### Name

Sigurd Olav Stefansson

On sabbatical leave from University of Bergen until August 2004

### Permanent address

Department of Fisheries and Marine Biology

University of Bergen

P.O. Box 7800

N-5020 Bergen

NORWAY

### Research interests, motivation

Main topics: Salmon biology with particular focus on smoltification
(parr-smolt transformation), fish physiology and endocrinology, fish
reproduction and growth.

In studies of salmon smoltification my main objective has been to better
understand the environmental and endocrine control of the development of
hypo-osmoregulatory ability. Further, much of my work in recent years
has been focusing on genetic x environment interactions controlling
growth and puberty (age at first sexual maturity) in fish species like
salmon, turbot, halibut and cod.

In my studies I have tried to combine a basic approach to general
biological questions with species and processes of major interest in
nature and culture.

### Selected recent publications (2001 -- present)

Handeland, S. O. and S. O. Stefansson, 2001. Photoperiod control and
influence of body size on off-season parr-smolt transformation and
post-smolt growth. *Aquaculture* **192**, 291-307.

Handeland, S. O. and **S. O. Stefansson**, 2002. Effects of salinity
acclimation on pre-smolt growth, smolting and post-smolt performance in
off-season Atlantic salmon smolts *(Salmo salar* L.). *Aquaculture*
**209**, 125-137.

Imsland, A. K., T. M. Jonassen, R. Hoare, A. Langston, H. Wergeland, R.
FitzGerald, M. Mulcahy and **S. O. Stefansson**, 2002. The interrelation
of growth and disease resistance of different populations of juvenile
Atlantic halibut (*Hippoglossus hippoglossus* L.). *Aquaculture*
**204**, 167-177.

Imsland, A. K., A. Foss, S. Gunnarsson, M. H. G. Berntssen, R.
FitzGerald, S. E. Wendelar-Bonga, E. van Ham, G. Nævdal and **S. O.
Stefansson**, 2001. The interaction of temperature and salinity on
growth and food conversion in juvenile turbot (*Scophthalmus maximus*).
*Aquaculture* **198**, 353-367.

Imsland, A.K., A. Foss, B. Sveinsbø, T. M. Jonassen and **S. O.
Stefansson**, 2001. Comparisons of RNA/DNA ratios, growth and metabolism
of different populations of juvenile turbot *Scophthalmus maximus*
reared at four temperatures. *J. World Aqua. Soc*. **32**, 1-10.

Imsland, A. K., A. Foss, G. Nævdal and **S. O. Stefansson**, 2001.
Selection or adaptation: differences in growth performance of juvenile
turbot (*Scophthalmus maximus* Rafinesque) from two close-by localities
off Norway. *Sarsia* **86**, 43-51.

Porter, M. J. R., N. Duncan, S. O. Handeland, **S. O. Stefansson** and
N. R. Bromage, 2001. Temperature, light intensity and plasma melatonin
levels in juvenile Atlantic salmon. *J. Fish. Biol.* **58**, 431-438.

Andersson, E., Fjelldal, P. G., Klenke, U., Vikingstad, E, Taranger, G.
L., Zohar, Y. and **Stefansson, S. O.**, 2001. Three forms of GnRH in
the brain and pituitary of the turbot, *Scophthalmus maximus*:
immunological characterization and seasonal variation. *Comp. Biochem.
Physiol.* **129**, 551-558.

Hoare, R., H. Hovland, A. L. Langston, A. K. Imsland, **S. O.
Stefansson,** M. Mulcahy and H. I. Wergeland, 2002. Susceptibility of
three different strains of juvenile Atlantic halibut (*Hippoglossus
hippoglossus* L.) cultured at two different temperatures to *Vibrio
anguillarum* and temperature effect on antibody response. *Fish
Shellfish Immunol*. **13**, 111-123.

Andreassen, P. M.R., M. B. Martinussen, N. A. Hvidsten and **S. O.
Stefansson**, 2001. Feeding and prey-selection of wild Atlantic salmon
post-smolts. *J. Fish Biol*. **58**, 1667-1679.

Imsland, A. K., A. Foss and **S. O. Stefansson**, 2001. Variation in
food intake, food conversion efficiency and growth of juvenile turbot
from different geographic strains. J. Fish Biol. **59**, 449-454.

Ebbesson, L. O. E., P. Ekström, S. O. E. Ebbesson, **S. O. Stefansson**
and B. Holmqvist, 2003. Neural circuits and their structural and
chemical reorganization in the light-brain-pituitary axis during
parr-smolt transformation in salmon. *Aquaculture* **222**, 59-70.

Arnesen, A. M., H. Toften, T. Agustsson, **S. O. Stefansson**, S. O.
Handeland and B. Th. Björnsson, 2003. Osmoregulation, feed intake,
growth and growth hormone levels in 0+ Atlantic salmon (*Salmo salar*
L.) transferred to seawater at different stages of development.
*Aquaculture* **222**, 167-187.

