Summer osmoregulatory capacity of the worlds northernmost living
salmonid.
Nilssen, Kjell J., Odd A. Gulseth, Martin Iversen, and Roar
Kj[stod]ol.
Bratt[stod]ora Research Center, Department of Zoology, Norwegian
University of Science and Technology, N- 7034, Trondheim, Norway,
Norwegian Polar Institute, N-0368 Oslo, Norway
APStracts 3:0368R, 1996.
Anadromous Arctic charr (Salvelinus alpinus L.) were caught on their
way to and from the sea by use of a fish trap placed in the Dieset
watercourse located on the Spitsbergen Island (79 degrees 10' NL),
within the high-Arctic Svalbard archipelago. When subjected to a
seawater challenge test (34 ppt. at 4 to 5 degrees C), charr on their
way to the sea showed only minor and temporary changes in blood
plasma osmolality and Na+ and Mg2+ concentrations. The seawater tests
also revealed good hypoosmoregulatory capacity for Arctic charr
returning from the marine environment 4 weeks later. A progressive
decrease in seawater tolerance was first documented 7 to 11 days
after their return to the freshwater habitat. Thus, the Svalbard
charr being the northernmost anadromous salmonid, and probably a
direct descendant from the first Salvelinus immigrants to freshwater
systems, undergoes a preparatory increase of hypoosmoregulatory
capacity (smoltification) before entering the oceanic waterbodies.
Furthermore, the termination of their short annual seawater stay is
probably elicited by factors controlling body systems other than
osmoregulation.
Received 3 June 1996; accepted in final form 17 September 1996.
APS Manuscript Number R307-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996