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Effect of ambient oxygen on growth and reproduction in Nile tilapia (Oreochromis niloticus)

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Abstract:

Growth, size at maturity, gonadosomatic index (GSI), egg size, and absolute fecundity of Nile tilapia (Oreochromis niloticus) were significantly affected by oxygen levels (1.5± 1.0, 2.8± 1.4, and 6.0± 1.8mg·L–1) in a controlled experiment designed to test the hypothesis (D. Pauly. 1984. J. Cons. Int. Explor. Mer, 41: 280–284) that O2 is the controlling factor for the transition from juvenile to adult in fish, in general, in the context of phenotypic life history plasticity and “stunting” in tilapias. Size at maturity and the estimated asymptotic size decreased with decreasing O2 concentration, as predicted by Pauly’s hypothesis. All fish matured at the same age (18weeks old), which is in contrast to conventional definitions of stunting. This finding challenges the suggested plasticity in age at first maturity for tilapia. The results also challenge the hypothesis that stunting is a unique recruitment mechanism, as the smaller fish in the group with low oxygen concentration produced smaller and fewer eggs than the larger fish in the group with high oxygen concentration.

La croissance, la taille à la maturité, l’indice gonadosomatique (GSI), la taille des œufs et la fécondité absolue du tilapia du Nil (Oreochromis niloticus) sont significativement affectés par les concentrations d’oxygène (1,5 ± 1,0; 2,8 ± 1,4; et 6,0 ± 1,8 mg·L–1) dans une expérience contrôlée visant à vérifier l’hypothèse (D. Pauly. 1984. J. Cons. Int. Explor. Mer, 41: 280–284) selon laquelle l’O2 est le facteur qui contrôle le passage du stade juvénile à l’adulte en général, dans le contexte de la plasticité phénotypique du cycle biologique et du «nanisme» chez les tilapias. La taille à la maturité et la taille estimée à l’asymptote sont toutes deux réduites dans les concentrations plus faibles d’O2, tel que le veut l’hypothèse de Pauly. Tous les poissons atteignent la maturité au même âge (18 semaines) contrairement aux définitions habituelles du nanisme. Cette observation met en doute la plasticité supposée de l’âge à la première maturité chez le tilapia. Nos résultats mettent aussi en doute l’hypothèse selon laquelle le nanisme est un mécanisme particulier du recrutement, car les poissons plus petits dans le groupe soumis aux faibles concentrations d’oxygène produisent des œufs plus petits et moins abondants que les poissons plus gros dans le groupe soumis aux fortes concentrations d’oxygène.

Document Type: Research Article

Publication date: July 1, 2008

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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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