Hypoxia Turbot

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Journal of Fish Biology October 2001; 59 (4) : 875 - 883 http://10.1111/j.1095-8649.2001.tb00158.x © 2001 Blackwell Publishing, Inc.
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Comparative effects of long-term hypoxia on growth, feeding and oxygen consumption in juvenile turbot and European sea bass
K. Pichavant*1, J. Person-Le-Ruyet1, N. Le Bayon1, A. Severe1, A. Le Roux1 and G. Boeuf1, 2

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Laboratoire Adaptation, Reproduction and Nutrition, Ifremer, Centre de Brest, BP 70, 29280Plouzane, France

Present address: Laboratoire Arago, Observatoire Océanologique, CNRS/Université Pierre et Marie Curie, 66651 Banyuls-sur-mer, France.

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*Author to whom correspondence should be addressed at present address: Laboratoire de Biologie et Physiologie Cellulaires, UFR Sciences et Techniques, Université de Bretagne occidentale, 6 avenue Le Gorgeu, BP 809 29285 Brest Cédez,France. Tel.: +33 02 98 01 72 60; fax: 33 02 98 01 63 11; email: Karine.Pichavant@univbrest.fr.

Abstract: When juvenile turbot Scophthalmus maximus and sea bass Dicentrarchus labrax were fed to satiation, growth and food intake were depressed under hypoxia (3·2±0·3 and 4·5±0·2 mg O2 l-1). However, no significant difference in growth was observed between fishes maintained in hypoxia and fed tosatiation and fishes reared in normoxia (7·4±0·3 mg O2 l-1) and fed restricted rations (same food intake of fishes at 3·2 mg O2 l-1). Routine oxygen consumption of fishes fed to satiation was higher in normoxia than in hypoxia due to the decrease in food intake in the latter. Of the physiological parameters measured, no significant changes were observed in the two species maintained in hypoxia. Thisstudy confirms the significant interaction between environmental oxygen concentrations, feeding and growth in fishes. Decrease in food intake could be an indirect mechanism by which prolonged hypoxia reduces growth in turbot and sea bass, and may be a way to reduce energy and thus oxygen demand. Keywords: turbot; sea bass; hypoxia; growth; oxygen consumption

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INTRODUCTION Acute decreasesin water oxygen (O2) concentrations may occur in intensive fish farming, especially when fishes are reared at high densities. Considerable attention has been paid to oxygen, as low ambient O2 concentrations are known to affect growth, food consumption and physiological state of fishes (Jobling, 1994). O2 levels at which the decrease in growth is observed vary according to the species. In coho,Oncorhynchus kisutch (Walbaum) and sockeye salmon O. nerka (Walbaum), largemouth bass Micropterus salmoides (Lacépède) and carp Cyprinus carpio (L.), growth is afffected by O2 concentrations < 4-5 mg l-1 (Brett, 1979; Brett & Blackburn, 1981). In rainbow trout, O. mykiss (Walbaum), the O2 concentration threshold for growth is much higher, 7 mg l-1 (Pedersen, 1987). Most of the studies on therelationship between O2 and growth have been conducted on freshwater fish species. The present study was undertaken to examine the interactions between oxygen availability and growth in two, economically important, marine fishes, turbot Scophthalmus maximus (L.) and sea bass Dicentrarchus labrax (L.). In a previous study (Pichavant et al., 2000), it was shown that in juvenile turbot growth was reducedwhen these fishes were maintained in hypoxic water (5.0 mg O2 l-1). It was hypothesized that one of the mechanisms by which long-term hypoxia reduced growth in juvenile turbot was a decrease in food intake. This hypothesis is tested in the present study.

MATERIALS AND METHODS FISH AND EXPERIMENTAL DESIGN Experiments were carried out with 6 to 8 month old hatchery-reared juvenile turbot and sea...