Introduction:
1. Topic – Why do Atlantic salmon (Salmo salar) migrate and smolt?
2. Background –
a. In the life cycle of diadromous fishes it is essential for them to migrate between freshwater and seawater which is an adaptive behavior amongst the individuals that exploit and transition between these environment during various stages of their life cycle in order to increase their fitness ( Thorstad et al., 2012). Therefore, smolting is discussed as an adaptive behavior for downstream migration, entering the seawater environment and living in seawaters (McCormick et al., 1998).
3. This paper will discuss and analyze the explanations of this behavior in Atlantic salmon both at the proximate and ultimate level.
Proximate:
1. Before migrating to marine…show more content… It is evident that changes in environment influence the time of migration and smolting in Atlantic salmon (McCormick et al., 1998). The primary environmental factor that influence and affect the developmental and regulation of smolting in Atlantic salmon is photoperiod along side temperature (McCormick et al., 1998).
Ultimate:
1. The ‘environmental smolt-window’ is known as a period crucial for downstream migration to occur in which fitness is increased when individuals arrive at the seawater environment as conditions are optimal for both survival and growth (Otero et al., 2014).
2. There is an increase in smolt mortality due to the human interventions, infrastructural development and man-made reservoirs in Atlantic salmons (Thorstad et al., 2012).
a. There is an evident increase in predatory fish species in reservoirs such as dams, which decreases the survival of Atlantic salmons when migrating (Thorstad et al., 2012).
b. The construction of turbines increases the mortality rate for passing smolts as the large blades found in the turbines can kill them. A factor that may contribute to and increase in mortality is fish length; mortality rate increases with an increase in fish size (Thorstad et al.,
