SEAWATER ACCLIMATION OF DIPLOID AND TRIPLOID BROOK CHARR (SALVELINUS-FONTINALIS), DIPLOID ARCTIC CHARR (SALVELINUS-ALPINUS), AND THEIR DIPLOID AND TRIPLOID HYBRIDS

Seawater acclimation of diploid (FF) and triploid (F2F) brook charr Salvelinus fontinalis, diploid (AA) Arctic charr Salvelinus alpinus, and diploid (FA) and triploid (F2A) hybrids between female brook charr and male Arctic charr was investigated. Triploidization of brook charr and the hybrid did not have any effect on the acclimation. Seawater acclimation of the hybrid was achieved during the experimental period and was comparable to that observed in brook charr. Acclimation could not be ascertained in Arctic charr since the level of cortisol. a stress indicator, was still high at the end of the experiment. No relationship between either length or condition factors and plasma osmolality was observed. Elevated plasma cortisol concentrations in Arctic charr and in diploid or triploid hybrids, both in fresh water and sea water, indicate more favourable rearing conditions for brook charr.