<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Triiodothyronine and thyroxine levels and morphological parameters of fish were studied from January to May to evaluate the smoltification of yearling sea trout (<italic>Salmo trutta</italic> L.) raised in two different rearing systems (recirculating and flow-through) in three different hatcheries in Latvia. Thyroid hormone levels increased from January to May in both rearing systems in fish of different sizes. There was positive correlation between the degree of silvering and fish fork length and thyroid hormone levels, but there was no correlation between condition facor and thyroid hormone levels. Fish reared in recirculating systems were significantly larger (p &lt; 0.05) and exhibited more visible signs of smoltification earlier than those reared in flow-through systems. The thyroid hormone levels and degree of silvering gradually became nearly the same by May in the sea trout from both rearing systems. Changes in thyroid hormone levels or fish size in spring cannot be evaluated separately from other signs to determine smoltification.</p></abstract>

Triiodothyronine and thyroxine levels and morphological parameters of fish were studied from January to May to evaluate the smoltification of yearling sea trout (Salmo trutta L.) raised in two different rearing systems (recirculating and flow-through) in three different hatcheries in Latvia. Thyroid hormone levels increased from January to May in both rearing systems in fish of different sizes. There was positive correlation between the degree of silvering and fish fork length and thyroid hormone levels, but there was no correlation between condition facor and thyroid hormone levels. Fish reared in recirculating systems were significantly larger (p < 0.05) and exhibited more visible signs of smoltification earlier than those reared in flow-through systems. The thyroid hormone levels and degree of silvering gradually became nearly the same by May in the sea trout from both rearing systems. Changes in thyroid hormone levels or fish size in spring cannot be evaluated separately from other signs to determine smoltification.

Triiodothyronine and thyroxine changes in yearling sea trout (<italic>Salmo trutta</italic> L.) during spring

Latvia University of Life Sciences and Technologies

Institute of Food Safety, Animal Health and Environment BIOR

Fisheries & Aquatic Life

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Triiodothyronine and thyroxine changes in yearling sea trout ( L.) during spring

Triiodothyronine and thyroxine levels and morphological parameters of fish were studied from January to May to evaluate the smoltification of yearling sea...

Triiodothyronine and thyroxine changes in yearling sea trout (Salmo trutta L.) during spring

Published Online: Aug 22, 2018

Page range: 101 - 109

Received: Dec 29, 2017

Accepted: Jun 12, 2018

DOI: https://doi.org/10.2478/aopf-2018-0011

Keywords
morphology, salmonids, silvering, smoltification, thyroid hormones

© 2018 Archives of Polish Fisheries

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Triiodothyronine and thyroxine changes in yearling sea trout (Salmo trutta L.) during spring

Published Online: Aug 22, 2018

Page range: 101 - 109

Received: Dec 29, 2017

Accepted: Jun 12, 2018

DOI: https://doi.org/10.2478/aopf-2018-0011

Keywordsmorphology, salmonids, silvering, smoltification, thyroid hormones

© 2018 Archives of Polish Fisheries

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
morphology, salmonids, silvering, smoltification, thyroid hormones