A team of researchers spent eight years counting the humpback whales returning every summer to feed around Gil Island and the channels leading to Kitimat, B.C. The whales are considered a threatened species due to commercial hunting before 1966. According to the study published last week in PLOS ONE, the number of whales has increased over the research period, despite major shipping routes crossing the region.

Kitimat is a major port for oil and Liquefied Natural Gas tankers bound for international markets. It’s also where the Northern Gateway Pipeline is proposed to carry bitumen from Alberta.

“These whales are traveling, feeding or resting on the surface,” say Janie Wray and Hermann Meuter, founders of the North Coast Cetacean Society and two of the study’s authors. “There is no room whatsoever for a tanker to pass without a whale being in its path.”

The team, including Erin Ashe and Rob Williams from the University of St. Andrews in Scotland and the Gitga’at First Nation’s Christopher R. Picard, set out to estimate how many humpback whales use the area. To make sure they weren’t counting the same whale multiple times, they took pictures of the underside of the whales’ tail flukes, which could be used to tell individuals apart. They ended up with 177 high quality photos of clearly different whales.

The researchers estimate that the number of humpbacks that come to the area has roughly doubled to 137 since 2004.