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Interaction between temperature and photoperiod on growth and feeding of Atlantic cod (Gadus morhua): possible secondary effects

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Abstract:

Interactions between temperature and photoperiod on growth of Atlantic cod (Gadus morhua) juveniles (initial weight 9.1 g) were studied by rearing juvenile cod 3 months under simulated natural photoperiod (LDN) and continuous light (LD24:0) at 7, 10, and 13 °C. Juvenile Atlantic cod exposed to LD24:0 had higher growth rate and better feed conversion efficiency compared with cod reared under LDN. Optimal temperature for growth of juvenile Atlantic cod in the size range 5–50 g was influenced by photoperiod and was estimated to be 12.3 °C under LD24:0 and 15.7 °C under LDN. After termination of the laboratory study, the fish were reared in sea pens at ambient conditions for 17 months. The growth-enhancing effect of LD24:0 could be traced far beyond the duration of the laboratory trial, as the final mean weights in June 2005 of the fish reared at LD24:0 and 13 and 10 °C in the laboratory trial were 8% and 13% higher than those of the respective LDN groups. Our study indicates a physiological mechanism that might be linked to cod migrations, as maximal growth and feeding efficiency will be attained in areas during a season with extended day length or continuous light.

L'élevage de jeunes morues franches (Gadus morhua) (masse initiale de 9,1 g) durant 3 mois sous une photopériode naturelle simulée (LDN) ou en lumière continue (LD24:0) et à des températures de 7, 10 et 13 °C a permis d'étudier les effets des interactions entre la température et la photopériode sur la croissance. Les jeunes morues franches exposées à LD24:0 ont un taux de croissance plus élevé et une meilleure efficacité de conversion de leur nourriture que les morues gardées à LDN. La température optimale pour la croissance des jeunes morues franches dans l'intervalle de tailles de 5–50 g est influencée par la photopériode et est estimée à 12,3 °C à LD24:0 et à 15,7 °C à LDN. Après la fin de l'étude de laboratoire, les poissons ont été gardés dans des enclos marins aux conditions ambiantes pendant 17 mois. L'effet de stimulation de la croissance par LD24:0 se manifeste bien au-delà des expériences de laboratoire, puisque les masses moyennes finales en juin 2005 des poissons élevés en laboratoire à LD24:0 et aux températures de 13 et de 10 °C étaient respectivement de 8 % et de 13 % plus élevées que celles des groupes LDN correspondants. Notre étude indique l'existence d'un mécanisme physiologique qui pourrait être relié aux migrations des morues, puisque les maximums de croissance et d'efficacité alimentaire sont atteints dans des zones où il y a une saison de lumière continuelle ou de photophase étendue.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: February 1, 2007

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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