loss might affect population health of coho salmon
Description:
Migratory fish passage is an important designated use for many Oregon estuaries. Acoustic transmitters were implanted in coho smolts in 2004 and 2006 to evaluate how estuarine habitat, and habitat loss, might affect population health. Acoustic receivers that identified individual fish were deployed along the migration route. Smolts exhibited the following patterns: 1) In 2004 smolts remained in the freshwater stream for an extended time (average of nine days after tagging) before entering the Yaquina River, while downstream movement into the Yaquina was notably more rapid in 2006. 2) After moving into the Yaquina River, smolts moved quickly downstream in both 2004 and 2006, and then spent the greatest amount of time in the most seaward stretch of the estuary. Smolts moved extensively up- and downstream while in the Yaquina, and occasionally moved to a few hundred meters of open ocean before returning upstream again. Some moved passively with tidal currents, but there were also instances of fish holding position for over 24 hours. 3) Some fish were last detected at receivers closest to the ocean, and presumably entered the ocean, but others were last detected at receivers farther up the estuary. These final detections were well within the transmitter=s expected battery life so it is uncertain whether these fish successfully entered the ocean.