© David Ellifrit/Center for Whale Research via APA critically endangered orca is presumed dead following a six-month span without a single sighting, according to a nonprofit dedicated to saving the species.The orca, of the Southern Resident population and named L41 Mega, was not seen with his family on Jan. 24 off Washington's coast, according to Shari Tarantino, president of the Orca Conservancy.Tarantino said the last time L41 was seen was in August 2019. "I hope he comes back, but I don't think so," she told ABC News on Thursday.The presumed loss of L41 is the latest difficulty facing the dwindling population.L41 was among two orcas who fathered a majority of the population's offspring. The orca J1, who is dead, fathered 16 of the Southern Residents, while L41 fathered 20, according to the NOAA.Tarantino believes that L41 was post-reproductive, but said he was "still a vital member. ""It's kind of like us," Tarantino said. "We take care of each other.