URI researchers are finding wild fluctuations amid an overall warming trend, with consequences for the Bay's ecosystem.

ABOARD THE CAP'N BERT — A harbor seal pokes its mottled head out of the water, soulful eyes visible above a bristly mustache, before diving back down to snatch fish from the net being winched aboard the trawler.

"Gettin' a free meal," Captain Tom Puckett remarks with a shake of his head.

As the otter trawl net is hoisted up on the A-frame across the boat's stern, it's clear that it's nowhere close to full. But it doesn't matter. The Cap'n Bert is not a commercial fishing trawler. It's a research vessel owned and operated by the University of Rhode Island's Graduate School of Oceanography.

The 53-foot stern trawler is out on Narragansett Bay on this winter day carrying out its weekly ritual of testing the water temperature and other indicators and taking samples of marine life.

Doctoral student Joe Langan pulls open the net, spilling fish and shellfish unceremoniously onto the deck. He sorts the catch, just as he has done every week since September and as others have done before him, stretching back more than five decades as part of one of the oldest continuous marine research projects in the world.

From the wet and writhing pile, he picks out sea robin and skate, silver hake and red hake, rock crabs, spider crabs and lobsters — all species that are normally found in the Bay this time of year.

But when Langan gets to the bottom, he carefully picks up a flat, light-brown fish and pauses to study it.

"A Gulf Stream flounder," he finally says. "Which should not be here."

The little flounder is a warm-water species that shows up in May but would usually be gone by the time the temperature drops in December.

It is of course only one fish, but its presence here in the waters off Whale Rock on this January morning is yet another sign that Narragansett Bay is changing.

"And we're seeing it happen," Langan says.

Higher highs, lower lows

Marine life in the Bay is gradually shifting toward warm-water species, with a reduction in bottom-dwellers and an increase in invertebrates. The long-term effects on the ecosystem are unknown.

One of the major drivers of the changes — if not the main one — is a steady increase in the Bay's temperatures.

Surface waters in the mid-Bay increased between 2.5 and 2.9 degrees Fahrenheit between 1960 and 2012, according to the most recent published study on the subject, which was based on data from the URI survey and also relied on readings from a National Oceanic and Atmospheric Administration monitoring station. Warming in the winter months over that half-century was even higher, with an increase of between 2.9 and 3.6 degrees, according to the study by a team led by Boston University professor Robinson W. Fulweiler.

The warming trend has continued over the last three years, but 2015 was unlike any other, with the Bay experiencing temperature fluctuations that were the most extreme in the 56-year history of the survey.

Temperatures in the Bay last February sank to 30 degrees, the lowest ever recorded by the survey. The low temperatures persisted through March before warming more rapidly than normal in the spring.

By August, they neared the record highs set during the "Northwest Atlantic Ocean heat wave" of 2012 that was caused by an unusual trapping of warm air in the jet stream. After tapering off in the fall, the Bay this past December hovered around 50 degrees, setting a record high for the month.

"What stands out is that you can have extremes in weather even as the overall trend is warming," says Jeremy Collie, a URI professor of oceanography who has been in charge of the survey since 1998. "We really can get these swings."

And that is consistent with predictions from climate scientists who say that the Earth isn't just warming in a linear fashion but is also experiencing disruptions to historical weather patterns that can lead to extreme events.

The warm December, Collie acknowledges, was due in part to a powerful El Niño, a periodic event characterized by warmer-than-normal waters in the Pacific Ocean that influence global weather patterns by transferring more heat to the atmosphere.

But the overall warming of the Bay is occurring hand-in-hand with a long-term increase in air temperatures. Fifteen of the Earth's 16 warmest years on record have occurred since 2000, according to the National Oceanic and Atmospheric Administration. Last year was by far the hottest ever recorded.

The Bay is, in a sense, a bellwether when it comes to the effects of warming waters because of its location at the junction of what ocean scientists call the Boreal Province — cold waters that include the Gulf of Maine to the north — and the Virginian Province — warmer waters of the mid-Atlantic to the south. A small change in temperature can have a big effect on the Bay's marine life.

A study led by Collie that analyzed population trends for 25 common fish and shellfish in the Bay since 1959 found only a handful of species whose numbers have held steady. Cold-water species, such as winter flounder, cunner, longhorn sculpin and lobster, have dwindled while warm-water fish, such as scup, long-finned squid and butterfish, have thrived.

"There are losers and winners," Collie says. "You can think of the Boreal species as losers and the Virginian ones as winners."

Weights and measures

The Cap'n Bert steams out of the Wickford Shipyard on Jan. 25, the Monday after the weekend storm that dumped several inches of snow on Rhode Island. The temperature hovers in the 30s. It's colder than early January, when air temperatures crested at 50 degrees for a spell, but it's nowhere close to last winter, when parts of Narragansett Bay iced up and the Cap'n Bert froze to the dock.

There's a mild chop on the water and not a single cloud overhead as Puckett steers into the Bay. The boat will conduct two trawls: one in the heart of the Bay, near Fox Island off North Kingstown, and a second at the mouth of the Bay, near Whale Rock off Narragansett.

