Nr. 2 / 2008

During the 2007-2008 season Aqua Gen carried out a programme of exhaustive quality controls at the time of delivery of salmon eggs in Norway.   This investigation covered the period from egg delivery to 4 weeks after the beginning of feeding.  Generally the results showed a low incidence of non-viable eggs and a high survival rate throughout the whole period. Feedback concerning growth rates after the start of feeding has also been very positive.

Egg reception control

In order to ensure a good start for a new generation of salmon, representatives from Aqua Gen have been present on our customer's sites whilst shipments have been un-packed and eggs laid out in their hatcheries. A total of 67 controls on delivery were carried out on a total volume of 115 million eggs. Altogether 46 sites were visited during the period from the middle of November 2007 to the middle of March 2008.

Egg quality

During the quality controls the amount of non-viable eggs was recorded. Non-viable includes unfertilized eggs, pin-eyed eggs, white eggs (dead), and other (twins, triplets, and similar conditions). An average of 1.15 % non-viable eggs was found. The distribution among the four different categories of non-viable eggs was as follows:

Unfertilized eggs	0.23 %
Pin-eyed eggs	0.76 %
White eggs	0.03 %
Other	0.13 %
Total non-viable eggs	1.15 %

Amounts of non-viable eggs are shown in figure 1. The percentage of non-viable eggs at stocking will give an indication of expected hatching success. If, for example, we find 1.5 % non-viable eggs will the potential hatching percentage be 98.5 % or better. Feedback from the market has shown that this supposition appears to be true.

Presence of fungus

At the delivery control at the client the eggs have also been investigated for possible fungal infection before stocking. 9 cases were found where some eggs had clumped together and this was registered as a possible case of fungal infection. When reviewed it was seen that 7 of these observations were related to coagulated egg-sac material from eggs which had broken up. None of the clients this season have given feedback about problems with fungus during the hatching or fry phases.

Quantity control

In addition to quality samples the number of eggs delivered has also been controlled on site. No cases were found where too few eggs were delivered. At three clients the number delivered was found to be a little higher than the supplied overage of 5 %. The reason for this excess was a calibration error in the measurement of the eggs, which was quickly corrected.

Hatching results

Hatching success averaged 98.2 %. This number is based on the results of 36 deliveries and comprises a collective egg volume of about 61 million eggs (figure 2). The average hatching time was four days and the eggs were hatched at 491 day-degrees. This is a little lower than last year (the 2006/2007 season), which was around 500 day-degrees. The difference of 9 day-degrees corresponds to about one 24-hour day.

Some customers reported batches that had hatched earlier than they have usually been accustomed. The lowest day-degree sum at hatching this season was 472, and the highest was 515 day-degrees. Re-calculated to 24 -hour days with an incubation temperature of 8 degrees this makes a difference of 5.5 24-hour days. No correlation has been seen between low/high day-degree sum and subsequent survival.

Feedback from the fry phases

In the period from hatching to 4 weeks after start feeding we have received positive feedback. Start feeding has been successful, growth has been good, and only two cases of IPN among fry have been reported in this phase.

Comparison of egg producers

During this season eggs from Aqua Gen were produced at 5 brood fish plants: Aqua Gen department Hemne, Aqua Gen department Tingvoll, Marine Harvest department S-T, Marine Harvest department Tveitevåg and Aakvik Settefisk. In a comparison of hatching percent and quality it has not been possible to show a difference among the 5 producers.

 

PDF of the Information Letter is found here