The Thyroid System's Role in the Downstream Migration of Atlantic Salmon (Salmo Salar L.) Smolts.
Youngson and Simpson (1984, J. Fish Biol., 24: 29-39) have shown that migrating
wild Atlantic salmon smelts exhibit large and transitory changes in serum thyroxine
(T,) levels throughout the spring season. The authors postulated that in smolts, the
thyroid system develops an increased capacity to respond to increases in water flow and that the adaptive significance of this may be to facilitate successful migration by increasing smolting fishes