Pink salmon

The amounts of pink salmons have increased explosively during the last years. In river Tana the number of individuals have increased in a few years from a few hundred individuals to an estimated 100,000 – 150,000 individuals in summer 2023. The impact on the biodiversity is unknown, but pink salmon might be a threat for the indigenous salmon. Every pink salmon dies after spawn which releases huge amounts of nutrients into the rivers. We still don’t know how these new nutrients will affect our ecosystems, which tends to be poor of nutrients.

Basic info

Common name: Pink salmon

Scientific name: Oncorhynchus gorbuscha

Pink salmon has always a 2-year life cycle 

Official establishment classifications of pink salmon vary from country to country. In practice pink salmon seems to be established in several rivers draining into the Atlantic Ocean, and the number of spawning individuals is constantly increasing. 

The pink salmon, also known as the humpback salmon, is 45 to 65 centimeter long and weights 1 to 3 kilos. The life cycle of the generation is always two years, and individuals die after breeding. Pink salmons born in odd years do not spawn or interbreed with those born in even years. In Norway and Finland, the odd year populations have increased explosively. During the summer 2019 an estimated 5000 pink salmon migrated to river Tana to spawn. In summer 2021 there were 50 000 pink salmons, and the next estimated mass migration will be in summer 2023. The population size during the even years have remained small. 

The pink salmon males develop a hump on their back and a hooked chin during the breeding migration when they return from the sea to rivers to spawn. Spawning season is from July to September, and the juveniles migrate to the sea during their first summer when they are from four to five centimeters long. The adult pink salmons die right after spawn. 

Prevention is still being developed

It is unsure how severe the effect will be on our northern ecosystems. Since every pink salmon dies after spawning, energy and nutrients are released to the river ecosystem. In the original distribution areas pink salmon has a significant role in the energy flow. We still don’t know how these new nutrients will affect our ecosystems, which tends to be poor of nutrients. 

As often with new invasive species causing troubles there is no ready solution how to solve the situation. Trapping and fishing methods is being developed both in Finland and Norway. In this project we develop different ways of catching the pink salmon. They will be tested in real action during the pink salmon mass migration in summer 2023. A seine is developed from a traditional salmon seine. Also a new kind of drift net meant to be used in very low water is developed for catching pink salmons arriving for spawn. In Norway there is even plans for damming up whole rivers with special dams that would let other fish species pass it but would stop the migration of pink salmons. If a private person catch a pink salmon it should be removed, not released back to the water. 

How to tell the pink salmon from Atlantic salmon (Salmo salar)?  

Pink salmon can be distinguished by the large dark oval spots on their back and small scales. During the breeding season the males are easily recognized by the hump on their back. 

More about pink salmon

Briefly about pink salmon -video

See how a dragnet is tested in our project in river Tana! Videos by @VeVetsi.

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