Thirty years ago, when detailed surveys of ocean life began in Long Island Sound, it was unusual for spot fish to find their way into trawling nets.
Today, it's unusual if they aren't present.
Spot fish, with their characteristic black spot just behind their gills, were best known as a species found south of Delaware. No more. Now when the net is emptied, like it was one day last week, spot fish are flapping on the sorting table more often than not.
"We used to hardly ever see spot," said Kurt Gottschall, a marine biologist with the state Department of Energy and Environmental Protection. "Now, they're one of our more common fish. We caught more today then we have in most of the years that we've been out here."
Out with the cold species
The spot and other warm-water species are part of a vanguard that, biologists say, is heralding a profound change in Long Island Sound and one that's being caused by global warming. As the Earth and its oceans get warmer, the Sound follows suit.
The Milford Harbor water temperature has increased about 3 degrees since the 1960s, according to the New England Interstate Water Pollution Control Commission's 2012 report, "Sound Health." Other reporting stations in the Sound have seen similar increases.
Gottschall said scientific surveys from the Chesapeake Bay to the Gulf of Maine all tell the same story -- fish and other marine life are edging farther north to find the water temperatures in which they're best adapted to live.
"The northern kingfish is another species that we're seeing more of today," he said. "Years ago, we'd hardly get any, but today, we saw more than we'd see all year back in the 1980s."
Conversely, cold-water species are seen less frequently, the poster child of this phenomenon being the lobster.
"We used to come up with a lot of lobsters. Today, not a single one," Gottschall said. "The winter flounder is another one of those species that has decreased in abundance in the last several years."
And the numbers of scup, snappers and bluefish are down from where they were two decades ago, biologists say.
"We got about 30 bluefish today," Gottschall said. "Years ago, that number would have been in the hundreds per tow. Maybe it'll pick up later. A little worrisome."
Also of concern was the lack of first-year scup, juvenile fish that should have been plentiful.
The sporting scene notices
Sport fishermen, too, are seeing a shift.
"Just the other day, I saw someone come in with a triggerfish," said Larry Gonzalez, who works at Rudy's Tackle Barn in Greenwich. "You don't see those every day."
The gaily striped triggerfish is usually found in the tropical waters off Florida and Bermuda. Scientists say these tropical species will follow gyres of warm water north as they're pulled along by the Gulf Stream.
"The Gulf Stream will form these warm core rings that will get pinched off and travel north with the stream," Simpson said. "What concerns us more are the mid-Atlantic species. All of these are becoming more abundant. It's apparent they've shifted their distribution northward."
Still, encounters with these tropical gate-crashers are "not the oddities that they once were," according to the DEEP magazine, Connecticut Wildlife.
Long days on the Sound
The work aboard the John Dempsey, DEEP's largest scientific vessel, is more like what you would expect on a commercial fishing trawler.
The net is dropped off the stern, dragged for about 20 minutes on the bottom and then hauled up. A cinch rope is loosened and the startled fish drop onto the sorting table. Then the crew of six or so gets to work tossing the different species into buckets and baskets.
Everything gets a good look, from jellyfish to horseshoe crabs. Smaller, less common species like the amusing pufferfish, are dropped in old plastic cottage cheese and sour cream containers. Hefty animals, like dogfish sharks and skates, wind up in much larger fish baskets.
The catch is kept in water; every effort is made to return them to the Sound alive.
The trawls look at just about everything, and scientists have to fill out more paperwork than a court clerk: Water temperature and salinity. Bottom quality. Geographic coordinates. Type, size and weight. Total catch biomass. Even seaweed is catalogued.
Trawls are often cut short by old lobster pots and other human cast-offs.
"One time, we picked up an aircraft landing gear," said crewman John Stearns. Whatever happened to the rest of that plane is anyone's guess.
Dozens of fish have their ages ascertained, usually by scraping off a few scales and looking at them under a microscope back at the lab. Some fish have scales that have annular rings, just like trees.
With other species, such as bluefish, their craniums are opened with a reciprocating saw to retrieve their otolith bones -- a part of their inner ears that sense sound, motion and orientation. Otolith bones also have annular rings and continue to grow for the life of the animal.
Still other fish are quickly dissected to determine their sex. Occasionally, the stomach is opened to figure out what they're eating. On most days, the John Dempsey is out for up to 12 hours. The ship has to sample most of the Sound during the spring and again in the fall, a tall order for a single boat.
The cataloguing is done as quickly as possible so the fish can be tossed back alive. Those that don't make it become lunch for the gulls and pelicans that shadow the boat for an easy meal.
Sometimes, a sea creature that was tagged in another scientific study is hauled in; these tag numbers are noted in the logbook and tossed back. Sometimes, species needed by other researchers are set aside for them.
The shift in species has had one benefit, especially for sport fishermen -- a few of the new interlopers are very good to eat.
"The sea bass is a really good one," Simpson said. "They really have exploded in the Sound and they're a great eating fish. Fantastic."