Three killer whales from Washington State’s well-known Southern Resident Killer Whale (SKRW) group are presumed dead after missing all summer, dropping the total population to 73 as of last month.

“We are saddened to report that three adult killer whales (orca) are missing and presumed dead as of July 1, 2019,” said the Center for Whale Research in a statement. “These whales are from the extremely endangered Southern Resident killer whale population, that historically frequent the Salish Sea almost daily in summer months.”

The SKRW clan is one of two orca communities that live in the Puget Sound area of Washington State at the boundary of Canada and Washington. This time last year, the Center for Whale Research reported the population had dropped to a 30-year low with just 75 members after a three-year period in which scientists did not record a single calf. A number of international initiatives have been set forth by both the US and Canadian governments in order to help the ailing whale populations, including halting a major pipeline expansion project that had the potential to cause further harm to the ailing population.

Scientists believe a number of factors are at play, including the amount of underwater noise and vessel-strikes in the traffic-heavy waters of Puget Sound, as well as increasing population pressures from disease, catastrophically low birthrates, and an increasing lack of primary prey.

“Due to the scarcity of suitable Chinook salmon prey, this population of whales now rarely visit the core waters of its designated Critical Habitat: Puget Sound, Georgia Strait, and the inland reach of the Strait of Juan de Fuca,” said the center.

The three missing orcas are J17, K25, and L84 whose names correspond to one of three pods (J, K, and L) in the region to which they belong.

Forty-two-year-old matriarch, J17, is the mother of Tahlequah (J35) who was made famous last year after carrying her dead calf for a record-setting 17 days last summer. Researchers at the center spotted J17 last winter in poor body condition they believe was possibly caused by stress. Her two daughters and son – J35, J53, and J44, respectively – are still alive and have been spotted in the J pod this summer.

An adult 28-year-old male who the center says was in the “prime of his life” is also presumed dead after scientists last saw him in poor body condition last winter. His two sisters and brothers – K20, K27, and K34 – are all living in the K pod.

Lastly, a 29-year-old male, L84, is presumed dead after the Canadian Department of Fisheries and Oceans report they have not seen the whale during their summer surveys along Vancouver Island. L84 is the last of a matriline of eleven whales that have previously died. The L pod have not yet been reported in area waters this summer.