| 1. |
- Arnason, T., et al.
(författare)
-
Long-term rearing of Arctic charr Salvelinus alpinus under different salinity regimes at constant temperature
- 2014
-
Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1145-1162
-
Tidskriftsartikel (refereegranskat)abstract
- Arctic charr Salvelinus alpinus of the Holar strain (mean+/- s. e. body mass= 152.1+/-3.1g) were reared at four different salinity regimes at a constant temperature of 7.4 degrees C. Two groups were given a three-month acclimation in salinity 18 before the salinity was increased to either 25 or 29 (groups called A25 and A29), and two groups were reared in salinities 25 or 29 over the full experimental period of 409 days (groups called F25 and F29). In the first 3months, the A25 and A29 groups had the highest growth rates. By October 2011, there were no significant differences (two-way nested ANOVA, P> 0.05) in the mean body masses among A25, F25 and F29 (c. 1450 g), whereas A29 had a lower mean mass (1282 g). The growth in the last period from October 2011 to January 2012 was reduced by sexual maturation in the highest salinity regimes (A29 and F29), whereas fish in groups A25 and F25 showed high growth throughout the study. Males in all salinity groups had higher growth rates than females for the most part of the study, but the divergence between the sexes was most pronounced in the highest salinity regimes. All salinity groups showed distinct changes in Na+, K+-ATPase activity, with high activity in spring and summer, and lower activity in the autumn. Plasma sodium (Na+) levels were stable indicating that none of the experimental groups had problems in maintaining hydromineral balance during the study. While plasma leptin levels were not affected by salinity regimes, it was noted that these levels were 13-30% higher in fish with empty guts compared with those having food in their gut at the time of sampling. This suggests a link between leptin levels and food intake, indicating that this hormone may play a role in food intake and energy allocation in fishes.
|
|
| 2. |
- Gunnarsson, S., et al.
(författare)
-
Effects of short-day treatment on long-term growth performance and maturation of farmed Arctic charr Salvelinus alpinus reared in brackish water
- 2014
-
Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1211-1226
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of a 6 week short-day photoperiod followed by continuous light, applied during the juvenile phase of Arctic charr Salvelinus alpinus in fresh water on smoltification and on the long-term growth andmaturity following transfer to brackish water (BW) (constant salinity of either 17 and 27 or increasing salinity in steps from 17 to 27) were investigated. Prior to salinity transfer, the juveniles were either reared at continuous light (C group) or reared for 6 weeks on a short day (8L: 16D, S group) followed by continuous light (24L: 0D). Increased salinity had negative effect on growth, with female fish reared at 17 salinity weighing 19 and 27% more than the salinity-step group (17-27) and the 27 salinity group, respectively. The stepwise acclimation to salinity had limited advantage in terms of growth rate. Short photoperiod for 6 weeks (November to January) followed by continuous light improved growth, but not seawater (SW) tolerance. Gill Na+, K+-ATPase activity and plasma Na+ levels changed with time, indicating some variation in osmoregulatory capacity during the experimental period. Overall, there appear to be interactive effects on maturation from applying short-day photoperiod followed by rearing at higher salinities. Plasma leptin varied with time and may be linked to stress caused by the observed variations in osmoregulatory ability. It is concluded that changes in growth rates observed in this study are mainly related to rearing salinity with higher growth rates at lower salinities. Short-day photoperiod has some growth-inducing effects but did not improve SW tolerance. Farmers of S. alpinus using BW for land-based rearing should keep salinity at moderate and stable levels according to these results to obtain best growth.
|
|
| 3. |
- Hailer, F., et al.
(författare)
-
Response to comment on "Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage"
- 2013
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 340:6127, s. 1522-b
-
Tidskriftsartikel (refereegranskat)abstract
- Nakagome et al. reanalyzed some of our data and assert that we cannot refute the mitochondrial DNA-based scenario for polar bear evolution. Their single-locus test statistic is strongly affected by introgression and incomplete lineage sorting, whereas our multilocus approaches are better suited to recover the true species relationships. Indeed, our sister-lineage model receives high support in a Bayesian model comparison.
|
|
| 4. |
- Otero, Jaime, et al.
(författare)
-
Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)
- 2014
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 20:1, s. 61-75
-
Tidskriftsartikel (refereegranskat)abstract
- Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.
|
|
| 5. |
- Arnason, Johann P., et al.
(författare)
-
Introduction
- 2013
-
Ingår i: The Greek Polis and the Invention of Democracy. - Chichester : Wiley-Blackwell. - 1444351060 ; , s. 1-18
-
Bokkapitel (refereegranskat)
|
|
| 6. |
- Arnason, T., et al.
(författare)
-
Effects of salinity and temperature on growth, plasma ions, cortisol and immune parameters of juvenile Atlantic cod (Gadus morhua)
- 2013
-
Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 380-383, s. 70-79
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of salinity and temperature on growth, plasma ions, cortisol and immune parameters were investigated in two experiments. In the first experiment small, medium and large juvenile Atlantic cod Gadus morhua (initial average weights of 1.9, 8 and 83 g, respectively) were reared at four constant salinities (6 to 32 parts per thousand) for a short period (19-57 days, depending on size), then returned to seawater (32 parts per thousand) without acclimation and reared for another period (20-391 days). The highest growth rates were found at 10 parts per thousand in all size-classes. After the fish were returned to seawater the growth rates were inversely related to the salinity change in all size-classes and long-term rearing of the medium-sized fish revealed that abrupt salinity increase from 6 and 10 parts per thousand to seawater may permanently reduce the growth capacity of juvenile cod. In another long-term experiment, there was no significant difference in the growth rate of cod (initial average weight 3.4 g) reared at either 13.5 or 32 parts per thousand for 187 days. Rearing at 13.5 parts per thousand neither enhanced growth rate at 6.3 degrees C nor at 10 degrees C in larger juveniles (>245 g) compared with rearing in seawater. The study shows that rearing salinity and abrupt salinity changes have limited or no effects on stress and immune-related parameters, and there are no indications of ion regulatory disturbances at salinities as low as 6 parts per thousand. This shows that the Atlantic cod is an extremely euryhaline marine teleost species, and indicates that commercial Atlantic cod aquaculture can just as well be carried out in locations with low as with high environmental salinity. (C) 2012 Published by Elsevier B.V.
|
|
| 7. |
- Hailer, Frank, et al.
(författare)
-
Nuclear Genomic Sequences Reveal that Polar Bears Are an Old and Distinct Bear Lineage
- 2012
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 336:6079, s. 344-347
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown that the polar bear matriline (mitochondrial DNA) evolved from a brown bear lineage since the late Pleistocene, potentially indicating rapid speciation and adaption to arctic conditions. Here, we present a high-resolution data set from multiple independent loci across the nuclear genomes of a broad sample of polar, brown, and black bears. Bayesian coalescent analyses place polar bears outside the brown bear clade and date the divergence much earlier, in the middle Pleistocene, about 600 (338 to 934) thousand years ago. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial DNA due to past hybridization. Our results highlight that multilocus genomic analyses are crucial for an accurate understanding of evolutionary history.
|
|
| 8. |
|
|
| 9. |
|
|
