The transgenic line was initiated in 1989 with injection of this
construct into fertilized salmon eggs from the St John's wild stock.
Mendelian inheritance of the GH transgene and its rapid growth phenotype
was established at the F2 generation and has been observed
through the sixth generation (Fletcher et al., 2004). In general, the
transgenics grow most rapidly through their first year of life (Du et al.,
1992), and at about 1 kg, their growth rates slow to those of nontransgenic
salmon. Transgenic fish used in this study were crosses of
the transgenic line with the St. John's aquaculture stock, i.e., they were
hemizygotes for the transgene, representing the animals that would
be subjected to triploidy induction and produced in the event of approval
of the transgenic salmon for commercial production. Triploids induced
by application of hydrostatic pressure to newly fertilized eggs
(Benfey and Sutterlin, 1984a) that were derived from the St. John's
stock. AquaBounty Technologies will produce triploid GH-transgenic
Atlantic salmon only in the advent of the pilot-scale production study
for which they seek regulatory approval; hence, triploid transgenics
were not available for our evaluation.