Effects of salinity on the ionic balance and growth of juvenile turbot

Abstract

The effects of salinity changes (27, 19 and 10%~)) on seawater-adapted juvenile turbot were studied on their plasma osmolarity aiid ion concentrations, on oxygen consumption, on gill Na',K'-ATPase activity after 3 months and on growth parameters. All plasma concentrations (except chloride) were unchanged, suggesting that fish were well adapted to their environment. Oxygen consumption was significantly decreased in the 19 and 10%0 groups, where fish weighed significantly more 105 days after transfer than fish maintained in sea water. These results, and the fact that apparent food conversion rates were iower in a diluted environment, suggest that on a long term schedule growth conditions could be improved by adaptation to brackish waters (salinities between 10 and 19%). The effects of transfer from sea water to 27, 19, 10 and 5% were also followed during the first 3 weeks. With salinity 10% a steady state was reached on day 21 with all plasma values within the same range. The significant differences observed in osmolarity, plasma ion concentrations and Na+,K+-ATPase activity 3 weeks after transfer of juveniles to 5%n salinity, compared with transfers in higher salinities, suggest that there is B threshold of acclimation of turbot to a hypotonic environment. 3: ) 1995 The Fisheries Society uf the British Isles

Capacités adaptatives du turbot (Psetta maxima) juvénile à la photopériode

“…Dans le cadre d'expériences, menées antérieurement dans notre laboratoire, avec une souche de turbot du proche-Atlantique stabulée depuis quelques années au centre IFREMER de Brest, les limites de son « confort physiologique » ont été précisées en faisant varier la salinité (GAUMET et al, 1995) et la température (BUREL et al, 1996). Cette expérience sur la photopériode, menée dans les mêmes conditions, permet de compléter ces travaux.…”

“…Nous pouvons citer entre autres les données de KÙHLMANN et QUANTZ (1980), WALLER (1992) sur la salinité ; JONES et al (1981), IGLESIAS et al (1987), PERSON-Le RUYET et al (1991) sur la température et IMSLAND et al (1995) sur la photopériode. Les travaux prenant réellement en compte les relations entre les données zootechniques et les réponses physiologiques du turbot, estimées par l'utilisation de divers indicateurs spécifiques, sont relativement récents : travaux de BUREL et al (1996) sur la température et de GAUMET et al (1995) sur la salinité. Afin de déterminer les conditions ambiantes optimales au « confort physiologique » et à la meilleure expression possible de la croissance de cette espèce, l'impact de la photopériode restait à préciser.…”

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

“…On sampling and weighing dates, no hypoxic shock was applied to fish. The O 2 concentrations in each tank of the 100-20 and 75-20 groups were monitored when hypoxic shocks were applied (four measurements per hour and per tank) according to a method adapted from Gaumet et al (1995). Ambient pH and ammonia were monitored at 5-d intervals.…”

Current growth, fat reserves and somatic condition of juvenile Baltic herring (Clupea harengus membras) reared in different salinities

“…Alternatively, faster growth can be a result of decreased costs of osmoregulation (Hettler 1976;Imsland et al 2003). For instance in turbot, growth was improved when fish were reared in water that was isoosmotic to fish blood (Gaumet et al 1995;Imsland et al 2003). In our study, a direct effect of salinity on growth was obvious, although this effect may well have been strengthened by lower costs of osmoregulation in the higher salinities.…”