Effects of repeated hypoxic shocks on growth and metabolism of turbot juveniles

Abstract

Turbot juveniles (45 g) were exposed for 41 d (17°C, 34‰ salinity) to constant normoxic (100-100% air saturation, 100-100) or moderate hypoxic (75-75% air saturation, 75-75) conditions and to repeated hypoxic shocks (20% saturation for 1 h, 5 d per week) from normoxic (100-20% air saturation, 100-20) or moderate hypoxic (75-20% air saturation, 75-20) conditions. A normoxic group was feed restricted (100-FR). Mass increase of 100-100 and 75-75 groups fed to satiation was not significantly different. In comparison, it was significantly lower in the 100-20 and 75-20 groups (NS between the two hypoxic shocks groups). Intermediate results were obtained in the 100-100-FR group. The lowest mass increase under hypoxic shocks was explained by a significant decrease in both feed intake and food conversion efficiency (FCE). FCE was lower in the two hypoxic groups, but only the 75-20 group was significantly different from all the other groups. There was no sign of stress and no change in the physiological status of fish in any group. When challenged, pre-conditioning of turbot to regular hypoxic shocks extended survival time, slightly but significantly, for 50% of the population. It was 8 h longer in starved than in fed fish. When reared for 1 year in normoxic water, the growth rate of post-challenged survivors was dependent on pre-conditioning: day 0-375 specific growth rate was significantly higher in the two groups acclimated to repeated hypoxic shocks. In the second experiment, it was shown that exposure to 20% air saturation for 12 h led to major physiological changes within 4 h: a significant decrease in plasma total CO 2 and increase in plasma lactate contributing in maintaining blood pH stable, and a significant increase in osmolarity and chloride concentration. When returned to normoxic water, the recovery capacity of the fish was high: plasma osmolarity and total CO 2 returned to pre-exposure levels within 1 h. The results are discussed in terms of turbot capacity to cope with repeated hypoxic shocks and to acclimate. RésuméEffets de chocs hypoxiques répétés sur la croissance et le métabolisme du turbot juvénile. Des turbots (45 g) ont été élévés pendant 41 jours (17°C, et 34 salinité) en normoxie (100-100 % de la saturation) ou hypoxie modérée (75-75), ou soumis à des chocs hypoxiques de 20 % de la saturation pendant une heure 5 fois par semaine (100-20 et 75-20). Un lot en normoxie reçoit la ration alimentaire du lot 100-20 (100-R). La croissance pondérale n'a pas été perturbée par l'hypoxie modérée à niveau constant mais l'a été par les chocs hypoxiques répétés. La baisse de croissance observée résulte d'un effet cumulé d'une baisse de l'appétit et d'une diminution de l'efficacité alimentaire (lot 75-20 significativement différent des autres lots). Aucune modification de l'état physiologique n'a été mise en évidence (absence de stress). Une mise à l'épreuve en fin d'expérience (20 % de la saturation) a montré qu'un préconditionnement à différentes conditions d'oxygénation a un effet bénéfique faible ma...

Effects of chemical stress and food limitation on the energy reserves and growth of turbot, Scophthalmus maximus

“…It consists of faster fish growth following a period of growth depression as compared to their normally growing counterparts (Sevgili et al 2012). In fish, CG can be elicited through a number of ways such as starvation, feed restriction, exposure to low or high temperature and hypoxia (Eroldoğan et al 2006;Hayward et al 1997;Huang et al 2008;Miglavs and Jobling 1989;Person-Le Ruyet et al 2003). As observed in the present study, CG was more frequent with fish weight than fish length.…”

Narragansett Bay Hypoxic Event Characteristics Based on Fixed-Site Monitoring Network Time Series: Intermittency, Geographic Distribution, Spatial Synchronicity, and Interannual Variability

“…5) and T 1.4 (Fig. 7), as well as results of the MWT algorithm applied to all sites and all years using lower threshold and shorter minimum event duration values (0.5 mg O 2 l −1 and 4 h; trigger duration 2 h) as justified in the "Introduction" (Rosenberg et al 1991;Sagasti et al 2001;Wu 2002;Person-LeRuyet et al 2003;Vaquer-Sunyer and Duarte 2008). Such more intense and shorter events occurred only at GB (18, 3, and 11 events in 2003GB (18, 3, and 11 events in , 2005GB (18, 3, and 11 events in , and 2006, respectively), MV (eight events in 2006), and NP (two and one event, in 2003 and 2006, respectively).…”

“…Taxonomic rankings indicate that fishes and crustaceans show greatest sensitivity, followed by echinoderms, while annelids and especially cnidarians and molluscs tend to show greatest tolerance (Diaz and Rosenberg 1995;Gray et al 2002;Vaquer-Sunyer and Duarte 2008). The highest risk of direct mortality occurs at concentrations of 0.5 to 1.0 mg O 2 l −1 for many moderately sensitive species and at 1.0 to 2.0 mg O 2 l −1 for many sensitive species, with mortality often taking place within the first 4 to 7 h; for highly tolerant benthic infaunal species, risk requires more severe conditions (≤0.5 mg O 2 l −1 ) of greater duration (days to weeks; Rosenberg et al 1991;Sagasti et al 2001;Wu 2002;Person-LeRuyet et al 2003;Vaquer-Sunyer and Duarte 2008). Larvae are generally more acutely sensitive than juveniles and adults (USEPA 2000); Rhode Island (RI) water quality regulations, designed for protection of larvae, treat a 1-day exposure to 2.9 mg O 2 l −1 as a violation (RIDEM 2006).…”

The effect of intermittent hypoxia on growth, appetite and some aspects of the immune response of Atlantic salmon (Salmo salar)

“…However, it is unclear how these conditions might affect the growth and physiology of these fish because of the different methodologies used by previous authors, differences in the degree of hypoxia tolerance between species (Vanquer‐Sunyer & Duarte ) and the variable endpoints reported. Person‐Le Ruyet, Lacut, Le Bayon, Le Roux, Pichavant and Quéméner () exposed juvenile turbot [ Scophthalmus maximus (Waite 1910)] held under either normoxic (7.4 mg O 2 L −1 ) or moderate hypoxic (6.0 mg O 2 L −1 ) conditions to repeated hypoxic shocks (1.5 mg O 2 L −1 , 5 per week for 1 h) and showed significant reductions in growth (a 14.9% reduction in mass gain). Taylor and Miller () found that the growth rate of southern flounder [ Paralichthys lethostigma (Jordan & Gilbert 1884)] was reduced by 22.9% when they were exposed to episodic hypoxia (2.8–6.2 mg O 2 L −1 ) for 21 days.…”