Neon green pike's colour is adaptation, not mutation, experts say

A fluorescent green jackfish caught earlier this week made quite a stir online as readers debated the origins of its odd colouration, but two pike experts say the answer is likely simple biology.

The pike, which hada bright green body and blue throat, as well as aneon green tint across its jawline, was caught by Yellowkniferesident Randy Strakeron Sunday. Straker, who caught the pike in the North Arm of Great Slave Lake, released it after taking a few photos, leaving nothing but pictures, and a fishy mystery.

• Fish mystery:Neon jackfish leaves Yellowknife fisherman stumped

Jeff Goudreau, a fish and wildlife technician and fishing guide who worked on Great Slave Lake for years, said he recognized the colouring right away.

"I've probably caught threeor fourof those in my life," he said."And I know a lot of other guides in Canada in other lakes that have caught similar ones."

According to Goudreau, the pike's unique colouring is due to a type ofcell that gives all fish their colour, called chromatophore.

Chromato-what?

"Most people understand chromatophores from seeing cephalopods in the ocean, like squid or whatnot," explained Goudreau."They change colour when they're scared, or they're getting ready to attack something. Pike do the same kind of thing, but on a lower level."

Goudreau said that this pike's unique colourationwas likely due to the fact that it spent its time hunting near the surface of the lake where the sun is brighter and the water colour a lighter blue and near reeds, whichare oftenhavens for green algae growth.

"They try to blend themselves into that environment to be better hunters," he said. "So you'll see those aquamarine colours, where the throats are very blue and dark green and stuff.That's pretty much what's happened, with that one."

Neville Fickling, a zoologist from England who's written multiple books on pike, agrees with Goudreau's assessment, saying that the fish are "always going to determine exactly whattheir environment is, and adapt the chromatophores accordingly."

Although all fish regulate their colouration using chromatophores, some fish have the ability to change colours more quickly or intensely than others.

"Discolouration, which is the degree of change from dark to a light, or a brown colour to a green colour, that's very common," said Fickling.

"A common trick that we do in England is when we catch live fish for bait, you put them in a white bucket, and they become much lighter in colour, because they're adapting to the environment."

Goudreau said that he's caught pike of other shades in Great Slave Lake, including vibrant brown fish in dark water "where there's tons of old logs."

Because of its size its the tenth largest lake in the world and the deepest lake in North America Great Slave Lake is one of the best places in the world to see different variations of pike, he said.

Colouration vs. mutation

Pollution or radiation from Fukushima was a common reason suggested by readersfor the neonpike's colour, but while its green tint is likely due to a need to adapt for hunting purposes, there arealso genetic mutations of pike in the lake.

"There's two aspects to this," said Fickling."One is just basic shading, as opposed to marking change. It's important that we look at the two things separately. Markings spot markingsthose things are genetically brought about."

Great Slave Lake is alsohome to silver pike, a genetic variation of northern pike that takes on a shiny silver tint. Unlike Straker's green fish, though, silver pike have a different scale pattern, with much smaller spots that sometimes run from top to bottom, instead of from front to back.

Fickling also pointed out that a small number of golden pike have been seen around the world, which he said were simply "freak" a result of a genetic anomaly.

Fears that the neon fish resulted fromradiation fallout from Fukushima or arsenic tailings from Yellowknife's nearby gold mines were "funny," Goudreau said. "If you didn't understand it, then that's what you'd think."

But he's clear: there's no specific toxin that would have caused the colouration.

"It's just about math, man.Statistics. When you have that many pike ... you're going to have all these different variations," he said.

"It's actually a pretty awesome thing."