A study on the genetic relationship between salmon lice resistance and disease resistance in Atlantic salmon
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- Master's theses (IHA) 
The aim of this study is to find the genetic relations between resistance to salmon lice and resistance to other diseases. Three groups of Atlantic salmon from 279 full-sib families (offspring of 140 sires and 279 dams, year-class 2007) were challenged with causative agents of furunculosis and ISA as pre-smolts and IPN as post-smolts by means of cohabitation and recorded as survival. A forth group of Atlantic salmon from 154 full-sib families (offspring of 78 sires and 154 dams) of these families were reared in two replicated tanks and infected with two levels of lice per fish (74 and 36 copepodids per fish, respectively). Sessile lice were recorded as lice number per fish (LC) and lice density per fish (LD) were calculated as "LD=LC/Body weight2/3" . Harvest body weight was recorded on two subsamples of the same families as the lice infected group and additional 133 additional full-sib families (offspring of 62 sires and 133 dams). Estimated heritabilities of resistance to furunculosis (0.51), ISA (0.33), IPN (0.39), salmon lice (0.26) and harvest body weight (0.38) were all of moderate levels which indicates a great potential for improving resistance to diseases and growth rate by performing selective breeding. The genetic correlations between each two of the three survival traits were all positive and significantly different from zero (0.21 to 0.50) while genetic correlations between resistance to salmon lice and resistance to each of the three survival traits or harvest body weight were all weak and close to zero (−0.17 to 0.05). It is concluded that these studied traits can be simultaneously improved through selective breeding.