Delayed photoperiod induces increased seapen survival, increased growth rate and increased uniformity of size of coho salmon (Oncorhynchus kisutch) transferred into seawater at age 0+, under intensive culture conditions
Date
1989
Authors
Corley-Smith, Graham Edmund
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The effect of delayed photoperiod on coho salmon fry first fed as late as March and April and transferred to seapens in their first summer, was measured by survival and growth rates. In 1987 , three lots of fry, progeny of wild broodstock, were first fed as follows: lots 1 and 2 from Robertson Creek (49°20'N, 124°59'W} on 3 and 17 March respectively, and lot 3 from Kitimat (54°7 1 N, 128°38 1 W} on 12 April. For each lot, 2 batches of 200 were held in 200L barrels at 48°56'N, 124°59 1 W under 3 photoperiod regimes: 1) natural daylength (control}; 2} 9.5h constant light for the first 60 days and then natural photoperiod; and 3) photoperiod cycle delayed to start at the winter solstice.
In August, 50 liquid nitrogen branded fish from each of the 18 batches were transferred to one of two 6x6x6m seapens. After 6 months, both photoperiod manipulations increased seawater survival, final mean weights, and uniformity of weight, for all lots. Seawater survival of 9.5h constant (64%} and delayed groups (69%} were significantly different (p<0.001) from controls (21%}. Mean roundweights (±lSD} of 9.5h constant (401±194g} and delayed (412±135g) groups differed significantly (p<0.0001} from controls (74±129g).
Hence, when egg-take times and incubation temperatures result in first feeding as late as March or April (previous studies have used February or earlier), photoperiod manipulation can be used to increase survival and growth rates of coho transferred to sea in their first summer. The total final biomasses achieved were 4.3 (control), 73.4 (9 .5h) and 83.6kg (delayed). Simple farm based photoperiod manipulation offers the salmon aquaculture industry the possibility of early transfer of young coho salmon to seawater grow out pens together with improved growth and survival in comparison to the normal life history and the resultant economic benefits of a condensed production cycle.