Sex Determination in Tasmanian Atlantic Salmon

Although male heterogamety controls Atlantic salmon sex, hormone treatment can induce sex reversal. In Australia where Atlantic salmon males are unmarketable, sex reversed females (neo-males) are crossed with females to produce all female stock. However, neo-males are indistinguishable from males making early male culling difficult. Therefore, a sex-specific genetic marker was needed to make this distinction. With no such marker available offspring sex was predicted via familial microsatellite analysis. Markers from Chromosome 2 (Ssa02), where the sex locus (SEX) previously mapped, predicted test family offspring sex inaccurately. A 64 SNP genome-wide scan suggested Chromosome 6 (Ssa06) housed SEX instead. Analysis of 38 male lineages revealed three sex loci on Ssa02, Ssa06 and Ssa03 with 34, 22 and 2 representative families respectively. An exon PCR test for the rainbow trout master sex-determining gene (sdY) was consistent with a single sex-determining gene that jumps around the genome in Atlantic salmon.