Tens of thousands of humpback salmon are currently spawning in the coastal shallows of Tenojoki. HS watched as the researcher descended to film the commotion.
Tenojoki in the shallow coastal water, the female humpback covers her spawning hole. A new generation of humpback salmon has begun.
When one pit is covered, the female continues to dig the next one. It digs a hole with its tail, and when it starts to lay its roe eggs, the dogs waiting next to it rush to spray them with food.
On a sunny August evening, Tenojoki is bustling.
Humpback salmon dogs (front) wait near spawning females. They hope to be able to spray milk on the roe’s eggs.
Humpback salmon dogs have gathered in one group.
Only the male has a hump, the female does not.
August on a warm day in the evening, Tenojoki makes its peaceful but rapid journey towards the Arctic Ocean. The current lapping at the beach stones. A dark figure glimpses in the brown but clear water, then another, third, fourth, fifth. In the distance, it’s splashing. A dozen humpback salmon are easily landed within a radius of a couple of meters.
“The humpback salmon’s spawning pit is surprisingly deep, 20–30 centimetres,” says a researcher from the Finnish Natural Resources Agency Panu Orell in his wet suit. He is going to photograph the spawning humpback salmon.
“There you can see spawning pits, tubes like that,” he points to the bottom.
The female humpback salmon timidly defends her spawning partner. “It does drive the other female away,” says Orell.
When Orell has got his camera to the bottom of the river, one female will come and take a look at it.
“It might see its reflection in it,” Orell thinks.
Panu Orell, a researcher at the Norwegian Natural Resources Agency, went down to the water to film the spawning of the humpback salmon.
The beach humpback salmon remain in the current, lazily swimming in place, in a loose group. Dark fish have large white areas.
“Those are dogs, they’re waiting there, if you could have a little peek at the food,” says Orell.
Only a dog bears the hump that gave it its Finnish name. The female, on the other hand, shows the English name best pink salmon gave a pink tint on the sides.
“Those dogs are already at the end of their lives,” says Orell. Skin and flesh have come off, some are missing their entire hump and bare reeds are sticking out of their backs.
Humpback salmon die after spawning. “Dogs usually have a hump, females often have a tail,” says Orell. Humpback salmon invests everything in reproduction and sacrifices its own flesh to produce gametes. They still try to get to the spawning grounds, even without a tail.
Orell floats downstream in his wetsuit, sweating along the shoreline. The water is exceptionally high for the time. Unlike Teno’s salmon, humpback salmon spawn in the coastal shallows, mainly at a distance of about 10–15 meters from the shore. Teno has a lot of suitable gravel and small stone bottom.
“A couple of years ago, there were about a thousand humpbacks spawning here, now there may very well be a thousand,” Orell estimates. A total of around 100,000 Norwegian salmon dams have come up to Teno this summer to overtake the successful humpback salmon.
The Norwegian dam construction to remove the alien species humpback salmon has been placed in Norway below the Tenojoki bridge.
In gravel chicks develop in shelter and safety.
A female can produce thousands of rotten eggs. Not all eggs end up in the spawning pit, but when the female covers the pit, some of the eggs can be carried away by the current. They are nutrient-dense fins for whitefish, grayling, whitefish and Teno’s salmon fry.
“Regarding Teno’s salmon, it is often said that walleyes, graylings, trouts and whitefish eat their rotten eggs, but no critter from that gravel gets them. Those rotten eggs that are swept away by the current would be doomed anyway,” says Orell.
With the Norwegian dam structure, Kim Laxström moves humpback salmon towards the processing line.
Humpback salmon are stunned.
After being electrocuted, humpback salmon are bled and transferred to transport containers.
Natural Resources Center at the research point, 55 kilometers upstream from the mouth of Tenojoki, humpback salmon started to ascend on June 20. The hiking peak was between the 10th and 15th. July. The first humpback salmon spawn at the end of July, and now at the beginning of August, spawning is at its peak.
Soon it will start to decrease. Some of the humpback salmon hatch in October and spend the winter in the gravel. Chicks of humpback salmon spawned in September hatch in the spring. In May–June, the chicks emerge from the gravel into the open water and wander into the sea in their first summer. In the river, they eat small organisms in the water and bottom, such as plankton.
In Tenojoki, humpback salmon spawn mainly in different places and at different times than Teno’s salmon.
“In a big river, salmon spawn mainly in the middle bed, in the deeper water,” Orell points out. “The situation is different in small side branches.”
Humpback salmon spawn up to two months earlier than salmon. “Therefore, the humpbacks do not get to dig open the spawning pits of the salmon, but rather the other way around,” states Orell.
Because salmon and humpback salmon hatch at different times and humpback salmon fry quickly move to the sea, food competition between humpback salmon and salmon fry can occur mainly in the sea.
Onshore no humpback carcasses visible, only one loose head. “The current probably transports them, and they can accumulate in the area of the slower current,” Orell reflects.
Tens of tons of fish meat in a barren river is a big change, the effects of which on the river’s biological community are currently being studied.
“Nutrients can also benefit salmon fry, for example,” adds Orell. A large number of rotting fish may increase the bacteria concentration in the water. According to Orelli, if fish carcasses accumulate disturbingly on the beach, they can be disposed of by burying them one meter deep.
Humpback salmon spawned today can return to Teno to spawn.
“The humpback salmon is basically loyal to its home river, but it also gets lost easily and can quickly settle in new areas,” states Orell.
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