Ma. Thrush et al., THE USE OF PHOTOPERIOD IN THE PRODUCTION OF OUT-OF-SEASON ATLANTIC SALMON (SALMO-SALAR) SMOLTS, Aquaculture, 121(1-3), 1994, pp. 29-44
Accelerated seasonally-changing and ''square-wave'' (direct change fro
m short to long day) photoperiods advanced the timing of potential S1
(1+) and S2 (2+) smolts by a maximum of 3 and 7 months respectively. P
re-smolts underwent body silvering, fin darkening and a decrease in co
ndition factor in response to changes from short to long day-lengths.
Seawater challenge (24 h, 28 ppt) tests showed these fish to develop s
trong hypo-osmoregulatory ability. Smolts were transferred to full str
ength seawater in small land-based facilities and to commercial on-gro
wing sites. S1 groups, which were advanced by up to 3 months, gained a
growth advantage from early seawater transfer that was maintained thr
oughout their first year in seawater. Potential S2 smolts transferred
in October-November grew well over their first winter. Advanced mixed
sex S1s did not show any post-smolt maturation, but did show increased
rates of maturation (up to 19%) after one winter at sea. Advanced S2
smolts showed an increased post-smolt maturation.