More to keep the boys busy answering and scratching their heads.
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Farmed Salmon disease jump to Wild Salmon ... overview of a new NINA (Norways environmental department ) report .
Åse Helen Garseth is a researcher at the Veterinary Institute and a member of the RCL.
In Norway, we have a stock of approximately 350 million (700,000 tonnes) of farmed Atlantic salmon distributed at approx. 600 active locations along the coast. During the sea phase, the salmon is bred mainly in open cages. This farming situation, where a large number of individuals are kept in a relatively small volume, involves on the one hand infection exchange between individuals within the cage, and on the other hand that the infection can spread to the surrounding environment and wild fish. In addition, a large number of farmed fish escapes every year and a proportion of these find their way up the rivers. The described situation is the reason why infectious diseases in fish farming are considered a threat to wild salmonids.
Infectious status in the aquaculture industry
In the project Lack of salmon fish in the sea, conducted by the Norwegian Food Safety Authority and FHF in 2013, it was shown that 6-7% of farmed fish died as a result of infectious diseases during the period between sea and slaughter. Infections are thus one of the major biological and economic challenges in the aquaculture industry. The Veterinary Institute has for a number of years described the number of cases of the various fish diseases in its annual Fisheries Report.
Although many of the important bacterial diseases in the industry are controlled using vaccines, it remains to get knowledge and control of several microorganisms and parasites. In 2016, the Veterinary Institute diagnosed 360 cases of viral disease in the sea (pancreatic disease - PD 138, infectious pancreatic necrosis - IPN 19, infectious salmon anemia - ILA 12, heart and skeletal muscle inflammation - HSMB 101 and cardiomyopathy syndrome - CMS 90) (Fish Health Report). The number of cases of non-notifiable diseases IPN, CMS and HSMB is probably higher, since the diagnoses can also be made by private laboratories and fish health services.
It has taken decades to come where we are today in terms of knowledge about salmon lice and interaction wild-farming. We must acknowledge that research on the effects of other infectious diseases in fish farming today is hardly the starting point.
Outbreaks of disease at a site with nearly 600,000 individuals provide a significant development and excretion of environmental pollution. Several of the important contaminants in fish are robust in the marine environment and spread horizontally from cages to cages, from plant to plant, and to transport of fish. Therefore, wild salmon that resides in the same marine environment is also exposed to a contagion pressure from the aquaculture industry. In addition, as described, infected escaped fish constitute a challenge. Runaway farmed fish go up in rivers also outside areas of farming, and surveys have so far shown that there is higher odds for detecting infection of escaped fish than in wild fish. The Veterinary Institute has conducted studies in which the relationship between virus from farmed fish and wild salmon fish has been analyzed. These show that viruses are exchanged between wild fish and farmed fish.
Infection status of wild salmonids
Knowledge of the health of wild fish is generated through passive and active health monitoring, and through research. The Veterinary Institute takes care of the public's responsibility to resolve disease suspicion and inexplicable mortality in wild fish. Such clarifications constitute the passive part of the health surveillance and contribute both to increasing knowledge about the health and disease of wild fish, and to maintain healthy populations. Disease detection in wild fish is also an important contribution to the preparedness and monitoring of the interaction between infections in farmed and wild fish populations.
The active monitoring programs are carried out on behalf of the Norwegian Food Safety Authority. Traditionally, the results from these programs have provided an important evidence of the freedom or presence of specific infections. The prevalence of Gyrodactylus salaris has been monitored in this way over several years.
Monitored since 2012
Since 2012, the Institute of Marine Research and the Veterinary Institute has carried out health surveillance of wild anadrom salmon fish on behalf of the Norwegian Food Safety Authority. The monitoring program has mainly focused on viruses that are common and cause disease challenges in the aquaculture industry, but have only partially followed the same template as used for other surveillance programs. The reason for this is that repeated monitoring of agents, which one can not easily detect in wild fish, has no utility as long as you do not know why you are not detecting them.
In the period 2012-2014, the incidence of viruses giving ILA (ILAV), PD (SAV), IPN (IPNV), HSMB (PRV) and CMS (PMCV) was investigated. The Veterinary Institute had largely already carried out mapping of these viruses and thus had a basis for assessing the usefulness of the monitoring. The main findings of the Veterinary Institute's part of health monitoring are summarized in the table below.
Virus IPNV SAV ISAV PMCV PRV
Veterinary Institute's Health Monitoring
Number tested