Wild salmon have been an integral part of Norwegian cultural heritage for as long as people have lived along its rivers and coasts. Over the past 40 years, salmon farming has grown from a small-scale coastal activity to a cornerstone of the Norwegian economy. This expansion has led to a significant increase in the biomass of farmed fish in coastal waters, altering disease dynamics between farmed and wild salmon. While the impact of parasitic sea lice is well-documented, there is limited knowledge about the role of other pathogens, such as viruses, bacteria, and microparasites. The PACE project was established to address this knowledge gap and investigate how infectious agents and climate change impact wild salmon populations along the Norwegian coast. With Northern Norway hosting some of the world’s largest remaining wild salmon stocks and experiencing a rapid increase in aquaculture activity, understanding these interactions is crucial for the future of both wild fish populations and the ecosystems they inhabit.
The PACE project analyzed gill samples from salmon and sea trout across Norway to determine which pathogens wild fish are exposed to and how these pathogens affect behavior. Results revealed a clear geographical gradient in pathogen diversity, with fish in the north harboring fewer compared to their southern counterparts. This is largely due to the lower levels of aquaculture activity and cooler water temperatures in the north, which have limited pathogen exposure in wild fish. However, increasing aquaculture production and rising ocean temperatures are expected to amplify existing pathogens in northern waters. While new pathogens are unlikely to be introduced, the increased pathogen load could disrupt the balance in these ecosystems, placing additional pressure on wild salmon populations that have not previously faced high infection rates.
Another critical aspect of the project was to examine how pathogens influence fish behavior and physiology. Using acoustic tracking devices and advanced genetic analyses, researchers found that the infection burden, measured as the number of pathogens per individual, had a subtle but measurable effect on sea trout activity levels. The study also showed that the behavior of wild salmon and sea trout was primarily influenced by river- and region-specific factors rather than pathogen burden. The summer of 2024, marked by a heatwave and a subsequent sea lice epidemic, demonstrated how climate change and increasing aquaculture production can combine to create challenging conditions for wild salmon. These findings highlight the importance of understanding the interactions between temperature, pathogens, and the physiology of wild salmon, particularly in the context of future climate scenarios.
The results of the PACE project provide valuable insights for both research and management. They contribute to a better understanding of how we can balance the need for increased food production with the conservation of Norway's unique wild salmon populations. Through collaboration with international researchers, the project has also developed new methods and tools, such as genomic analyses of gill tissue, which can be applied in future studies. This work establishes a strong foundation for understanding how climate change and human activities affect Norwegian coastal ecosystems and ensures that management decisions for aquaculture and wild fish are based on the best available science.
Resultatene fra PACE-prosjektet representerer et betydelig fremskritt i vår forståelse av samspillet mellom oppdrett, sykdommer og klimaendringer, og hvordan dette påvirker ville laksefisk langs Norges kyst. Prosjektet har avdekket hvordan patogener, påvirker villfisk, samt hvordan dette kan påvirkes av oppdrettsaktivitet og stigende havtemperaturer. Kartleggingen av sykdomsmangfoldet hos villaks og sjøørret fra sør til nord har gitt verdifull innsikt i sykdomsdynamikk og deres geografiske variasjoner. Denne kunnskapen legger grunnlaget for en bedre forvaltning av villfiskpopulasjoner, samtidig som den styrker beslutningsgrunnlaget for regulering av oppdrettsnæringen. Bruken av avanserte teknologier som akustisk telemetri og genomiske analyser har muliggjort studier av hvordan sykdommer påvirker fiskenes adferd, migrasjonsmønstre og fysiologi.
En av de mest viktigste funnene er at lakselus forblir det eneste marine patogenet i Norge som har dokumenterte populasjonsnivåeffekter på villaks. Dette er en avgjørende faktor å ta hensyn til i vurderingen av økt oppdrett i nord, hvor villaksbestander hittil har vært skjermet fra høy sykdomsbelastning. Resultatene viser at økt oppdrettsaktivitet, kombinert med stigende temperaturer, kan føre til øke smittepress fra oppdrett. Studien avdekket også en gradient i patogenmangfold fra sør til nord i Norge, noe som understreker behovet for økt overvåkning i Nord-Norge. .
PACE-prosjektet har også bidratt til å styrke samarbeidet mellom forskningsmiljøer i Norge og Canada, noe som har resultert i utviklingen av nye metoder og modeller. Gjennom integrering av økologiske og molekylære teknikker har forskerne økt forståelsen av hvordan patogener påvirker fiskehelse og adferd. Dette har allerede resultert i nye prosjekter, som pathDNA, som bruker miljø-DNA for å overvåke patogenutbredelse rundt oppdrettsanlegg. Resultatene har betydelige implikasjoner for norsk industri, spesielt innen oppdrettsnæringen, ved å legge til rette for bedre overvåkning av patgoenere, samtidig som de bidrar til å bevare ville fiskebestander. Den omfattende databasen som er opprettet gjennom prosjektet, utgjør en verdifull ressurs for fremtidig forskning og forvaltning
Little is known about the diversity and distribution of salmonid pathogens and their impacts on individual performance. In Norway, this knowledge is essential to understanding ecosystem dynamics given that terrestrial, marine, and freshwater environments are linked by migratory salmonids. A changing seascape due to anthropogenic activity and climate change means host-pathogen dynamics are likely to shift, necessitating an understanding of these processes for both fundamental and applied science. Presently, this knowledge is lacking in Norway. The PACE project will implement state of the art tools in fish biopsy and tracking to model the diversity and distribution of viruses, bacteria, and parasites of Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) along a latitudinal gradient in Norway and evaluate how these affect performance. Southern Norway is characterized by warmer temperatures and higher density of aquaculture and also more threatened stocks of salmon and sea trout. Northern regions are now exposed to relatively rapid warming and soon will encounter expansion of aquaculture activities. The interaction between climate and pathogens could threaten the viability of aquaculture as well as the native wild fish stocks in the north. In three work packages we will use molecular genomics to reveal pathogen biogeography and with biotelemetry and bioenergetics modeling we will investigate how pathogens impact fish performance in terms of physiology, behaviour, and life history. Results from the PACE project will be new and highly valuable knowledge to be used by aquaculture and industry regulators working to maximize sustainability of these operations. Tourism, fishing industries, and the environment will benefit from a more complete understanding of the salmonid host-pathogen ecosystem developed through PACE.
