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Information Letter Nr. 1 / 2012

Field results of QTL-innOva IPN - from egg to harvestThe first generation of QTL-IPN fish from Aqua Gen has now been follo-wed throughout the entire producti-on cycle. The results show that the prevalence and extent of IPN in both fresh water and sea water were either eliminated or significantly reduced in comparison to previous genera-tions and reference groups that did not possess the QTL-IPN. This positive trend is confirmed by official statis-tics on the number of registered IPN outbreaks in the Norwegian fish far-ming industry. It is expected that the increased frequency of IPN resistant QTL fish, combined with reduced in-fection pressure in the environment will further improve the disease situa-tion and reduce losses in the coming years, resulting in improvements for both animal welfare and profitability in the fish farming sector.

Major increase in the use of QTL eggsAqua Gen introduced the first QTL-IPN eggs in autumn 2009 to the Norwegian market. In the 2009/10 season a total of 45 million QTL eggs were delivered to customers that historically had experi-enced major challenges with IPN in both fresh water and sea water. This represen-ted about 12 % of the entire Norwegian egg intake in that season. Based on the positive field results from this year-class, Aqua Gen has seen a significant increase in demand for QTL eggs in the European market.

Nearly 350 million QTL eggs from Aqua Gen have been delivered to Norwegian hatcheries in the last 3 years. With 170 million QTL eggs in the season 2011/12,

the percentage of QTL eggs of the total year-class has risen to nearly 50 %. This growing proportion of IPN resistant fish in the salmon industry has contributed to a positive trend of reducing registe-red IPN outbreaks and increasing survi-val throughout the production cycle.

Reduction in IPN outbreaksAccording to the Norwegian Veterinary Institute’s official statistics, the number of recorded outbreaks of IPN in the sal-mon industry has reduced from 221 out-breaks in 2009 to 149 outbreaks in 2011. This represents a reduction of 33 % on a national scale over the past 2 years.

The first groups of QTL fish from Aqua Gen have now been through the entire

production cycle from egg to harvest. In this information letter, we will sum-marize the results from those groups we have followed through fresh water (egg intake 2009/10) and sea water (smolt transferred to sea autumn 2010 and spring 2011) and which have been through the most critical phase for IPN.

Results in fresh waterIn the period from November 2009 to May 2010, we followed 15 fresh water sites that stocked a total of 29.1 million QTL eggs. These sites that participated in the field investigation had historically experienced significant losses due to IPN. Of the 15 sites which stocked QTL eggs this season, none experienced cli-nical outbreaks of IPN in the fresh water

phase. One site was diagnosed with IPN virus, but with negligible mortality (0.2 %).

We also established a reference group, consisting of 14 sites that received a total of 23.1 million standard eggs. These were sites that did not have the same very serious IPN histories as those in the experimental groups, and the-

refore were not directly comparable. Among the sites within this reference group there were diagnoses of IPN on 6 out of 14 sites, with mortality rates at the group level which ranged from 0.5 to 7.0 %. Sites with standard eggs had the same level of IPN as the previous season. The results are summarized in table 1.

Table 2. Results from the field investigation of S0, autumn 2010. The table shows the number of smolt transferred, number of sea sites represented, average mortality the first 90 days post transfer and diagnosed IPN +/- for QTL-smolt and non QTL-smolt in 2010.

Table 1. Results from field investigation of QTL-stock in fresh water sites. The table shows the number of eggs placed in the sites, number of sites represented and average mortality during IPN diagnoses/outbreak for QTL-stock and non QTL-stock in the period November 2009-May 2010. For comparision, the IPN history in 2008/2009, when there were non QTL-stock only in the same sites are also shown.

Table 3. Results from the field investigation of S1, spring 2011. The table shows the number of smolt transferred, number of sea sites represented, average mortality the first 90 days post transfer and diagnosed IPN +/- for QTL-smolt and non QTL-smolt in 2011.

