Accelerating smolt development and downstream movement in yearling chinook salmon with advanced photoperiod and increased temperature

Ionoregulatory changes in different populations of maturing sockeye salmonOncorhynchus nerkaduring ocean and river migration

“…The factors measured in the present study of freshwater migrating fish suggest continued physiological changes throughout migration. Physiological changes associated with migration distance have previously been observed in smolting salmonids with distance moved downstream (Muir et al, 1994). Therefore, the decline in gill Na + ,K + -ATPase activity as sockeye migrate to spawning areas may reflect physiological adjustments that continue to occur as the fish migrate.…”

The role of temperature and flow on the migration of Chinook salmon (Oncorhynchus tshawytscha) smolts.

“…Despite the negative coefficient, increasing flows likely do provide benefits such as increased rate of migration as suggested by other studies (Muir et al 1994;Connor et al 2003). However, given that smolts from the Nechako River must migrate approximately 1,000 km to reach saltwater (Figure 2), it is reasonable to expect they would need to begin migrating earlier than populations with shorter migration routes.…”

“…Previous studies have shown smolting will not occur in the absence of a photoperiod signal and temperature alone cannot initiate the physiological changes associated with smolting, but instead controls the rate of change (Muir et al 1994;McCormick et al 2002).…”

“…Since anadromous fish in these systems have evolved to respond to changes in environmental cues during the spring to time the physiological transformation with the onset of migration, it is unknown what potential impact manipulation of temperature and flow may have. It seems reasonable to assume that synchronous changes in environmental variables such as photoperiod, temperature, flow and turbidity will provide the strongest stimulus for smolting and migration and there is some evidence that an increasing photoperiod regime in synchrony with a rise in temperature strengthens the physiological changes associated with smolting (Muir et al 1994). Yet, little is known regarding the impact on smolting if these physical changes are not synchronous or do not occur.…”

Snake River Fall Chinook Salmon Life History Investigations, Annual Report 2007.

“…In contrast to subyearlings in the Snake River that outmigrate under an increasing photoperiod, the later emergence of Clearwater subyearlings results in their outmigration occurring under a decreasing photoperiod. Increasing photoperiod and temperature have been shown to increase smoltification in salmonids (Wedemeyer et al 1980;Muir et al 1994). Thorpe (1981) discusses the influence photoperiod has on specific hormones that may be related to downstream movement.…”