SYDNEY, Oct. 12 (Xinhua) -- Southern right whale numbers have boomed off the coast of Western Australia (WA) but researchers are unsure why.

Initial counts, conducted by citizen volunteers, show that whale numbers have more than tripled, local media reported on Friday.

"The southern right numbers are very different this year from our normal sighting rate of about 30 a season - this year we have over 100," Western Whale Research director Chris Burton said.

Numbers of the still endangered southern right whales have been steadily increasing for at least two decades, when Burton's land-based monitoring program began.

"Back when we began, southern rights were initially very rare, we'd probably see a dozen a season if we were lucky - this year is particularly interesting because the population of southern rights is generally based along the southern coastline of Australia," Burton said.

"As (population numbers) slowly increase, they may be spreading out towards areas they used to inhabit before whaling."

Historically the whaling trade, which ceased in WA in 1978, has been an immense pressure on right whales, even giving them their namesake because they were trusting and docile, making them the "right" whale to hunt.

Numbers are also on the rise for the immensely popular humpback species, which are a favorite among whale watching tour groups.

"Humpbacks account for about 90 percent of the baleen whales we see along this coast," Burton said.

"All these animals come down past this area from their breeding areas in the tropics, to their feeding areas in the cold southern ocean over summer."