Photoperiod control of downstream movements of Atlantic salmon Salmo salar smolts

Journal of Fish Biology
By: , and 



This study provides the first direct observations that photoperiod controls the initiation of downstream movement in Atlantic salmon Salmo salar smolts. Under simulated natural day length (LDN) conditions and seasonal increases in temperature, smolts increased their downstream movements five-fold for a period of 1 month in late spring. Under the same conditions, parr did not show changes in downstream movement behaviour. When given a shortened day length (10L:14D) beginning in late winter, smolts did not increase the number of downstream movements. An early increase in day length (16L:8D) in late winter resulted in earlier initiation and termination of downstream movements compared to the LDN group. Physiological status and behaviour were related but not completely coincident: gill Na+/K+-ATPase activity increased in all treatments and thyroid hormone was elevated prior to movement in 16L:8D treatment. The most parsimonious model describing downstream movement of smolts included synergistic effects of photoperiod treatment and temperature, indicating that peak movements occurred at colder temperatures in the 16L:8D treatment than in LDN, and temperature did not influence movement of smolts in the 10L:14D treatment. The complicated interactions of photoperiod and temperature are not surprising since many organisms have evolved to rely on correlations among environmental cues and windows of opportunity to time behaviours associated with life-history transitions. These complicated interactions, however, have serious implications for phenological adjustments and persistence ofSsalar populations in response to climate change.

Publication type Article
Publication Subtype Journal Article
Title Photoperiod control of downstream movements of Atlantic salmon Salmo salar smolts
Series title Journal of Fish Biology
DOI 10.1111/jfb.12509
Volume 85
Year Published 2014
Language English
Publisher Wiley
Contributing office(s) Leetown Science Center
Description 19 p.
First page 1023
Last page 1041
Online Only (Y/N) N
Additional Online Files (Y/N) N
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