BOSTON – The best picture scientists can snap of the condition of important New England fish stocks can be blurry, considering the fish they’re trying to count live in the dark.

But now Sen. John Kerry is asking the head of the National Oceanic and Atmospheric Administration to find out if a developing sonar technology can bring new clarity.

In a letter to Jane Lubchenco last month, Kerry asked her to designate $1 million for a system that can scan dozens of square miles of ocean in an instant.

A fish stock’s health is the critical factor when regulators decide how much fishermen can catch. A bad estimate can mean an unnecessarily low catch limit, and that can end a fishing business, or cause unintended overfishing.

A developer of the Ocean Acoustic Waveguide Remote Sensing (OAWRS) system says it can open up an underwater view comparable to a full-screen movie, as opposed to the tiny “pixels” of the underwater picture that researchers glimpse today with periodic trawls of the ocean bottom.

“It is crucial we determine the full capabilities of this method,” Kerry wrote.

NOAA scientists see promise in the technology for spotting certain species, but say it has significant “blind spots.”

“To me, it’s just another tool in the toolbox,” said NOAA scientist Russell Brown.

Sonar fish finders have been used by fishermen for years. Those devices are like a single flashlight pointed downward, revealing only the spot of ocean the vessel is over, said Massachusetts Institute of Technology researcher Nick Makris, one of OAWRS’ principal developers.

The OAWRS system uses lower frequency sound waves to detect objects farther away. Those waves are transmitted in all directions from a string of loudspeakers that hang below one ship and reflect off different objects.

These “echoes” are picked up by a line of underwater microphones towed behind a second ship, instantaneously providing readings from an area hundreds of kilometers across.

That dwarfs the area today’s research trawlers cover.

Trawlers help create a picture of fish stocks in a different way. Their catch becomes an important part of formulas used to estimate fish populations and set catch limits.

Rulemakers usually set catch limits a few years into the future, basing them on projections of what stocks will look like. But the estimates become more uncertain the further ahead regulators look. If a species ends up healthier or weaker than regulators predicted, its catch limit could be based on outdated data.

For instance, regulators in the mid-2000s said they had overestimated the stock of yellowtail flounder by 77 percent, and were forced to introduce tough, protective restrictions. In 2010, regulators raised the pollock catch limit by nearly six times, after new science showed it was a healthier stock than previously thought.

And now there are rumblings that Gulf of Maine cod, which scientists recently reported was getting healthier, could actually be struggling badly.

“You can’t ask people to live with policies that impact their paychecks and livelihood based on data that’s outdated,” Kerry said.

Fisherman John Haviland of Marshfield said he’d welcome any upgraded data, but he’s not confident it would mean improvements in the wrongheaded fishery policies that he said shut him out of the groundfish fishery this year.

“I may be jaded,” Haviland said. “Especially when you’re one of the fishermen that fell through the cracks.”

The OAWRS system is based on the sonar technology used during the Cold War for jobs such as detecting submarines, Makris said. His team adapted it so it could be used as an imaging system, to “see what we could see in the ocean,” he said.

They learned the system could spot fish in 2003, when Makris was on a research vessel off Long Island and scientists detected an object the size of Manhattan that was gradually changing shape. It turned out to be a massive shoal of herring.

Makris said the “swim bladders” on fish help sonar identify them.

The air-filled bladders help fish regulate their buoyancy between depths, and range in size depending on the fish. The OAWRS sound waves bounce off different-sized bladders in distinctive ways, so researchers can narrow down what species they’re seeing.

Researchers can then apply what they know about certain fish — such as where they swim at certain times, or how they behave — to determine the species.

Some regulated species, such as dogfish, don’t have swim bladders. Behavioral cues would be crucial to identifying such fish, but it’s unknown if the OAWRS system could reliably see such fish. “We haven’t tested it,” Makris said.

NOAA’s Brown says OAWRS technology appears limited because it has a blind spot: it doesn’t reach into the areas closest to the sea floor, where so many commercially valuable groundfish species dwell.

“In trying to get an overall picture for our fishery’s management needs, yes, it is a significant blind spot,” he said.

Makris said with the $1 million Kerry is requesting, scientists could find out if OAWRS can get the same good information about various groundfish as it got for herring. Such data would still need extensive verification to be used in stock assessments.

In her response to Kerry’s request, Lubchenco wrote that OAWRS has “the potential to eventually improve marine resource assessments” and could be eligible for a competitive grant program. That’s a long way from “yes.”

In the meantime, Makris said scientists are developing the technology for other uses.

 

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