Reports of unusually colored lobsters, including blue, orange, calico and two-tone varieties, have jumped in recent years. Researchers are unsure of the cause, although increasingly large harvests increase the odds of catching a quirky crustacean.

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 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.

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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 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.

“Are we seeing more because the Twittersphere 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?”

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.

Aside from color, the lobsters are apparently normal, Bayer said. They all turn red when they’re cooked, except for the white ones since they don’t have any pigment, and diners wouldn’t notice a difference.

“There’s no difference in taste,” he said.