Addressing the future of pink salmon in Norway

In recent years, the presence of pink salmon in Norwegian rivers has increased significantly. Hunters, anglers, and researchers alike are concerned that these non-native species could pose a major threat to native species and ecosystems. Furthermore, the fact that pink salmon decompose and eventually die during the spawning stage can lead to severe pollution of the rivers they inhabit.

However, before it spawns, it makes a delicious meal, which is why pink salmon in Alaska, Canada and Russia have long been economically important. It is caught at sea or immediately after returning to the river, and is considered a valuable food source.

“In its edible marine stage, it resembles Atlantic salmon,” says Dr. Simo Madonna, researcher at NIBIO Svanhovd. “Only after they begin their journey upstream in rivers do fish ready to spawn turn grey-brown, and males develop their distinctive hump.”

Dr. Madonna and her colleagues recently published a study on non-native Norwegian pink salmon. Through advanced modeling, they examined the river conditions in which pink salmon thrive, and investigated why they spread to new areas.

“The main factors that influence where pink salmon are located appear to be temperature and precipitation,” the researcher says. “In addition, pink salmon seem to prefer areas with lower elevation.”

The study suggests that the environmental condition in rivers that researchers have identified as particularly suitable for pink salmon is likely to remain relatively stable over the next 30 years. Therefore, Dr. Madonna doubts that we will be able to completely eradicate pink salmon.

“We need to find long-term post-control measures, as well as effective ways to utilize pink salmon as a resource,” he says. “Alongside local interventions such as traps and nets in estuaries, we should seriously consider using them as a food source. This approach could benefit our environment and Norway’s blue economy.”

Distribution modeling as a tool

The models used in the calculations are so-called species distribution models (SDMs). Environmental data, specifically weather and climate data, from rivers throughout Norway where pink salmon occur were used as input. River systems in which pink salmon had not yet been discovered were also taken into consideration.

Using advanced algorithms, the models were able to predict rivers and other areas with similar or better conditions to which pink salmon could spread.

“The models help us understand and predict where pink salmon may establish self-recruiting populations in the coming years. This is particularly useful in terms of where it may be necessary to implement proactive management measures that counter establishment in rivers that are both highly suitable and those that are not.” “It is still occupied,” says Dr. Madonna.

Northeastern Norway: Today's hotspot for pink salmon

Dr. Madonna found that northeastern Norway is the most important area for the spread of pink salmon, but there are rivers suitable for this species throughout the country.

“Norway has many areas with ideal environmental conditions for pink salmon. Today, the rivers in eastern Finnmark are the ‘hot spot’ of the surge, i.e. where pink salmon have become well established and spread from. Our models indicate that we will likely see new species of pink salmon.” Pink salmon shows that hot spots will be elsewhere in the coming years.

Models show suitable places for pink salmon beyond Norway's borders as well, including the UK and Iceland where pink salmon have already been discovered.

“Climate change could cause pink salmon to spread further south in Europe as well,” says Dr. Madonna. “However, we must exercise caution before drawing definitive conclusions, as there may be other important factors that the models have not yet taken into account.”

Genomics as a tool for understanding the spread of pink salmon

In addition to learning about the environmental and climatic conditions in which pink salmon thrive, researchers have developed a new genetic approach to study pink salmon in their non-native range, where all fish are more closely related to fish in their native range. . By analyzing DNA from pink salmon samples from 2019, they discovered river-specific genotypes and directional gene flow, suggesting important rivers for pink salmon that serve as a source of dispersal to other rivers in Norway.

The researchers now aim to incorporate genomics into their species distribution models. This will help them determine the timing and sequence of spreading events from current and future hotspots.

“The data we collected can also be used in future studies to see if the measures implemented to contain pink salmon are actually working as intended. It can also help us understand more about the life history of the species and its genetic characteristics in both regions,” says Dr. Madonna. Original and submitted.

The researcher is convinced that the ongoing research at NIBIO Svanhovd provides valuable insights for pink salmon management in Norway, and is grateful for the local support the team has received.

“Our research would not have been possible without the help of many dedicated people in East Finnmark who support and contribute to our work,” he says.

Facts about pink salmon (Oncorhynchus gorbuscha)

Pink salmon is a type of salmon originating from the Pacific Ocean. It was introduced to Russia in the 1950s and has since spread to Norway. It is now an established species in many Norwegian rivers, especially in Finnmark. It has been classified as an invasive alien species and has been blacklisted.

Pink salmon have a two-year life cycle, returning to the river in which they were born to spawn every two years. Its presence in Norwegian rivers is particularly high in odd years. In Norway, spawning is observed from mid-June to late July, with peak spawning in August and September. During the spawning period, males develop a distinctive hump on their backs. The color changes from silver in the sea to olive green/brown in the rivers as spawning approaches.

The typical weight of mature fish is around 2 kg, but they can reach 75 cm in length and weigh up to 6.5 kg.

To limit the spread of pink salmon in Norwegian rivers, measures such as traps and fishing nets are used. The timing of these measures is critical to prevent early and late spawning. There is also ongoing research to find the most effective measures to combat these invasive species.