Fishers and coastal communities along the Norwegian coast have claimed that salmon farms prevent Atlantic cod from using their traditional spawning grounds, and that this causes diminishing coastal cod populations. Given the declining coastal cod populations, many have also expressed concerns that fish farming might contribute to this decline. In this project, our goal was to gather comprehensive knowledge to clarify whether salmon farming negatively impacts wild cod stocks through a before-and-after study.
We began in winter 2019 by investigating Frakkfjord, located on the border between Troms and Finnmark County, prior to a planned salmon farming establishment in 2021. Additionally, we examined two reference fjords: one neighboring fjord with salmon farming (Langfjord) and one fjord without farming (Olderfjord).
Despite challenges posed by COVID-19, we tagged approximately 750 cod with acoustic transmitters. This unique dataset covers both coastal cod and Northeast Arctic cod (skrei), males and females across a wide size range, and spans multiple years (2019–2023). Their behavior was recorded through a network of acoustic receivers over a continuous five-year period, providing extremely detailed data on the behavior of free-swimming cod (WP 1).
We also captured, sampled (including genetic analyses to distinguish skrei from coastal cod), tagged, and released over 5,000 juvenile cod, yielding valuable data on density, growth, and migration of young coastal cod and northeast Arctic cod (WP 2). Fatty acid analyses revealed physiological effects linked to salmon farm feed spillage (WP 3). Additionally, we collected samples to study how cod utilize benthic resources (diet) and how these resources are influenced by fish farming (WP 4).
A literature review summarized known effects of salmon farming on cod (WP 5), and we engaged extensively with national, regional, and local stakeholders regarding spatial planning and coexistence between fisheries, aquaculture, and vulnerable ecosystems (WP 6).
The planned salmon farm in Frakkfjord was not established as expected in fall 2021. In agreement with project partners and the Research Council, we prioritized the comparative study (comparing fjords with and without aquaculture). Consequently, the aquaculture-intensive neighboring Langfjord was equipped with acoustic receivers from the autumn of 2022, and a large number of cod were captured, tagged, and released there as well. This provided an exceptional dataset to compare aspects of cod activities in the aquaculture-free Frakkfjord versus in the aquaculture-intensive Langfjord.
The SalCod project has allowed us to answer numerous unresolved questions about how salmon farming may affect both coastal cod and skrei in northern Norway. For example, in the article "Torsk mot strømmen", we described that migration patterns of coastal cod and skrei not always as distinct as previously thought. As expected, skrei tended to leave the fjord more often than coastal cod after spawning, but more skrei than anticipated remained in the fjord, while some coastal cod left (WP 1). Notably, some skrei grow up within the fjords!
We also gained insights into habitat preferences of coastal cod. Juvenile cod strongly prefer bottom structures with gravel and rocks, while larger coastal cod and skrei occupy deeper areas and move over broader ranges (WP 1 and WP 2). Some individuals specialize in foraging near fish farms, as evidenced by fatty acid composition in their livers. The fatty acid signal from fish farms was less pronounced in muscle tissue analyses (WP 3).
A combined study of benthic ecology and diet (analyzed using fatty acids and new eDNA methods) revealed that cod feed on a mix of natural benthic invertebrates and fish. However, 70% of cod caught near fish farms had diets influenced by salmon feed and benthic species tolerant of farm emissions (WP 4).
Our literature review confirmed that salmon farming can significantly affect cod behavior and physiology, potentially increasing mortality (WP 5). The project has generated new hypotheses and updated risk assessments for the upcoming edition of «Miljøvirkninger av Norsk Fiskeoppdrett» (February 2025), which will include a dedicated chapter on the impacts of aquaculture on wild marine fish.
The findings from the SalCod project highlight strong interactions between bottom structures, marine resources, aquaculture, and vulnerable ecosystems, demonstrating the coastal zone’s sensitivity to human activities.
Follow-up research from SalCod is already underway and will continue within the Institute of Marine Research’s new initiatives, CoastWatch and KystNord (2025–2028), as well as in proposals for “Store Satsninger 2026–2029”. If successful, these efforts could improve spatial planning and monitoring along the entire Norwegian coast. In the long term, this may be the most significant outcome of NFR's call for projects and the SalCod platform.