S0 group Number of fish Number of sea water sites

Average mortality 90 days post transfer (%)

Number of IPN diagnoses

QTL-smolt 2010 5,597,905 11 1.1 0

Non QTL-smolt 2010 2,321,243 7 6.4 1

Egg-fry group Number of eggs

Number of fresh water

sites

Average mortality during IPN diagnoses/

outbreak (%)

Number of IPN diagnoses

2009/2010

Number of IPN diagnoses of non

QTL-stock 2008/2009QTL-stock 2009/2010 29,078,526 15 0.2 1 7

Non QTL-stock 2009/2010 23,069,860 14 0.5-7.0 6 5

S1 group Number of fish Number of sea water sites

Average mortality 90 days post transfer (%)

Number of IPN diagnoses

QTL-smolt 2011 11,409,785 14 4.6 3

Non QTL-smolt 2011 11,255,630 12 12.7 7

Results in sea waterFor the sea water phase, we followed two smolt groups, autumn 2010 (5.6 million fish in 11 sites) and spring 2011 (11.4 million fish in 14 sites). As with the fresh water survey, we established refe-rence groups on sites that used standard smolt only (table 2 and 3).

S0, autumn 2010For fish of QTL origin transferred as smolts in autumn 2010 there were no

diagnoses of IPN. Average mortality recorded to 90 days after transfer was 1.1 %. For the reference group IPN was found on one site and the average mor-tality recorded to 90 days after transfer at the 7 sites was 6.4 %. The results are summarized in table 2.

S1, spring 2011For QTL fish transferred in spring 2011, IPN was diagnosed at 3 out of 14 sites. Average mortality recorded to 90 days

after transfer at 14 sites was 4.6 %. In the IPN positive sites mortality varied from 5 to 9 %. The clinical picture of the 3 cases was complex, with both smolt quality and bacterial infection contributing to mortality. In the 12 reference sites, IPN outbreaks were recorded at 7 sites, and the average mortality recorded to 90 days post sea transfer was 12.7 %. In the IPN positive sites, mortality varied from 3.2 to 38.0 %. The results are summari-zed in table 3.

Aqua Gen sea site, Hafsmo, May 2012: Aqua Gen employees are doing the final selection and sampling from broodstock for QTL-analysis.

Testing of QTL status at IPN occurrenceIn collaboration with the fish health ser-vice and personnel at the QTL farms that experienced IPN outbreaks, we imple-mented a test program for analyzing the QTL status of fish that died /survived the outbreaks. The fish were tested both for the presence of the IPN virus and to see if they had the marker for IPN resistance.

The results from the testing showed that the majority of fish that died of IPN did not have the correct QTL status, mea-ning that they lacked the marker for IPN resistance. The frequency of fish with the incorrect QTL status in these groups was

The samples from the broodstock are ana-lyzed for QTL-staus in the lab.

in the range of 2 to 8 %. This is proba-bly a result of errors in the test methodo-logy used to genotype the broodstock from Aqua Gen. Although this type of analysis can never be 100 % accurate, we have now improved the analytical method and quality-assurance work on further genotyping and as a result sub-sequent selection of broodstock is now more precise.

The first harvest resultsThe first S0 group of QTL fish transferred to sea 2010 were harvested in October 2011, 13 months after sea transfer. This was part of a group, farmed in the

county of Nordland in Northern Norway of approximately 600,000 fish. The result from stocking shows that over 95.8 % of the fish transferred to sea reached a mar-ket size of at least 4.5 kilograms, with a superior rate of 96.8 % and a biological and economic feed conversion of 1.03 and 1.04 respectively. Although this pro-bably is not representative of all groups in the field experiment, such results and feedback are inspiring, and strengthens us in the belief that we as geneticists and egg supplier are a significant contri-butor to the success of future develop-ment of the aquaculture industry.

Aqua Gen AS • PO Box 1240 • Sluppen • N-7462 Trondheim Phone. +47 72 45 05 00 • Fax. +47 73 54 62 91 • firmapost@aquagen.no • www.aquagen.no

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