| Summary: | Groups of Arctic char (Salvelinus alpinus) were reared under three experimental light regimes. Two different strains of char were used, one non-migratory from south Norway, the other anadromous from northern Norway. All groups received a continous background illumination. One of the experimental light regimes consisted only of this background illumination. The remaining two treatments consisted of an additional simulated natural photoperiod, using either yellow light or daylight. Growth rate was monitored during the experiment. A Seawater Challenge Test (SWCT) was run for 24 hours to evaluate the ability of the two strains of char to tolerate and survive in seawater. There were no significant differences in growth rate in either strain between the experimental light regimes. Condition factor increased during the experimental period for fish of both strains and all light regimes. Both strains tolerated the SWCT without mortalities. Size seems to be the most important factor for seawater adaptability of Arctic char. There were no signs of a smoltification process as seen in Atlantic salmon (Salmo salar).
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