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

A fluorescent green jackfish caught in Yellowknife's Great Slave Lake 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.

Fish changed its colour to become a better hunter, say fish technician, pike author

Randy Straker's jackfish was like 'nothing he'd ever seen,' but a Great Slave Lake fishing guide says he's caught 3 or 4 fish with similar colouring, in a similar part of the lake. (submitted by Craig Thomas)

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 had a bright green body and blue throat, as well as a neon green tint across its jawline, was caught by Yellowknife resident Randy Straker on 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. 

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 three or four of 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 of cell that gives all fish their colour, called chromatophore.


"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."
The blue and green shades in the pike's mouth and throat are likely an adaptation to hunting near the surface of the water, where the colour is brighter, according to two experts. (submitted by Craig Thomas)

Goudreau said that this pike's unique colouration was 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, which are often havens 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 what their 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 readers for the neon pike's colour, but while its green tint is likely due to a need to adapt for hunting purposes, there are also genetic mutations of pike in the lake.
Jeff Goudreau, left, poses on Great Slave Lake with a 'normal' northern pike, while a friend poses with a silver pike, which is a mutation. Shading is simply due to chromatophore, explained Goudreau, while marking changes, such as on the silver pike, are due to changes in the fish's genes over time. (Submitted by Jeff Goudreau)

"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 markings — those things are genetically brought about."

Great Slave Lake is also home 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 from radiation 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."


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

Become a CBC Member

Join the conversation  Create account

Already have an account?