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Seasonal changes of thyroid hormones in field‐collected Atlantic cod in relation to condition indices, water temperature and photoperiod
Author(s) -
Comeau L. A.,
Campana S. E.,
Hanson J. M.,
Chouinard G. A.
Publication year - 2000
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2000.tb00261.x
Subject(s) - gadus , biology , photoperiodism , atlantic cod , zoology , thyroid , thyroid hormones , hormone , seasonality , triiodothyronine , endocrinology , fish <actinopterygii> , fishery , ecology , botany
Serum T 4 and T 3 in wild Atlantic cod Gadus morhua ranged from 1 to 12 ng ml −1 and from 2 to 27 ng ml −1 respectively over a 3‐year period. In general, the concentrations increased from summer (T 3 ) or early autumn (T 4 ) to maxima in mid‐winter and declined abruptly during spring. The T 4 /T 3 monthly means were lowest in summer and highest in winter. The seasonal patterns of thyroid hormones were weakly correlated with changes in water temperature. However, both T 4 and T 3 co‐varied simultaneously with photoperiod. In addition, T 3 was correlated with the hepatosomatic index and condition factor during summer and autumn. It is suggested that the seasonal changes in the release of T 4 from the thyroid were photoperioddriven, and that the course of T3 was regulated by the metabolic state of the fish during the somatic growth period.