Trawling For Clues About The Health Of The Sound

May 31, 2009 at 4:22 pm Leave a comment

Fish surveys create data used by researchers, policymakers 

Aboard the R/V John Dempsey – Captain Rodney Randall turned at the wheel to size up the first catch of this sunny May morning, hauled on board about an hour into what would be nearly a 12-hour workday on Long Island Sound.

State fisheries biologist Deb Pacileo had been shifting levers on the motorized winch to reel in the cone-shaped trawl net. Seasonal research assistants Dan Lee and Mike Trainor, encased in orange bib overalls and raincoats, rubber gloves, steel-toed boots and hard hats, manned the bow to grab yard after yard of net back onto the reel. A few seconds after the ghost of the sinewy mesh bag became visible just below the surface, the two swung it on board. Only its tip was full.

Lee and Trainor untied the net end to empty the contents onto a work table. In a blink, Pacileo, her colleague Kurt Gottschall, and another assistant, Tim Flanagan, joined them and, falling into the well-rehearsed choreography of cataloguing the catch, started sorting skate from squid, scup from butterfish. The captain looked on.

”I hope we get better fish than that today,” Randall said of the paltry haul from dragging the net across a 1.5-mile swath of sandy bottom near Fenwick Point and the mouth of the Connecticut River. “That’s looking pretty slim.”

To the satisfaction of Randall and the crew of the 50-foot research vessel, each of the four successive trawls that day would be better than the last. By the time the John Dempsey’s bow line was fastened to the dock at the state DEP Marine Headquarters in Old Lyme, the team had sorted, weighed, measured, recorded and thrown back well over 1,000 indicators of the condition of the estuary.

Among them were five varieties of herring, four kinds of flounder, two types of dogfish and two of sea robin, a few pinky-sized cod, a striped bass that flipped itself out of the holding bucket onto the deck and a lobster with a death grip on two butterfish, one in each claw.

Each specimen serves like a dot of color on a pointillist painting, contributing to an overall picture of the Sound habitat.

From this day’s work of five trawls, in mud, sand and in-between “transitional” locations randomly selected from a 500-section grid map of the Sound, the team would collect less than 5 percent of the data for this year’s project.

Changes in species populations tracked

The trawl survey, in its 26th year, samples 40 locations in the Sound over five months. Each site is sampled five times – once each in April, May, June, September and October. The resulting data is used by academic researchers, fisheries policymakers and others.

”There’s a lot of species in Long Island Sound that most recreational fishermen don’t even know are there, like fourspot flounder and mantis shrimp,” said Gottschall, seated on an overturned bucket as he recorded the vessel’s position on a computer map. “We see them daily.”
Later in the trip, he held one of these little known but relatively common species, the windowpane flounder, up to the bright mid-morning sun.

”You can see through them,” he said, pointing out the outline of the flounder’s internal organs visible through its speckled scales.

”It’s a terrific program, providing a great data set on the amounts and types of fish and changes in populations,” said Mark Tedesco, director of the federal Environmental Protection Agency’s Long Island Sound Office.

His is one of several governmental offices that rely on the state Department of Environmental Protection trawl survey data to gauge the condition of the Sound and assess any regulation changes that might be indicated. Funding comes from a combination of DEP budget funds, grants and federal motor boat fuel taxes.

The survey, Tedesco said, is unique both in its longevity – having 26 years’ worth of data is extremely valuable in detecting trends – and its breadth. The trawls cover sites from the mouth of the Thames River in Groton to Greenwich Harbor, in both New York and Connecticut waters. This survey is the only source of such comprehensive baseline data on the Sound, Tedesco said, and many scientists depend on it.

One example of its value, he said, is in linking water conditions with animals. At each trawl site, the crew collects a water sample and measures the salinity, temperature, oxygen content and other characteristics.

”They’ve been able to show clearly that when the levels of dissolved oxygen were down, the fish numbers decreased across species,” Tedesco said. “That was enormously useful to us to understanding the benefits of improving dissolved oxygen levels in the Sound.”

That led to regulations and grant programs designed to reduce nitrogen levels from sewage outflows and other pollution sources, which in turn caused the depleted oxygen levels. Tedesco said the trawls gave scientists direct evidence of the relationship of oxygen levels to habitat.

The trawl data, he added, has also contributed to understanding how rising water temperatures in the Sound from climate change are altering the mix of fish species. Over time, the data has shown declines in cold water-loving species such as winter flounder, and increases in those that prefer warmer temperatures, such as summer flounder.

”This survey helps us understand how Long Island Sound is responding to larger forces,” Tedesco said.

Teri Frady, spokeswoman for the New England office of the National Oceanic and Atmospheric Administration’s Fisheries Service, said the data is also used in combination with trawl surveys done by other states and by NOAA throughout the North Atlantic.

”The data are really most influential over time, to give you an idea of the changes,” she said.

Long-term increases and decreases in average sizes and numbers of particular species, she said, are essential to determining what actions are needed to rebuild fish stock, for example, to assess commercial fishing pressures and whether regulations are working, need to be stricter, or can be relaxed.

The Connecticut survey, she said, provides one of the most important data sets for the North Atlantic region, because it samples more sites more times over a longer time span than comparable surveys.

”Connecticut has one of the largest, and it’s pretty comprehensive,” she said.

Lobster decline documented

The co-leaders of the trawl have been doing the survey work long enough – Pacileo for nine years and Gottschall for twice that – to see some trends developing. In Gottschall’s first year, nearly 800 tautog, or blackfish – popular with recreational anglers – came up in the trawls.

”Now we barely get 200,” said Pacileo.

For tautog and a few other species, the survey gauges not only weight, length and numbers, but also the ages of the fish. The biologists extract the cheekbone of the tautog and view it back at the lab under a microscope to count growth rings, like the rings on a tree. For other species, the crew extracts the inner ear bones or takes scale scrapings to find growth rings.

Pacileo’s first year coincided with a peak in the lobster population, just before the hard crash that started the following year and has accelerated. From the trawls that day two weeks ago, the crew counted, measured and weighed only two dozen or so lobsters. Several bore the telltale mottled shells from the disease that has contributed to the sharp decline of lobsters in the Sound.

”Winter flounder has also declined since I started,” she said as the vessel chugged to the second site. “We used to have tows in the spring where we’d fill that whole work table with winter flounder.”

The winter flounder catch for the 2007-08 trawl was 4,550 fish, compared to 10,288 in 1999. For the past several years, the most abundant species collected in the trawls have been scup, also called porgy, and butterfish, and this day’s catch continued the trend. The fourth of the five trawls that day alone netted 764 butterfish, a bluish fish averaging 6 to 9 inches, and 480 scup, which are silvery with blue flecks and typically about 14 inches long.

Most of the catch is thrown back, except for a few dozen squid the crew packs on ice to donate to high school and college dissection classes, and the larger flounder and tautog whose ages will be calculated in the lab. Almost none of the smaller fish survive, but the most of the larger ones, like the striped bass and dogfish, do, Pacileo said.

”We try to get the bigger fish off the table first,” she said, as the crew began scrubbing the measuring table and buckets after the final and heaviest trawl. “They have the best chance of surviving.”
 
By Judy Benson     
 The Day

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