Environmental Biology of Fishes

, Volume 42, Issue 4, pp 401–412

Seasonal changes in hypoosmoregulatory ability in landlocked and anadromous populations of Arctic charr, Salvelinus alpinus, and Atlantic salmon, Salmo salar

  • Monika Schmitz

DOI: 10.1007/BF00001471

Cite this article as:
Schmitz, M. Environ Biol Fish (1995) 42: 401. doi:10.1007/BF00001471


Seasonal changes in hypoosmoregulatory ability were compared in landlocked and anadromous strains of Arctic charr and Atlantic salmon. Seawater adaptability was assessed using periodic 48 h seawater challenge tests with 25‰. seawater. The landlocked strains of Arctic charr, two from northern Sweden and one from Southern Norway, displayed similar seasonal changes in seawater adaptability as the anadromous strain. Seawater tolerance increased during spring and remained high until the end of July — early August after which it declined. The two strains of Atlantic salmon displayed different seasonal patterns in hypoosmoregulatory ability. The anadromous strain showed a pronounced seasonal pattern with maximal seawater adaptability in early June. In contrast, seawater tolerance in the landlocked strain improved steadily during spring and remained high until late autumn. During the period of enhanced seawater tolerance, hypoosmoregulatory ability increased significantly with body size in both Arctic charr and anadromous Atlantic salmon. The minimum size at which fish were able to regulate plasma sodium following seawater transfer at a level comparable to freshwater levels (<170 mmol I−1) differed significantly between anadromous Atlantic salmon (ca. 14 cm) and Arctic charr (ca. 22 cm). The results show that seasonal changes in hypoosmoregulatory ability are present in both Atlantic salmon and Arctic charr, and that these physiological traits are retained in the corresponding landlocked strains. However, the seasonal pattern of seawater adaptability as well as the minimum size at which seawater tolerance occurs differs between the two species.

Key words

Seawater adaptabilityMigrationDegree of anadromySalmonidaeFishes

Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • Monika Schmitz
    • 1
  1. 1.Department of AquacultureSwedish University of Agricultural SciencesUmeåSweden