A 43-year-old male orca named Mega, now missing and presumed dead, was one of the first new calves that researcher Ken Balcomb spotted when he began his extensive census of Southern Resident killer whales back in 1976.

Ken didn’t know it at the time, but the baby orca — one of nine born in 1977 — would grow to become a large, powerful whale, living up to his name by fathering at least 20 offspring of his own.

Designated L41, Mega was around throughout Ken’s career at the Center for Whale Research. Ken watched other baby orcas grow up and eventually die, with many perishing before adulthood. The average lifespan of a male resident orca was once calculated at 29 years old, Ken told me, though it may be less now.

Several years ago, Mega seemed near death, Ken said. “He was lethargic and breathing hard and was away from the other whales by a couple miles. We thought that was it for him.” But the next time his group of whales came around, he was doing much better.

Last Friday, Mega was missing from his social group, known as the L12 subpod. Orca researcher Dave Ellifrit got a good look at the group, which is rarely seen in inland waters. Mega’s large, distinct dorsal fin provided a first sign that observers could use to identify the group. The aging male was looking rather thin a year ago, Ken said, and now all signs point to his death. Read the Center for Whale Research encounter from last week.

“We are hopeful that L41 is alive somewhere and returns to the subgroup, but he did live to a ripe old age and fathered more baby whales than any other whale in the community,” Ken wrote in a note of reflection on the Center’s website.

“We watched the energetic young male baby as he grew up, and we had great hopes that he and his companions would fill in the youthful cohorts of the population that had been decimated by captures between the mid-1960s and mid-1970s,” Ken wrote.

“To me, he was not particularly noticeable for his behavior,” Ken told me on the phone. “Until the genetic work, we never realized that he was quite a loverboy.”

A genetic study led by Mike Ford of NOAA’s Northwest Fisheries Science Center found that two whales — Mega and Ruffles (J1) — were responsible for 80 percent of all the paternities where a father was identified. Mega produced 20 known offspring, of which 14 are still alive. Ruffles produced 16 known offspring, of which 12 are still alive. A few other males added one or two offspring each to the population.

Ruffles died in 2010 at an estimated 59 years old.

Mega’s death would bring the Southern Resident population to 72 whales, just one higher than the 71 orcas counted during Ken’s first survey in 1976. It was a year of recovery following the halt of a massive capture of whales for aquariums around the world.

In the early months of that first survey, Balcomb, along with the late Mike Bigg and others, identified the Southern Resident killer whales for the first time, using their unique markings, including a “saddle patch” behind the dorsal fin. The researchers assigned them to one of their three major groupings, J, K and L pods. They also assigned numbers in the order they were first identified.

After the first year, the numbers were assigned in order that the whales were born. Thus L41, later named Mega, was among the first nine calves to receive their numbers along with a precise birth year. Of those nine whales, three are still alive: L54 or Ino, a female who has three living offspring; L55 or Nugget, who has four living offspring; and K14 or Lea, who has three living offspring.

Mega was unusual in that he lived many years after the death of his mother in 2000. Often, males survive only a year or two after their mothers are gone, presumably because older females share food with their more energetic male offspring.

As for Mega, he will be missed, but as Ken wrote, “He had a good life.”