Osmoregulation and growth in offspring of wild Atlantic salmon at different temperatures

In order to investigate how changes in gill Na+, K+-ATPase (NKA) alpha 1a, alpha 1b subunits, Na+, K+, 2Cl(-) cotransporter (NKCC1) and the apical cyctic fibrosis trans-membrane conductance regulator (CFTR-I) transcripts in wild Atlantic salmon, Salmo salar, smolts are affected by temperature during spring Atlantic salmon parr (initial mean length 12.8 cm, s.d. = 0.6, mean mass 22.1 g, s.d. = 3.2) originating from the Vosso river (western Norway) were reared under three temperature regimes (5.1, 8.1 and 10.8 A degrees C) from March to May. The temperatures reflect the natural temperature range in the study river during late spring. Findings from the present study indicate that smolt development differs within same strains held at different temperatures. Hence an absolute lower temperature limit for smolt development in wild salmon may be difficult to define. Overall present findings indicate that the smolt window will be narrower in warmer water. A temperature controlled smolt window may signify serious implications for smolt survival in wild (i.e., if migrants are delayed by obstacles or if hatchery produced smolts are released to late).