Trout sponsored by Helsingin Sanomat fitted with radio transmitter

Movements of the fish to be monitored over the coming months

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If Monday’s experiences are anything to go by, the southern River Vantaanjoki is rich in trout and salmon. In less than an hour, a crew of two men removed four 5-kg trout from their nets in the vicinity of the Vanhankaupunginkoski rapids.
      These fish have a mission. They were fitted with radio transmitters next to their dorsal fins. The apparatus allows researchers to follow their movements as they rise up the river to their spawning grounds.
      The transmitter and its thin 20-centimetre antenna has not been found to inconvenience the fish. “They behave normally”, affirms researcher Ari Haikonen.
      The radio fish have sponsors, who pay EUR 2,800 for the transmitters. The money goes towards work promoting the Vantaanjoki.
      The undertaking is administered by the Pro Vantaanjoki Organisation, with Haikonen and historian Jukka Relander as its contact persons. Forty transmitters have been reserved for the project and there is still room for additional sponsors.
     
After disentangling the trout from the net, water-bailiffs Mikko Karvonen and Jyri Tiemaa placed them into a fish chest on the shore, from which they were netted into an anaesthetisation pool. Researcher Petri Karppinen then fitted the trout with the transmitters, after which the perplexed fish were released back into the river to wonder what in the world had just happened to them.
      While at it, the researchers also measured and weighed the fish and took scale samples.
      The trout sponsored by Helsingin Sanomat was the first one to emerge from the fish chest. Karppinen examined its shape and fins. “Looks good”, he said.
      The male trout weighed 4.8 kilograms and was 71 centimetres long. At 11.25 a.m. it set of in a slow and dignified fashion to swim towards quieter waters and ponder things.
      The scale sample later revealed that the fish had had a three-year smelt phase in the river, followed by another three years in the sea.
     
In the first instance there was no perception of the HS trout’s presence from the transmitter, but in front of the rapids there is a six-metre-deep bowl from the depths of which the signal cannot be detected. We have to assume the fish was down there somewhere, planning its next move.
      The movements of the trout in the 100-kilometre Vantaanjoki will be followed by using a portable device. In the Vanhankaupunginkoski rapids and the Vantaankoski rapids a little further north there are permanent receivers. In the coming days the fish can also be followed on the Internet at www.radiokala.net .
     
     
Readers of Helsingin Sanomat are also invited to come up with a name for the fish, which should be trackable for three or four months, until the battery in the transmitter runs out.


Links:
  Vantaanjoki (Wikipedia)
  radiokala.net (in Finnish)

Helsingin Sanomat