This year’s eyed eggs of rainbow trout from Aqua Gen are the first generation in which the parents have been selected based on high resistance to IPN.  In the last few years IPN in rainbow trout fry has been a problem, but selective breeding as a means of reducing the incidence of the disease is quite new in commercial breeding programs.

In 2006 an infection test was carried out with IPN on 200 families of newly start-fed fry. The mortality for the different families varied from 0 to 87 %. The degree of inheritance for IPN-resistance was calculated after the infection test to be 0.29 which means that 29 % of IPN-resistance is due to genetic factors.

Based on this result it is possible to make good progress in IPN-resistance through selective breeding. Families which had 4% mortality or less were used as brood fish at stripping this year.

Upgrading the breeding program

Since 2006 Aqua Gen has used more resources on the selective breeding program for rainbow trout. Several traits have been registered, and the three cohorts have been amalgamated into one population. The advantages of this are that selection can be amplified and that variation from year to year in genetic material is reduced.

Extension of the Season for Rainbow Trout

Customers now have a possibility to stock both early and late Rainbow Trout eggs over a period of five months from January to May. Early eggs (January) will provide a short production period so that these fish can be placed in the sea as early 0-year smolts whereas late eggs (May) will produce 1-year smolts.

As a result production capacity can be better exploited by placing a larger percentage of the fish in the sea as 1-year smolts in the spring. This leads in its turn to a more even harvesting of fish for slaughter.