A blue salmon was caught yesterday in the river Elliðaá, in the Reykjavík area, by amateur fisherman Rögnvaldur Geir Sigurðsson. The fish had garnered attention for its unusual color earlier this summer when it was spotted in the river by fishermen and passersby.
“I noticed it right away, that this was that fish. It was azure almost, very beautiful. I have been fishing all my life and never seen this before,” said Rögnvaldur in an interview with RÚV.
The fish weighed about three pounds and the color, intense when it was first caught, faded as the day went on.
“Control of pigmentation appears to be very universal with salmon, with only the occasional one differing from the rest, so perhaps this is a result of some sort of misfiring with the system. It’s somehow connected to the eye, for instance blind salmon are black,” biologist Jóhann Sturlaugsson said.
Additionally, Jóhann said that often the color of the fish is also somewhat controlled by its environment. For example, farm-raised salmon kept in green containers often have a green tinge to them. “This one has hardly grown up in a blue tub though,” Jóhann added.
Björn Þrándur Björnsson, professor of fish biology at the University of Gothenburg, believes that it is the result of improper developments in the pituitary gland. The phenomenon is known among rainbow trout, where specimens lacking the hormone MSH due to the immaturity of the gland, lack proper pigmentation and are as a result pale blue in color. Although this happens with rainbow trout it is very rare and Björn has never heard it occurring in salmon before, mbl.is reports.
At least in rainbow trout it appears that this is not a genetic defect, but rather a sporadic mutation. “So you can probably not breed blue salmon, even if you wanted to, at least not at the moment,” Björn said.
Click here to view a video of the fish.