A pale killer whale has been spotted in the waters off Vancouver Island鈥檚 eastern shores after more than a decade without any sightings of an orca with such colouring.

Val Waston, a marine naturalist at Vancouver Island Whale Watching, was one of the lucky few who caught a glimpse of the young greyish-white calf with its eight-member pod on Tuesday.

鈥淲e thought it might be a trick of the light, but then as we got in a better position alongside them, it was indeed a white orca, which is incredibly rare and really amazing to see,鈥 she told CTV News Vancouver Island on Thursday.

So rare, in fact, that the last time a white killer whale was seen off the coast of British Columbia was 10 years ago. In that case, the calf died within its first year.

The first documented sighting of a white orca in British Columbia was in 1924, according to Jared Towers, an orca ecologist with Fisheries and Oceans Canada. He said there were a few more cases in the 1940s and 1950s.

In 1970, Towers said a white killer whale was captured in the waters off Victoria, B.C. and transferred to an aquarium in the city where it died. Since then, confirmed sightings of white orcas have been few and far between.

That is why Towers said this recently spotted whale is such a treat for the public.

鈥淭hat this animal is out there, it鈥檚 alive, and that people can see it, I think is a rare opportunity for people,鈥 he said.

The whale鈥檚 unusual bleached colour remains a mystery to marine scientists who have proposed several explanations for it.

Towers said it鈥檚 possible the young calf has a rare disorder called Chediak-Higashi syndrome, which was responsible for killing the white whale in 1970. The syndrome can affect the mammal鈥檚 immune system and cause partial albinism.

The orca ecologist said it鈥檚 more likely, however, that this young killer whale is 鈥減erfectly healthy.鈥 He said the orca may have a condition called leucism, which causes a partial loss of pigmentation.

Another possibility is that the young whale will lose its white colour as it ages and develop normal colouring, according to Towers.

鈥淭here have been a couple young killer whales documented that when they were born they were a lot lighter coloured and over time they grew up to be just a regular black and white colour,鈥 he said.

Regardless of why the young calf is the colour it is, Towers said he suspects this won鈥檛 be the last time they see the whale.

鈥淚鈥檓 sure this little family of whales will be seen numerous times over the year and we can keep pretty good track of this little animal,鈥 he said.

Towers said there is a good chance this killer whale will survive because it belongs to the Biggs killer whale population, which is thriving in British Columbia with numbers in the hundreds and most of the calves reaching maturity.

With files from The Canadian Press