Case Study 6 – Pink salmon

Case Study 6: Pink Salmon

(Oncorhynchus gorbuscha)

Description

Pink salmon, also known as humpback salmon, is a fish species native to the American Pacific coast. They are anadromous and semelparous fish, spending most of their time in the ocean and ascending rivers during the breeding season after which they spawn and die. Spawning happens in a two-year cycle, meaning that they become more abundant in odd years. Juvenile pink salmon migrate to the sea where they graze and feed on other fish and invertebrates such as krill and amphipods. During their second summer, they are ready to spawn and return to the rivers to complete their life cycle.

Pink Salmon share the same habitats and niches with other salmonids and fish. Recently, they outnumbered native anadromous salmonids in many rivers in northern Norway, and 2023 marked the first year they outnumbered Atlantic salmon (Salmo salar) in abundance and biomass in the catch of commercial fisheries in Norwegian fjords.

Habitat

Pink salmon live along the coastline or reside in rivers and lakes at different life stages. They were introduced to the White Sea area and Kola Peninsula in Russia in the late 1950’s as a possible fisheries resource. Since then, they have spread through the Barents Sea and the North Atlantic Ocean to new territories within Britain, Iceland, Norway, Sweden and other countries. The first occurrence of pink salmon in Norway was observed in the 1960s. Since then, the population in Northern Norway has been growing, especially after 2017.

Impacts

Biodiversity: In their native environment, pink salmon are highly competitive over food resources with other salmonids and fish in both marine and freshwater environments. Out of their native environment, large schools of pink salmon may disrupt native salmon populations. In Norway, pink salmon smolt have an adaptive value as prey for other salmonids, and adult carcasses can serve as food sources for terrestrial and aquatic predators.
Water Quality and Ecosystem Shifts: Pink salmon die after spawning, and as such, their decomposing carcasses release large amounts of nutrients in the water. Long term persistence may create hypoxic conditions and as such lead to a pollution problem. The mass mortality of thousands of fish after spawning creates a surge of marine-derived nutrients that can degrade water quality, cause offensive odors, and attract scavengers, fundamentally shifting the natural energy flux of both aquatic and terrestrial ecosystems.
Disease Vector: Pink salmon is likely to spread fish pathogens such Gyrodactylus on wild and farmed salmon.

Prevention and Control Actions

While total eradication is unlikely given how well-established the species has become, the GuardIAS project is focusing on controlling populations, improving detection, and better understanding pink salmon impact on ecosystems.

Improved Detection: Researchers will monitor the relative abundance of pink salmon carrion along river systems with different management regimes by combining traditional count surveys and environmental DNA (eDNA) surveys. The eDNA surveys will include both eDNA samples and a novel sampling technique: DNA derived from carrion flies through insect DNA (iDNA).

Predictive Modeling: Researchers are developing methods to predict where the fish will be located, allowing authorities to implement traps more effectively before spawning occurs.

Stakeholder Engagement: GuardIAS is conducting a wide-reaching survey involving ecologists, salmon farmers, fishers, and government agencies to assess how the species is perceived and to determine the most effective economic and ecological management strategies for Europe.
Risk Analysis: A bow-tie analysis is being used to visualise the risks, as well as the potential ecological and economic consequences, associated with the spread of pink salmon in northern Norway.

Useful links

Meet the case study team

Nord Universitet: Joost Andre M. Raeymaeker, Amalia Mailli, Sam Steyaert, Bror Matthias Bonde, and Mark Costello

Case study contact: Joost Raeymaekers, joost.raeymaekers@nord.no

Anastasija Zaiko

“This project is not just about managing invasive species today—it’s about developing a proactive approach that anticipates future ecological challenges, ensuring robust ecosystems and sustainable marine environments for generations to come”

Sergej Olenin

“For over 35 years, since I first began studying non-indigenous species, I have dreamed of tools that could reveal the ‘Big Picture’ of the transfer, spread, and impacts of invasive aquatic species. Thanks to advances in new technologies, the GuardIAS project now offers an outstanding opportunity to make that vision a reality.”

There are 7 Work Packages (WP) focusing on different stages of invasive alien species ‘invasion’ in the GuardIAS project. Each Work Package is a distinct project area, but all are interlinked through GuardIAS as a whole.