Prosjektet hadde som mål å skaffe til veie helhetlig kunnskap om, og eventuelt hvordan, lakseoppdrett påvirker torskepopulasjoner i nord. Dette ble forsøkt gjennomført i en før-etter-control-impact (BACI) studie av tre gytefjorder i Nord-Troms og Vest-Finnmark. Etableringen av det planlagte oppdrettsanlegget kom imidlertid ikke på plass som forutsatt i 2021. Prosjektet vektla derfor den komparative delen (sammenligne en fjord med og en fjord uten oppdrett). Prosjektet har framskaffet ny kunnskap om adferd og livshistorie til kysttorsk og skrei der disse lever sammen i våre nordlige fjordsystemer. Bruken av nyutviklede metoder for 3D posisjonering fra telemetridata, og koblingen til spesifikke habitat som torsken faktisk bruker, inkludert rundt oppdrettsanlegg, er unikt i en vitenskapelig sammenheng, men også spesielt relevant kunnskap for den arealbaserte forvaltningen langs kysten. Gjennom SalCod-plattformen har kunnskapen om telemetri, reproduksjon, fangst og genetikk til sentrale torskeforskere ved Havforskningsinstituttet (HI) blitt videreutviklet og satt inn i en akvakultursammenheng – i tett samarbeid med lakseforskere. HI kan derfor levere ny kunnskapsstatus og risikovurdering over effekter av lakseoppdrett på vill marin fisk, men også stille nye forskningshypoteser og redusere usikkerheten i viktig kunnskap. Dette vil på kort sikt kunne få effekter på forvaltningspraksis og politikk både nasjonalt, regionalt og lokalt. Kompetanseoppbygningen vil også kunne ha overføringsverdi til den raskt voksende torskeoppdrettsnæringen.
Den største betydningen av SalCod, på lengre sikt, er likevel at prosjektet har fungert som en brekkstang for økt forskning i kystsonen. Vi har for dårlig kunnskapsgrunnlag til å forvalte kystsonen. Dette gjelder både statlig sektorforvaltning, fylkeskommunal samordning og kommunal arealplanlegging. Konsekvensene kan bli at en ikke får tatt ut potensialet for verdiskapning, samt økt risiko for manglende bærekraft og feil lokalisering av oppdrettsanlegg, naturskader, overbeskatning og multippelt stress på kystnære fiskebestander.
For å sikre videre oppfølging har HI besluttet at SalCod blir videreført i KystNord-satsingen (2025-2028). KystNord inkluderes også både i HI’s endringsprosjekt «CoastWatch», og i «Stor Satsing Kyst (2026-2029) – Styrket kystforvaltning av fiskeressurser og havbruk – kunnskap for balansert bruk, beskyttelse og restaurering i en natur og klimakrisetid». I så måte kan man argumentere for at nytteverdien av NFR-SalCod-plattformen allerede har vært betydelig, fordi det har flyttet fokus mot kystsonen, mot kunnskapshull i nord, mot spesielle sameksistensutfordringer mellom sårbare ressurser (kysttorsk inkludert), verneverdig natur og økende industrialisering, og til sist mot mangelfull overvåkning og forvaltning. Dette vil skape en ny, styrket og vedvarende aktivitet ved HI (2025-2030), som også var det overordna målet for NFR-plattform-utlysningen i 2018.
There are more than 1000 operational salmon farms along the Norwegian coastline, typically situated in fjords and often overlapping with the habitats of commercially and culturally important wild species. Despite the vast volume of salmon aquaculture in Norway, the full scope of its ecological impact is yet to be thoroughly investigated. In the proposed project, Impacts of salmon farming on Atlantic cod stocks (‘SalCod’), we aim to get a holistic view of the impact of salmon farming on wild Atlantic cod Gadus morhua populations in the Arctic region. To achieve this, we will use a suite of different approaches, including acoustic telemetry, mark-recapture studies, diet, growth- and maturation schedules and detailed examinations of juvenile habitat utilisation and associated benthic community structures. We will implement a before-after-control-impact (BACI) study design, working in northern Norwegian fjords with and without, and before and after, salmon farming over a five-year period. We will be able to quantify the impact of salmon farms on cod survival, growth, migration, spawning and recruitment, and collate this information in IBM and state-space models, allowing us to make broad inferences about the underlying mechanisms and identify the pressures from salmon farming on cod populations, how they vary interannually and upscale the results to the population level. This is at the heart of the Marinforsk Call.
