fish health

Harvest weight and pancreas disease in Norway

High sea lice and PD levels could negatively impact the salmon’s appetite and growth and increase cost/kg and result in less volumes.

Pancreas Disease (PD)

Feed sales and harvest weight is linked to sea lice and PD

Vetinst.no publishes data on PD once a month. High levels of PD and sea lice will translate to low feeding and growth.

 

PD can impact growth and weight and the harvest weight can have an impact on the achieved salmon prices. The weekly update from Jon Arne Grøttum and SjømatNorge shows harvest weights in Norway.

The cost per kg declines with increasing harvest weight, which is positive. Opposite, if salmon is harvested at a lower weight than optimal (caused by for example diseases, such as PD – see more on PD below),  costs per kg will be higher.

With higher harvest weights, the fish farmer will, at any given volume level, require fewer fish individuals than planned. The excess fish individuals will be saved for harvest later in the season, hence increasing volumes but also adding to price pressure.

What is PD?

PD is an infectious disease of farmed Atlantic salmon and rainbow trout caused by the Salmonid Alphavirus (SAV). In Norway, the number of PD outbreaks has increased with harvest volumes.

 

SAV is found naturally in wild salmon and trout in several geographical regions as well as other species of wild fish. As the chart shows, more than a decade ago, PD was mainly found in the South of Norway, but has slowly spread to mid-Norway and further to the North.

Still, the lion’s share of the PD incidents are observed in Mid Norway and Central Norway.

 

PD can occur in the first or second year in seawater and is most commonly diagnosed in the period May-September when water temperatures are higher. Besides damage to the pancreas, severe cardiac and skeletal myopathies can be features of this disease.

In addition, infected fish lose their appetite and become lethargic. Outbreaks can last from 3-8 months. Variable mortality rates are attributed to PD.

How do you prevent PD?

Farmers should use sound farming practices, proven policy principles and keep fish in conditions that satisfy their biological needs for food, clean water, space and habitat.

Focus must be on disease prevention and supervision. Water quality, temperature, salinity and oxygen must be continually checked, also during transport. All fish in regions with high risk of PD are vaccinated.

Farmers should check for and remove fish mortality on a frequent basis and all mortalities should be handled in a way that minimises the risk of disease spread. In addition, farmers should cooperate with other producers on disease control, coordination of mitigation measures and fallowing.

The incidence of the disease has been reduced in recent years.

What happens to fish that is infected?

Although fish are vaccinated, there is a possibility they can become infected. Farmers must check for and remove fish that are infected, but it is not possible to treat the infection. Diseased fish are discarded at harvest.

Most fish harvested from a farm suffering from PD are unaffected and/or express immunity. In these fish, there is no damage to the fish tissues and quality is not compromised.

Is it dangerous to eat salmon that is infected with PD?

No, SAV does not transfer or infect humans and is not a health risk.

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