Nilsen, T. O., L. O. E. Ebbesson and **S. O. Stefansson**, 2003.
Smolting in anadromous and landlocked strains of Atlantic salmon (*Salmo
salar*). *Aquaculture* **222**, 71-82.

Imsland, A. K., A. Foss, S. W. Bonga, E. van Ham and **S. O.
Stefansson**, 2002. Comparison of growth and RNA:DNA ratios in three
populations of juvenile turbot reared at two salinities. *J. Fish Biol.*
**60**, 288-300.

Fivelstad, S., A. B. Olsen, T. Åsgård, G. Bæverfjord, T. Rasmussen, T.
Vindheim and **S. O. Stefansson**, 2002a. Long-term sublethal effects of
carbon dioxide on Atlantic salmon smolts (*Salmo salar* L.): ion
regulation, haematology, element composition, nephrocalcinosis and
growth parameters. *Aquaculture* **215**, 301-319.

Fivelstad, S., R. Waagbø, S. F. Zeitz, A. C. D. Hosfeld, A. B. Olsen and
**S. O. Stefansson**, 2002b. A major water quality problems in smolt
farms: combined effects of carbon dioxide, reduced ph and aluminium on
Atlantic salmon (Salmo salar L.) smolts: physiology and growth.
*Aquaculture* **215**, 339-357.

Handeland, S. O., B. Th. Björnsson and **S. O. Stefansson**, 2003.
Seawater adaptation and growth of post-smolt Atlantic salmon (*Salmo
salar* L.) of wild and farmed strains. *Aquaculture* **220**, 367-384.

van Ham, E. H., M. H. G. Berntssen, A. K. Imsland, A. C. Parpoura, S. E.
Wendelaar Bonga and **S. O. Stefansson**, 2003. The influence of
temperature and ration on growth, feed conversion, body composition and
nutrient retention of juvenile turbot (*Scophthalmus maximus*).
*Aquaculture* **217**, 547-558.

**Stefansson, S. O.**, P. McGinnity, B. Th. Björnsson, C. Schreck, S. D.
McCormick, 2003. The importance of smolt development to salmon
conservation, culture, and management: perspectives from the 6th
International Workshop on Salmonid Smoltification. *Aquaculture*
**222**, 1-14.

Handeland, S. O., M. Porter, B. Th. Björnsson and **S. O. Stefansson**,
2003. Osmoregulation and growth in a wild and selected strain of
Atlantic salmon smolts on two photoperiod regimes. *Aquaculture*
**222**, 29-43.

Imsland, A. K., S. Gunnarsson, A. Foss and **S. O. Stefansson**, 2003.
Gill Na^+^,K^+^-ATPase, plasma chloride and osmolality in juvenile
turbot (*Scophthalmus maximus*) reared at different temperatures and
salinities. *Aquaculture* **218**, 671-683.

Imsland, A. K., M. Dragsnes and **S. O. Stefansson**, 2003. Exposure to
continuous light inhibits maturation in turbot (*Scophthalmus maximus*).
*Aquaculture* **219**, 911-919.

Handeland, S. O., E. Wilkinson, B. Sveinsbø, S. D. McCormick and **S. O.
Stefansson**, 2003. Temperature influence on the development and loss of
seawater tolerance in two fast-growing strains of Atlantic salmon.
*Aquaculture* **00**, 000-000.

**Stefansson**, **S. O.**, B. Th. Björnsson, K. Sundell, G. Nyhammer and
S. D. McCormick, 2003. Physiological characteristics of wild Atlantic
salmon post-smolts during estuarine and coastal migration. *J. Fish
Biol*. **63**, 942-955.

Ebbesson, L. O. E., C. K. Tipsmark, B. Holmqvist, T. O. Nilsen, E.
Andersson, **S. O.** **Stefansson** and S. S. Madsen, 2003. Nitric oxide
synthase in the gill of Atlantic salmon: co-localization with and
inhibition of the Na^+^,K^+^-ATPase. *J. Exp. Biol.* (in revision).

Taranger, G. L., E. Vikingstad, U. Klenke, I. Mayer, **S. O.
Stefansson**, B. Norberg, T. Hansen, Y. Zohar and E. Andersson, 2003.
Effects of photoperiod, temperature and GnRHa treatment on the
reproductive physiology of Atlantic salmon (*Salmo salar*) broodstock.
*Fish Physiol. Biochem.* (in revision).

van Ham, E. H., R. D. Van Anholt, G. Kruitwagen, A. K. Imsland, A. Foss,
B. O. Sveinsbø, R. FitzGerald, A. C. Parpoura, **S. O. Stefansson** and
S. E. Wendelaar Bonga, 2003. Environment affects stress in exercised
turbot. *Comp. Biochem. Physiol*., **000**, 000-000.