Temperature-related loss of smolt characteristics in Atlantic salmon (Salmo salar) in the wild

Abstract

Atlantic salmon (Salmo salar) that had previously been released as fry in tributaries of the Connecticut River were captured from 1993 to 1997 during their normal spring smolt migration 198 km from the mouth of the river. Smolts had peak levels of gill Na+,K+-ATPase activity and salinity tolerance early in migration (early May), indicating physiological readiness to enter seawater. Significant decreases in gill Na+,K+-ATPase activity (29-66%) and salinity tolerance were seen in smolts at the end of the migratory period (late May and early June). Reduced gill Na+,K+-ATPase activity occurred earlier in warm years and was directly related to the degree-days during migration (r2 = 0.75). Reduced gill Na+,K+-ATPase activity was found at the end of migration in warmer, southern rivers (Connecticut River and Penobscot River, Maine) but not in northern rivers (Catamaran Brook, New Brunswick, and Conne River, Newfoundland). Both hatchery- and stream-reared fish held in the laboratory exhibited a more rapid loss of physiological smolt characteristics when held at higher temperature. The results indicate that late migrants in southern rivers lose physiological smolt characteristics due to high temperatures during spring migration. Delays in migration, such as those that occur at dams, may have negative impacts on smolt survival in warmer rivers.

Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam

“…An often neglected cause of migratory failure in impounded rivers is the delay caused by the presence of dams (Marschall, Mather, Parrish, Allison, & McMenemy, 2011;Venditti, Rondorf, & Kraut, 2000). In addition, an increase in time spent migrating may lead to loss of migratory motivation, reversion of physiological adaptations, lost feeding opportunities and mistimed sea (or lake) arrival in relation to food availability or other environmental condition (McCormick, Cunjak, Dempson, O'Dea, & Carey, 1999;Muir, Marsh, Sandford, Smith, & Williams, 2006;Tétard, Feunteun, et al, 2016). In addition, an increase in time spent migrating may lead to loss of migratory motivation, reversion of physiological adaptations, lost feeding opportunities and mistimed sea (or lake) arrival in relation to food availability or other environmental condition (McCormick, Cunjak, Dempson, O'Dea, & Carey, 1999;Muir, Marsh, Sandford, Smith, & Williams, 2006;Tétard, Feunteun, et al, 2016).…”

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

“…Specifically, Roper and Scarnecchia (1998) found that during a 4-year study on Chinook smolts, higher average spring temperatures were associated with earlier emigration dates from an Oregon river system. Likewise, McCormick et al (1999) found that wild populations of Atlantic salmon from warmer, southern rivers migrated earlier than populations from cooler, northern rivers. These studies also showed that at lower temperatures, the smolting process takes longer and the migration window is extended.…”

“…Water temperature has also been found to have an impact on smolting, however, rather than directly initiating the process it has been found to be important in determining the rate of the physiological changes taking place (McCormick et al 1997;McCormick et al 2002;Shrimpton and McCormick 2003). In particular, studies have shown that while increased temperature results in the earlier development of smolt characteristics, extended exposure to higher temperatures will result in the loss of those same characteristics (Zaugg et al 1972;McCormick et al 1999). Studies have also shown that low temperatures will limit the physiological response to increased photoperiod .…”

Survival of Migrating Atlantic Salmon Smolts through the Penobscot River, Maine: a Prerestoration Assessment

“…Such an outcome may have broad implications for managing smolt passage in the Penobscot River and elsewhere. Delays can increase exposure to predators (Riemann et al 1991;Blackwell and Krohn 1997;Venditti et al 2000) or can cause physiological loss of osmoregulatory capacity (McCormick et al 1999). Daytime migratory delays could increase exposure of smolts to avian predators.…”

“…During migration, immediate or delayed mortality may result from predation or direct injury imposed by turbines or other dam-related structures (Ruggles 1980;NMFS 2000). Migratory delays caused by physical or behavioral barriers may further increase predation risk (Nettles and Gloss 1987;Blackwell and Krohn 1997) or may cause poor synchrony of physiological tolerance to salinity (McCormick et al 1999), possibly increasing estuarine mortality (Budy et al 2002;Ferguson et al 2006). Identification and mitigation of such impediments (2004) identified dams as one of the potentially most acute impediments to Atlantic salmon restoration in Maine.…”