Researchers say a young member of an endangered killer whale population living off British Columbia's coast has died.

The Washington state-based Center for Whale Research says J52, a male southern resident killer whale, was last spotted near the Strait of Juan de Fuca south of Vancouver Island on Sept. 15.

The two-and-a-half-year-old whale appeared lethargic and was barely surfacing, with photos showing signs he was malnourished.

southern resident baby orca

J52 is seen surfacing off San Juan Island, Washington in 2015. (Capt. Gary Sutton/Ocean EcoVentures Whale Watching)

Researchers with the centre say the Chinook salmon the orcas eat have been in short supply this year.

J52 was not spotted when his pod was observed in Puget Sound off Washington state on Sept. 19 and the centre says he presumably died of malnutrition hours after he was last seen.

The scientists say there were 78 southern resident killer whales as of last December, and the centre has warned that noise, toxic contamination, and a lack of food threaten their long-term survival.