ADVANCING SMOLTING TO AUTUMN IN AGE 0-TERM PERFORMANCE IN SEA-WATER( ATLANTIC SALMON BY PHOTOPERIOD, AND LONG)

Citation
J. Duston et Rl. Saunders, ADVANCING SMOLTING TO AUTUMN IN AGE 0-TERM PERFORMANCE IN SEA-WATER( ATLANTIC SALMON BY PHOTOPERIOD, AND LONG), Aquaculture, 135(4), 1995, pp. 295-309
Citations number
52
Categorie Soggetti
Fisheries,"Marine & Freshwater Biology
Journal title
ISSN journal
00448486
Volume
135
Issue
4
Year of publication
1995
Pages
295 - 309
Database
ISI
SICI code
0044-8486(1995)135:4<295:ASTAIA>2.0.ZU;2-3
Abstract
Smelting in autumn in age 0 + Salmo salar was improved by 2 months of short photoperiod in an otherwise constant long photoperiod regime. Fo ur groups of fry were reared under either constant-long photoperiod (L D 17:7), or LD17:7 interrupted by LD7:17 for one (Imo-short; July 27-S eptember 1) or 2 months (2mo-short; June 30-September 1), or simulated natural day length (LDN). Bimodality in size-frequency developed in a ll groups by August. Probability of an individual entering the upper-m odal group (UMG) was related positively to fork length in late June. T he LDN regime had the highest proportion of both lower-modal group fis h (46% vs. 25-27%), and 0 + sexually mature males of the four groups ( 26% vs. 10-12%). Smelt development in autumn was highest in the 2mo-sh ort group, but was inferior to normal spring smelts, as judged by hypo osmoregulatory ability and gill Na+ K+ ATPase activity. Following tran sfer of UMG fish to a sea-cage in November, the 2mo-short group exhibi ted best survival and growth over winter. From spring onwards all grou ps grew well, reaching harvest size (3-4 kg) in August after 20 months in sea water. Mortality in sea water was 24% and 28% in the 2mo- and 1mo-short groups, and 54% and 67% in the constant-long and LDN groups, The study indicated the feasibility of stabilising the undesirable se asonal fluctuation in commercial salmon production by producing 'off-s eason' smolts 6 months out-of-phase from regular spring smelts.