Langan drops a probe into the water to measure depth, salinity, temperature and dissolved oxygen. The surface temperature reading comes back at 36 degrees — just above the long-term average for January.

"Nice and cold," Langan says.

As the trawl starts, Puckett cruises at a painfully slow two knots. Through trial and error, researchers have found that the net trailing behind the boat spreads out to its full 60-foot width at that speed, sweeping along the maximum possible area of the floor of the Bay. In 30 minutes, the boat travels one nautical mile.

As winches whirr and the net is retrieved, Langan warns that there probably won't be much in it.

Marine life in Narragansett Bay follows a pattern through the year, says Puckett, a retired commercial fisherman who has captained this boat since 1991. There are few fish around in the winter, but as the months pass and the water warms, the food chain rebuilds. Seaweed grows and feeds scup. Squid mature and are eaten by fluke. The small fish become prey for striped bass and bluefish.

Langan's job is to sort the catch by species, separating them into baskets and weighing each basket to calculate the total mass for each species. For winter flounder, he must also measure their length and determine their sex.

His work is easy after the first trawl. The net holds a handful of Atlantic herring and nothing more.

"Not much to write home about," Puckett says as the Cap'n Bert chugs south to Whale Rock.

'Out of whack'

In his lab at URI's Coastal Institute in Narragansett, which overlooks the Bay, Collie keeps notes from every trawl stretching back to the first one in January 1959. He flips through a binder showing yellowed pages of handwritten notes from early years.

"It's valuable, because we can go back to these records to check the data," he says. "And we do."

He opens a cabinet that holds jars of unusual species that have been caught in the net over the years: filefish, scad, cornetfish — many of them species carried north by the Gulf Stream.

Collie unscrews the lid of one container and uses forceps to lift out a lizardfish, a species with a distinctive reptilian head that is native to tropical and subtropical waters. The fish showed up in the Bay one recent summer in large numbers, sparking concerns that it would displace native species. That didn't pan out. Similarly, a 2010 spike in the population of blue crabs, which are generally associated with the Chesapeake Bay, wasn't permanent.

The changes caused by the higher average temperature are more nuanced, Collie says.

"It alters when species come and go, when they reproduce, when they're younger in the water, the balance between predators and prey," he says. "It upsets the seasonal timing of populations."

Scott Olszewski, who oversees seasonal and monthly trawl surveys done by the Rhode Island Department of Environmental Management, points to the growing numbers of black sea bass, a warm-water fish, in and around the Bay as an example of how the balance is changing. The fish preys on lobsters, which only exacerbates a decline that has seen the annual catch of the crustacean in southern New England drop from 22 million pounds in 1997 to 3.3 million in 2013.

"It's not that we haven't seen them in the past, but the abundance of these predators is increasing," says Olszewski, a supervising biologist of marine fisheries. "We are seeing an apparent shift in species."

Newport lobsterman Denny Ingram is experiencing the rise of black sea bass firsthand. He describes the fish as a voracious eater of lobsters and crabs.

"Thirty years ago, if we saw three or four a day, that was a lot. Now, I'll see three or four in every trap I handle," he says. "Everything is a little out of whack."

It's not just lobsters being affected by climate change. A NOAA study released last week assessed 82 marine species in the Northeast for vulnerability to warming waters, acidification and other effects of climate change. It found that half were very highly or highly vulnerable. Species most under threat include alewife and blueback herring, tautog and winter flounder — all fish found in the Bay.

"Climate change has been impacting fisheries resources in the past 40 years, and it's going to impact resources in the foreseeable future," says Jon Hare, an oceanographer at NOAA's Narragansett lab and the lead author of the study. "If we cannot address these challenges, it is likely we will not be successful in our fisheries management goals."

The Bay's native species aren't going away altogether yet, but their populations are dropping, says Collie. Winter flounder, for example, have plummeted from peaks in the 1970s and early 80s, but so far they are continuing to return to their spawning grounds in the Bay and connected estuaries. As the water warms, though, fewer fish are surviving, he says.

"It's not like they're going to completely disappear within our lifetime," Collie says. "It's just that the population will be severely reduced."

Unsettling changes

As cormorants dry their wings on the stone remnants of Whale Rock Lighthouse in the distance, Langan finishes sorting the catch from the second trawl.

His final tally includes 45 little skate, 2 lobsters and a winter flounder.

Also in the catch is a butterfish and 48 menhaden. Neither species, Langan observes, is normally found in the Bay in January.

Back in Collie's office, when asked in particular about the school of menhaden and what it suggests about Narragansett Bay, he is unequivocal in his answer.

"That's a fairly clear signal of change," he says.

Postscript: Despite the cooler weather during the Jan. 25 trawl, the average for the month was the third-highest of any January recorded by the survey, behind only 2007, a year affected by another El Niño event, and 2012, the year of the ocean heat wave. When the Cap'n Bert went out on Feb. 1, it recorded a surface temperature at Fox Island that was nearly 5 degrees higher than the long-term February average.

— akuffner@providencejournal.com

(401) 277-7457

On Twitter: @KuffnerAlex