Differences in growth, pond survival and CyHV-3 disease survival between genetically CyHV-3 resistant and commercial strains of common carp (Cyprinus carpio)

Not only is aquaculture required to increase production to meet the growing demand for food, it also holds a great potential to do so. Improvements in growth traits are key to make production more efficient. However, since outbreaks of infectious diseases place significant impediments to further growth of this sector, it is also key to incorporate disease resistance into food fish stocks. Common carp is a key aquaculture species suffering from a global disease caused by cyprinid herpes virus type 3. We have been successfully breeding for disease resistant strains by introgression of resistance from a feral strain, followed by backcross generations to food strains and family selection for resistance. Here, we compared between our disease resistant strain and a commercial food strain for growth and pond survival by a communal field trial and for resistance by a controlled disease challenge. We found that the commercial strain had an initial advantage, which accumulated to a relative weight advantage of 25 % after 468 days. However, the advantage in specific growth rate the commercial strain had at the beginning diminished and reversed to a disadvantage at the middle of trial. On the other hand, the resistant strain had a relative advantage of 43 % in disease resistance. Thus, improving disease resistance by introgression and selection was a successful strategy, which did not compromise significantly growth rate, even without any selection for growth so far. Here, growth rate and disease resistance were not correlated and thus, growth can be improved alongside disease resistance in future selection. Given the importance of disease resistance in aquaculture, breeding by introgression and selection that worked well for carp, which had been already bred for several aquaculture traits, can certainly be considered in other species, especially those without a progressive breeding program.