Norway's scientist finds way to increase carp disease resistance 

Scientists in Norway have found that farmer can fight the Koi Herpes Virus (KHV) in carp due to the fact that the disease is highly heritable.

The common carp is the third most important farmed fish species in the world. It is produced in Europe and Asia, which both have KHV.

The project was conducted by Dr Jorgen Odegard, researcher in Nofima (Food, Fisheries and Aquaculture Research Norway) and their partners in the EU project, EUROCARP. The study was presented at Aquaculture Europe recently.

Researchers crossed individuals of four common carp strains of wild and cultured origin, and tested their survival after KHV infection. For each family, 20 individuals were tested. The 91 families that were tested showed very large variation in survival after infection.

The survival rates of the purebred strains and their crosses varied between 0 and 8 percent after testing. In spite of the low variation between strains and crosses, there was a large genetic variation within strains and crosses. Out of the 91 families tested, 60 were completely wiped out by the disease, but there were families showing up to 45 percent survival.

Odegard said that although there was a high overall mortality rate, there are good reasons for optimism.

The large variation between families shows that the genetics of common carp is crucial for the resistance against KHV, and research done shows that 80 percent of the variation in resistance to this disease is due to different genes of the individual.

This means that by applying a selective breeding programme, KHV resistance in common carp could be significantly improved in a few generations.

Currently, selective breeding programmes for carps are limited, unlike major aquaculture species such as tilapia, shrimp and salmon.