A University of Maine survey of 11 Gulf of Maine locations indicates that young lobsters have declined by more than half of their 2007 levels — significant since lobsters typically take about eight years to reach the legal harvesting size.
The downward trend has lobstermen, retailers, state officials, and ocean scientists concerned that the impact could soon be felt on dinner tables nationwide. Maine lobsters were 85 percent of the nation's lobster catch in 2012.
Warmer ocean temperatures, pollution, atmospheric conditions and changes in predation and availability of food could all be to blame, say scientists, state officials and industry leaders. Lobsters are very sensitive to even subtle changes in temperature, scientists say.
Maine Department of Marine Resources officials say the decline does not appear to be the product of overfishing as some environmental groups contend.
The last three years have brought record hauls to Maine's lobster industry, more than 350 million pounds — by far the most for any three-year period according to state data that go back to 1880. The value of the catch has topped $1 billion for the first time.
Larger catches generally follow high levels years earlier of baby lobster settlement — the process in which young lobsters reach the ocean floor and grow. The boom in lobster catches in recent years follows a trend of heavy lobster settlement in the mid-2000s, university scientists say.
But that pace might not be sustainable, says Carl Wilson, the state's lobster biologist.
"It's our first indicator that things might be changing in the future," Wilson said. "Low settlement, it's thought, in the future will lead to lower landings."
Maine lobsters' eggs hatch in the early summer and larvae swim freely about six to eight weeks before settling at the ocean bottom as inch-long post-larvae. Divers for the University of Maine have been tracking their settlement rates since the late 1980s.
The American Lobster Settlement Index tracks 13 settlement areas, 11 of which are in the Gulf of Maine, two in Canada and three in Massachusetts. All show decline, scientists said.
Scientists also track young lobsters farther away, off Rhode Island and Buzzards Bay, Mass., but saw slight upticks in numbers there last year.
The first-year lobsters could be thinning out for a variety of reasons, said Rick Wahle, the settlement index's founder and a marine ecologist with the university. One possibility is rising ocean temperature, as the Gulf of Maine's temperature began rising more quickly in 2004, he said. Gulf of Maine surface temperatures have increased by an average of .026 degrees Celsius each year since 1982, but after 2004, the pace of warming increased to .26 C per year, according to a 2013 report by the Oceanography Society.
Some of the most lobster-rich areas have seen a dramatic decline, including midcoast Maine, which dropped from about two-and-half first-year lobsters per square meter in 2011 to just above zero in 2013, data shows. Midcoast Maine's settlement level was close to two baby lobsters per square meter in 2004 and 2005 and about one in 2006, the years in which lobsters now being caught were likely settling. The temperature at the bottom of the Gulf of Maine rose from just above 7 C to about 8.5 C in that time.
The higher temperatures could cause lobsters to migrate north, a trend also suggested by higher settlements being seen in the southern Gulf of St. Lawrence in Canada, Wahle said. The temperature change could also increase predation from fish following the warm waters north, he said.
Fewer baby lobsters are unlikely to directly translate into a drop in lobster catch, as market forces and laws governing lobster catch limits also play a role, Wahle said. But the university's data suggest a dropoff in landings could come in 2016, possibly earlier, he said. The findings come as some scientists and fishermen are concerned that Maine's lobster industry bubble could burst after years of record catches.
"It's telling a story of gradually — and more recently rapidly — declining settlement in the Gulf of Maine on a widespread basis," Wahle said. "This is what's raising lots of concern."
Maine has approximately 4,500 active lobstermen and about 2 million lobster traps in the water, Wilson said. Retailers are monitoring the downward trend among baby lobster settlement, said Pete McAleney, a past president of the Maine Import Export Lobster Dealer's Association. He acknowledged the cyclical nature of settlement and catch.
"It makes sense that it's going to happen after a while, because the catch has been sky high," McAleney said.