Seasonal changes in sea-water tolerance of Arctic charr (Salvelinus alpinus)

Sexually immature two-year old Arctic char (Salvelinus alpinus) were implanted with Silastic capsules containing testosterone or 11-ketoandrostenedione in early spring. Seawater adaptability of the hormone-treated and sham-operated fish was tested periodically from May to August using a 48h seawater challenge test with 25‰ seawater. The sham-operated control fish displayed a seasonal pattern in seawater adaptation, showing a good hypoosmoregulatory ability until mid June followed by a marked increase in plasma sodium and magnesium levels in July and August. Gill Na(+)-K(+)-ATPase activity decreased concurrently with the observed decrease in seawater adaptability. Over the same period the androgen-treated fish displayed a similar pattern in seawater adaptability, however, in May and June the plasma sodium levels were significantly higher in both androgen-treated groups compared to the control group. Plasma magnesium regulation was impaired in both androgen-treated groups in August. Gill Na(+)-K(+)-ATPase activity in the testosterone-treated fish was lower in June compared to the control fish, whereas the activity was not affected by 11-ketoandrostenedione treatment. The results show that while androgens impair the hypoosmoregulatory capacity in Arctic char, the seasonal pattern of seawater adaptability is not affected.

Section: Discussionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of androgens on seawater adaptation in Arctic char, Salvelinus alpinus

Schmitz

Mayer

1993

“…For instance, in Atlantic salmon, plasma osmolality increased from 320 to 440 mOsm kg I as temperature decreased from 3 to 5.6°C to 2 to 1 °C (Lega et al 1992). The ability of fish to osmoregulate is also affected by photoperiod (Dustan and Knox 1992) and season of the year (Finstad et al 1989b;Arnold-Reed and Balment 1991).…”

Section: Introductionmentioning

confidence: 99%

Effects of salinity on the growth and lipid composition of Atlantic salmon (Salmo salar) and turbot (Scophthalmus maximus) cells in culture

Tocher

Castell

Dick

et al. 1994

The direct effects of osmotic pressure (salinity) on growth performance and lipid composition were investigated in fish cells in culture. Cell lines from a relatively stenohaline marine species, turbot (Scophthalmus maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce osmotic pressures varying from 300 to 500 mOsm kg(-1). The growth rates of the two cell lines were affected in a similar manner by the salinity of the media with the rank order for both peak cell numbers and growth rates up to the day of peak cell number being 300 > 350 > 400 > 450 > 500 mOsm kg(-1). Cell death occurred in both cell lines in older cultures at all salinities with the greatest loss of viable cells in media of 300 and 350 kg(-1). However, there were quantitative and qualitative differences between the cell lines in their lipid metabolism in response to the salinity of the media. The lipid content expressed per cell showed a positive correlation between lipid per cell and salinity in TF cells, but this was less apparent in AS cells. The percentage of total polar lipid classes increased with increasing salinity in TF cells due mainly to graded increases in the percentages of choline phospholipids. In contrast, there were no significant differences in the proportions of polar and neutral lipid classes with salinity in AS cells. The only significant effect of salinity in AS cells was a decreased proportion of dimethylacetals in total lipid at the highest salinity. The same significant effect of salinity on dimethylacetal content of total lipid was observed in TF cells. However, in addition there was a graded decrease in the percentage of 18:2n-9 in TF cell total lipid with increasing salinity. This was accompanied by increased percentages of total n-3 and n-6 PUFA with higher proportions of both groups of PUFA at 450 and 500 compared with 300 mOsm kg(-1). The results show that environmental salinity, in the absence of hormonal or other physiological stimuli, has direct effects on the growth and lipid metabolism of fish cells and that these effects differ in cells from different fish species.

“…Overwintering mortalities in the sea have been quite variable, but in some cases have been reported to be as high as 60-100% (Gjedrem 1975;Gjedrem and Gunnes 1978;Wandsvik and Jobling 1982). The poor performance in seawater during winter has been related to seasonal changes in seawater tolerance (Finstad et al 1989). …”

Section: Introductionmentioning

confidence: 99%

Feed intake, growth and osmoregulation in Arctic charr, Salvelinus alpinus (L.), transferred from freshwater to saltwater at 8°C during summer and winter

Arnesen

Jørgensen

Jobling

1993

Self Cite

The purpose of the current study was to examine seasonal changes in seawater tolerance and growth performance of anadromous Arctic charr (Salvelinus alpinus L.) held at the same temperature (8°C) during winter and summer. Charr (20-27 cm), previously reared in freshwater under natural photoperiod, were transferred either directly (DT) from freshwater to seawater (35 ppt), from freshwater to brackish water (20 ppt), or were gradually adapted (GT) to seawater over a period of 10 days. Control fish were held in freshwater. Feed intake and osmoregulatory ability were then monitored on three occasions during the following 59 days. Two experiments were carried out, one during winter (December-January) and the other during summer (June-July). In both experiments fish mortality was low. Plasma osmolalities recorded in fish transferred to seawater were within normal ranges, but osmolalities on day 10, were significantly lower in summer (313 mOsm/kg (DT), 328 mOsm/kg (GT)) than in winter (323 mOsm/kg (DT), 352 mOsm/kg (GT)). In winter, feed intake and growth rates were high in fish kept in fresh and brackish water, but charr transferred directly to seawater ate little and lost weight. Fish that were gradually adapted to seawater occupied an intermediate position. During summer the observed differences in feed intake were small and all fish had relatively high growth rates. These results suggest that Arctic charr display seasonal changes in feed intake and growth performance that parallel seasonal changes in hypoosmoregulatory capacity. The ability to survive and hypoosmoregulate in full strength seawater does not, however, seem to be a particularly good indicator of successful seawater adaptation with respect to the ability to display high rates of feed intake and growth. During winter, a gradual transfer to seawater appeared to lead to improved feeding and growth compared to direct transfer.