The invasion of Norwegian coastal waters and rivers by pink salmon will have negative consequences for biodiversity, the productivity of local salmon populations and for aquaculture. To reduce the magnitude of the pink salmon invasion, regional and international cooperation is needed.
This is the main message in the risk assessment from the Norwegian Scientific Committee for Food and Environment (VKM).
VKM has assessed the risk to Norwegian biodiversity, to the productivity of native salmonid populations, and to aquaculture, from the spread and establishment of pink salmon in Norwegian rivers, and has assessed mitigation measures to prevent the spread and establishment of this alien species.
The Norwegian Environment Agency and the Norwegian Food Safety Authority jointly commissioned the risk assessment.
Pink salmon is native to rivers around the northern Pacific Ocean. Russian authorities’ efforts to establish this species around the Kola Peninsula in the second half of the 19th century resulted in pink salmon finding its way to Norwegian waters. Pink salmon has been observed in rivers in eastern Finnmark for many years, predominantly in odd-number years when they migrate up the rivers to spawn.
The extent to which pink salmon will affect the biodiversity and ecosystems in Norway depends predominantly on how many fish there are.
“Thousands of spawning pink salmon will have a major effect on our local salmonids, on water quality, and on biodiversity both in the water and on land,“ tells Kjetil Hindar, academic leader of the project group.
“The pink salmon will produce millions of fry that will compete for food and space with the fry of our local salmonids. Pink salmon will reduce the number of small crustaceans and insects when foraging, “ he explains.
Coastal and oceanic ecosystems will be affected.
A large population of pink salmon will increase the likelihood of pathogens being spread to both farmed and wild Atlantic salmon.
It appears that pink salmon in the North will have a greater chance of surviving with increasing sea temperatures. The likelihood of the species survival and establishment will probably be increased by the ongoing climate change.
“A warmer climate can lead to unexpected interactions between pink salmon, pathogens and other species. In the last years the sea surface temperature has increased dramatically. This means that when considering future development for the species, we’ll have to account for unprecedented scenarios regarding ocean conditions. This may be our greatest challenge,” says Hindar.
One mitigation measure proven to be effective in reducing the negative impact on biodiversity is targeted fishing of pink salmon. This can be done using baited rods, harpoons, nets, traps, as needed for to the local conditions of each river. To reduce the number of pink salmon in the ocean, and to prevent invasions of spawning fish in our waters, collaborative efforts are necessary regionally, nationally and internationally, concluded VKM.
The risk assessment is based on a thorough literature search, and on consultations with scientists in North America, Western Europe, Russia and Norway. In Norway, the team had discussions with environmental departments in Troms and Finnmark counties, with local fishing associations, landowners and other interested parties.
VKM has investigated whether the sea surface temperature (SST) has any effect on the amount of surviving pink salmon fry, and whether an increase in SST correlates with an increase of returning adult pink salmon.
Risk is determined by the magnitude of the potential impact, and the likelihood of whether this event occurs. The project team emphasizes that some of the evidence is considered to have low certainty, because of the lack of peer-reviewed publications and studies about Norwegian conditions.
The risk assessment has been approved by the VKM Panel on Alien Organisms and Trade in Endangered Species.