An orca whale is missing and presumed dead, bringing the local killer whale population to its lowest point in three decades.

The Center for Whale Research said Saturday an adult male known as L92 has not been seen since November 2017 and was “conspicuously absent” from recent coastal sightings of other whales.

The whale, nicknamed Crewser, was 23 years old.

The animal was a member of the L pod — the largest of three groups, along with the J and K pods, that make up the southern resident group of killer whales, which typically travel between the inland waters of Washington state and southwestern British Columbia for most of the year. It was the second-to-last member of the L26 matriline — the only surviving whale is now its aunt, known as L90.

The loss brings the total southern resident population of orcas down to 75, the lowest since 1984. The population has fluctuated in recent decades, reaching a peak of 98 whales in 1995. Just two years ago, there were 83 orcas here.

Whales in recent years have died from various causes, including malnourishment, infections and being struck by boats. Researchers say the decline of chinook salmon — the whales’ main prey — has contributed to the deaths, as have vessel traffic and noise. They have been listed as endangered species in the United States since 2005.