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Salmon lice dominated 2016 fish health challenges in Norway

2016 Fiskehelserapporten pictureUpdated figures indicate that more salmon die because of changing treatments against salmon lice. Increased resistance against pharmaceuticals lead more and more farmers to choose none pharmaceutical treatments. This is much harder on the fish. It is estimated that 20 percent, or one of every five salmon released into the ocean, is lost.

The Norwegian Veterinary Institute (NVI) released their 2016 Fish Health Report today. This is a comprehensive status of Norwegian fish health, including statistics, surveillance results and risk analysis for all the important fish diseases.

“Not all, but very many farmed fish are doing very well in Norway today. The value of what is produced is significant, but the fish farming industry still has a huge potential for improvement in fish health and welfare,” according to Brit Hjeltnes, Director for Fish Health at the Norwegian Veterinary Institute.

Indication of increased mortality when changing de-lousing methods

The 2016 Fish Health Report shows that there were about the same number of lice in 2016 as in 2015. Registration shows an increase in the southern areas of Norway and a reduction in the areas in mid-Norway.

The total number of lice treatments saw a 10 percent decrease in 2016 compared to 2015. The largest change was found within the treatment methods. The number of pharmaceutical treatments went down about 41 percent, while the none pharmaceutical treatments increased formidable 535 percent (from 185 in 2015 to 1174 in 2016).

In a survey published as a part of the report, 9 of 10 fish health workers (93 percent) report that they experience increased mortality when none pharmaceutical methods are used. Sixty-five percent report significant mortality when using pharmaceutical methods.

“Lice issues rightfully received a lot of attention in 2016. In the past, lice have usually been viewed as a threat against the wild population. In 2016 lice became a serious problem for farmed salmon as well,” Brit Hjeltnes said. She also clarified that it is important not to forget the other diseases, and the total toll they have on the fish, in order to understand that the none pharmaceutical de-lousing methods seems to be tougher for the fish.

Pancreas Disease (PD) in mid-Norway

PD is still the most serious viral disease among salmon in seawater farming. The number of outbreaks and suspected outbreaks were at about the same level as 2015. In 2016, a total of 138 sea farms had proven cases of pancreas disease.

Infectious Salmon Anemia (ISA)

In 2016, 12 localities in Nordland (8), Sør-Trøndelag (3) and Finmark (1). Two cases in Frøya in June 2016 may be related to ISA cases in Møre og Romsdal in 2014 and 2015. The third case in Frøya in 2016 was most likely a primary outbreak. The same goes for the ISA outbreak in Finmark in December 2016.

Cardiomyopathy Syndrome (CMS)

Cardiomyopathy Syndrome is a very serious heart disease affecting farmed salmon. The NVI found CMS in 90 localities in 2016 compared to 105 in 2015.

Gill Disease

There seems to be some variation in gill disease outbreaks from year to year, but the disease continues to be an ongoing problem for salmon in Norwegian farms. Rainbow trout seems to have less problems with gill health than salmon.

Cleaner fish

Almost 26.4 million cleaner fish were released in 2015, or about two million more than in 2014. More attention to disease issues for cleaner fish was seen in 2016, such as atypical furunculosis, classical furunculosis and Amoebic gill disease (AGD). At the end of 2016 it became more known that the cleaner fish itself is affected by lice (Caligus elongates).

Low antibiotics use

The use of antibiotics in 2016 was at its lowest level since the middle of the 1970s. The total amount of antibiotic pharmaceuticals used in farmed fish in 2016 was 212 kilos (active substance). Very little antibiotics are used in salmon in sea farms. Data from the Norwegian veterinary pharmaceutical register (Vetreg) shows that most prescriptions were written for cleaner fish, but cleaner fish contributes relatively little to the overall antibiotics use.

The 2016 Fish Health Report describe the health and welfare problems related to implementation of new technologies, such as lice treatment and recirculating farming systems (RAS).

For a copy of the report (Norwegian only), click here.

For further information, please contact:

Brit Hjeltnes, Director Fish Health, Norwegian Veterinary Institute, brit.hjeltnes@vetinst.no