Abstract
Vertebral deformities in salmonid interspecific hybrids, some of which were triploidised, were assessed across three separate year classes during the freshwater life stage. Initially, eggs from a farmed Atlantic salmon Salmo salar were crossed with the sperm from a S. salar, arctic char Salvelinus alpinus or brown trout Salmo trutta. For S. salar × S. trutta, half the eggs were triploidised. In a second- and third-year class, the eggs from a farmed S. salar were crossed with the sperm from either a S. salar or a S. trutta, and half of each group was triploidised. In the two initial-year classes, all hybrids were larger than the S. salar controls, and triploid S. salar × S. trutta were larger than diploid counterparts. In the third-year class, the S. salar × S. trutta were smaller than the S. salar, in contrast to the initial 2 year classes, although the triploid hybrids were still larger than the diploids. In the third-year class, a high degree of spontaneous triploidy was also observed in the putative diploid groups (between 16 and 39%). Vertebral deformities were consistently higher in pressure-shocked triploids than diploids, irrespective of hybridisation, but there was no consistent effect of hybridisation among experiments. Although this study was not able to explain the contrasting results for vertebral deformities between year classes, triploid S. salar × S. trutta can demonstrate impressive freshwater growth that could be of interest for future farming programmes.
Highlights
Interspecific hybrids can be used in aquaculture to increase growth rates, transfer/combine desirable traits between species or induce sterility (Bartley et al, 2001)
Year-class effects were observed on the prevalence and severity of vertebral deformities in interspecific salmonid hybrids
This study rejected the hypothesis that triploidy would lead to an increase in vertebral deformities, as ploidy effects were not significant within S. salar × S. trutta in one of the 3 year classes
Summary
Interspecific hybrids can be used in aquaculture to increase growth rates, transfer/combine desirable traits between species or induce sterility (Bartley et al, 2001). Studies in cultured fish have found a number of salmonid hybrids to be viable, in terms of hatching and survival, but their traits are not commercially advantageous (Blanc & Chevassus, 1979; Gray et al, 1993; Scheerer & Thorgaard, 1983). These studies on hybrid performance were mainly carried out in the 1980s and 1990s.
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