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Like sequins on a ‘70s jumpsuit, the male rock greenling’s (Hexagrammos lagocephalus) scales shimmer in the light in all its rainbow glory. But far from standing out, this colouration can actually help this North Pacific fish hide. See for yourself – it’s on display in the Treasures of the B.C. Coast gallery at the Vancouver Aquarium.
Evan M., the Aquarium’s electrician, chose the rock greenling for June’s “Staff Pick of the Month” because the fish’s psychedelic colours and patterns got his attention. He sums it up by saying, “just look at this fish – it’s awesome!”
This fish sports what biologists call “disruptive colouration”. This is a type of camouflage that uses colours and patterns to break up the outline of the fish’s body.
This colouration makes it hard for predators (and prey) to see its shape, allowing the rock greenling to lay low among kelp and other algae until danger passes or, alternatively, to surprise an unwary prey.
Only the males are “dressed” like disco kings – females tend to be less colourful. Is a male rock greenling this brilliantly coloured to attract a mate, and does it use its colour to claim its territory? Possibly, since its colours fade in the winter when it takes a break from mating. But the truth is, we don’t know for sure. We know very little about the life story of this fish.
Evan also admires the rock greenling’s “toughness,” saying that it has to be able to thrive along the exposed west coast of British Columbia, where the water’s undercurrents are strong. This toughness also extends to this fish’s behaviour. Aquarium biologists call it a “badass” fish because it’s aggressive and has a propensity to attack other fishes that enter its territory.