PORTLAND, Maine >> When a 100-pound shipment of lobsters arrived at Bill Sarro’s seafood shop and restaurant last month, it contained a surprise — six orange crustaceans that have been said to be a 1-in-10-million oddity.

“My butcher was unloading them and said, ‘Oh, my gosh, boss, they sent us cooked dead lobsters,'” said Sarro, owner of Fresh Catch Seafood in Mansfield, Mass. “He then picked one up and it crawled up his arm.”

Reports of odd-colored lobsters used to be rare in the lobster fishing grounds of New England and Atlantic Canada. Normal lobsters are a mottled greenish-brown.

But in recent years, accounts of bright blue, orange, yellow, calico, white and even split lobsters — one color on one side, another on the other — have jumped. It’s now common to hear several stories a month of a lobsterman bringing one of the quirky crustaceans to shore.

It’s anybody’s guess why more oddities are popping up in lobster traps, said Michael Tlusty, research director at the New England Aquarium in Boston.

It could be simply because advances in technology — cellphone cameras and social media — make it easier to spread the word about bizarre lobster sightings.

It’s also likely more weird lobsters are being caught because the overall harvest has soared. In Maine, the catch has grown fourfold in the past 20 years, to nearly 105 million pounds last year. If the yield has quadrupled, it would make sense to have four times as many unconventional lobsters being caught as well.

Although lobster is the No. 1 commercial fishery in the Northeast, there are a lot of unanswered questions about the bottom-dwelling creatures, he said.

“Are we seeing more because the Twitter sphere is active and people get excited about colorful lobsters?” Tlusty said. “Is it because we’re actually seeing an upswing in them? Is it just that we’re catching more lobsters so we have the opportunity to see more?

“Right now you can make a lot of explanations, but the actual data to find them out just isn’t there.”

Lobsters come in a variety of colors because of genetic variations.

It’s been written that the odds of catching a blue lobster are 1-in-2 million, while orange comes in at 1-in-10 million. Yellow and orange-and-black calico lobsters have been pegged at 1-in-30 million, split-colored varieties at 1-in-50 million, and white — the rarest of all — at 1-in-100 million.

But those are merely guesses, and nobody knows for sure.