Smoltification and growth experiment
In farmed Atlantic salmon, high survival, growth and robustness in the seawater phase is critical for good animal welfare and a good economic result. In the current breeding programs, genetic improvement of these traits is sought through selection for increased growth until harvest size and increased survival in specific disease challenge tests. Several studies suggested that mortality and sub-optimal growth in the early phase of sea-transfer could be traced to sub-optimal smolts. However, comparison of individual growth for fish of different smoltification status has never been done. Thus, in the main experiment, the aim is to study the growth and survival of fish with different smoltification status (assessed by different blood serum ions (Cl-, Na+, K+, Mg2+) and Na+, K+ -ATPase activity in the gills).
A pilot test will be conducted before the main experiment starting with 170 fish of average body weight 70g smoltified fish. The main purpose of the pilot is to train technical staff at Nofima, Sunndalsøra in taking non-lethal gill biopsy and blood samples (in combination or alone) on post-smolt A. salmon, to obtain a relative rough estimate of the effect of these procedures on the growth, swimming and feeding behaviour of the fish over a six weeks period in seawater, and to develop a more refined protocol for non-lethal sampling of gill biopsy and blood which can be used to fine tuning the design and sampling procedures of the main experiment, as well as in similar future experiments.
The results from the pilot test will be used to fine tune the design and the protocol of the main experiment which will be conducted during a 12 week smoltification period (6 weeks on 12L:12D and 6 weeks on 24L:0D) and will start with 1000 fish that will be PIT-tagged at an average body weight of 70g five weeks before the 12 week smoltification period. During the 6 weeks 24L:0D period, a small group of fish will be sampled every week for either gill biopsy and blood, or both gill and blood, after which they will be transferred to saltwater. After the 12 weeks smoltification period, the fish will continue for grow-out in the saltwater for another 12 weeks, and their body weight and length will be recorded at Week 6 and Week 12 of this grow-out period.
A pilot test will be conducted before the main experiment starting with 170 fish of average body weight 70g smoltified fish. The main purpose of the pilot is to train technical staff at Nofima, Sunndalsøra in taking non-lethal gill biopsy and blood samples (in combination or alone) on post-smolt A. salmon, to obtain a relative rough estimate of the effect of these procedures on the growth, swimming and feeding behaviour of the fish over a six weeks period in seawater, and to develop a more refined protocol for non-lethal sampling of gill biopsy and blood which can be used to fine tuning the design and sampling procedures of the main experiment, as well as in similar future experiments.
The results from the pilot test will be used to fine tune the design and the protocol of the main experiment which will be conducted during a 12 week smoltification period (6 weeks on 12L:12D and 6 weeks on 24L:0D) and will start with 1000 fish that will be PIT-tagged at an average body weight of 70g five weeks before the 12 week smoltification period. During the 6 weeks 24L:0D period, a small group of fish will be sampled every week for either gill biopsy and blood, or both gill and blood, after which they will be transferred to saltwater. After the 12 weeks smoltification period, the fish will continue for grow-out in the saltwater for another 12 weeks, and their body weight and length will be recorded at Week 6 and Week 12 of this grow-out period.