The lobster is in its boom years on the Maine coast, and no one knows precisely why, scientifically speaking, or how long the boom will last.

Maine lobstermen had a record year in 2014, hauling in $456.9 million worth of the popular crustacean. While the actual amount of lobster landed was slightly below 2013 totals — 123.7 million pounds in 2014, down from 127.8 million a year earlier — the value of the catch shot up 23 percent.

Throughout the history of Maine’s lobster fishery, the total catch has never been as high as it has been over the past five years. In the 1960s, the annual catch hovered around 20 million pounds, according to the Department of Marine Resources. It wasn’t until 1991 when the fishery cracked the 30 million-pound mark. It cracked 40 million in 1997, then 50 million in 1999. In 2002, lobstermen hauled in 63.6 million pounds, and that high mark is only about half what today’s lobstermen catch.

“The lobster industry is an enigma,” said Brian Beal, a professor of marine ecology at the University of Maine at Machias and a former lobsterman. “It’s an enigma biologically, and it’s an enigma historically.”

There are factors that can explain growth in Maine’s lobster population, but nothing that definitively explains today’s lobster boom. Similarly, there’s limited insight into how long these lobster bounties will persist.

“We should know a lot more about the answers to why we are where we are and how long it will last,” Beal said.

Here’s some of what we do know:

Lobsters thrive in cold water, and they’re thriving in the Gulf of Maine even though it’s an epicenter for oceanic warming. Since 2004, the Gulf of Maine has warmed faster than 99.85 percent of the world’s oceans, according to Andrew Pershing, chief scientific officer of the Gulf of Maine Research Institute.

Fishermen have noticed the effects of a gradually warming ocean for a while. While a number of cold-water species — cod, haddock and shrimp, for example — are increasingly off-limits to fishermen, those who depend on the ocean for a living are noticing warmer-water species flowing into the Gulf of Maine: black sea bass, Maryland blue crab, red hake, turbot, squid, dogfish and others.

As warming oceans contribute to the decline of some cold-water Gulf of Maine species, the warming could be helping lobsters. Lobstermen in the Gulf of Maine are finding females maturing and bearing eggs earlier in life, increasing their reproductive success, Beal said. In the 1980s, egg-bearing lobsters barely measuring a pound were only found farther south in warmer waters, such as in Long Island Sound, according to Beal.

The warming oceans have also done a number on some of the lobster’s traditional predators: groundfish. The cod is one of the lobster’s most common predators early in the crustacean’s life, but cod are increasingly hard to come by in the Gulf of Maine.

Lobstermen have caught lobster in record numbers in the past three years, but where they’re catching them has changed. The lobster catch in Maine’s southern counties hasn’t dropped off in raw numbers, but it hasn’t seen the spike Maine counties up the coast have. In 1997, according to the Maine Department of Marine Resources, the lobster catch in Washington and Hancock counties accounted for 27.4 percent of the Maine’s total lobster catch by weight; York and Cumberland counties’ share was 24.8 percent. In 2014, Hancock and Washington brought in 53.1 percent of the lobster catch while York and Cumberland counties brought in 12.7 percent.

Connecticut and Rhode Island, meanwhile, have watched their lobster fisheries collapse over the past 15 years as the action has shifted to cooler waters up north.

Lobsters are finding hospitable habitat in the Gulf of Maine. Lobsters like to hide out in kelp, and sea urchins like to feed on the algae. And sea urchins were generally plentiful in the Gulf of Maine, and largely unfished, meaning they were eating lots of lobster habitat, Beal said. Then, the urchin fishery took off in the late 1980s, reaching a 41.6 million-pound peak in 1993.

“The sea urchin fishery took off, then it became a boom and bust,” Beal said.

A decade after peaking, the sea urchin fishery fell to 6 million pounds. Today, fishermen take in less than 2 million pounds of urchin. That means lots more kelp for lobsters.

After the lobster, Maine’s second-largest fishery by weight is the lobster’s bait, Atlantic herring. The herring is the most popular type of bait for lobstermen, further highlighting the lobster’s increasing dominance over Maine’s fisheries. (The lobster fishery already accounts for 69 percent of the value brought in by Maine’s fisheries.)

Herring are a critical cog in the lobstering wheel. They don’t just act as bait to entice lobsters into traps. Because of the vast quantity of lobster traps and the hundreds of millions of pounds of herring lobstermen use as bait, herring are also a critical lobster food source.

A 2010 study published in the journal PLOS One found that lobsters with year-round access to herring as bait grew 15 percent faster than lobsters without constant access. The researchers calculated that the herring-induced weight gain added $25 million in value to Maine’s annual lobster landings.

While herring are generally abundant in the Gulf of Maine, they are another species that depends on the gulf’s cold-water habitat. Warming waters, along with the continued potential to be overfished, could put the herring, lobster’s No. 1 bait source, at long-term risk.

The regulation of Maine lobsters is regarded as a success. If the success of Maine’s lobster fishery doesn’t last, it won’t be due to a failure of regulation. Since the mid-1990s, Maine has managed its lobster fishery using co-management — a system that largely formalized many of the conservation-oriented practices lobstermen had employed for decades. In each zone, an elected council of lobstermen can recommend rules — generally, conservation measures — to the commissioner of marine resources. The lobster’s success can, in part, be owed to that responsible, shared management system.