Can you find three skates in this seafloor photomosaic? The images were taken by a newly developed camera system called HabCam, which also can automatically count and measure scallops. (Mosaic by Richard Taylor, courtesy Scott Gallager, WHOI)
HabCam (short for “habitat mapping camera system”) is hoisted aboard the scallop boat Kathy Marie for a test run. (Tom Kleindinst, Woods Hole Oceanographic Institution)
Related Links
» More Photos of What's Down There HabCam's official illustrated project page, with oodles of photos, including HabCam in action and strange denizens of the New England seafloor.
Part of the fun of fishing is never knowing exactly what might be
swimming around beneath you. But that mystery is a major annoyance when
it comes to keeping track of fish populations.
Now, a new undersea camera is bringing light to the pitch-black depths
of New England’s scallop beds. Called HabCam (short for “habitat
mapping camera system”), the device was developed by scientists at
Woods Hole Oceanographic Institution (WHOI) working with Cape Cod
scallop fishermen. Fishery managers hope to use the invention to take
sharp images of the seafloor and then automatically count and measure
scallops on the bottom.
Contrast that with the current technique for monitoring scallop stocks:
For 30 days each summer, a research vessel blindly drags an 8-foot-wide
dredge across 500 miles (800 kilometers) of ocean bottom, one mile at a
time. After shoveling through the catch, measuring the scallops, and
estimating how many the dredge left behind, biologists such as Dvora
Hart of the National Marine Fisheries Service (NMFS) decide on the
year’s allowable catch.
The exhausting sampling program works. It’s one reason the U.S.
Atlantic scallop fishery has become one of the biggest fisheries in the
world and one of a few whose stocks are expanding. Last year’s catch
was worth about $400 million, five times the 1998 catch, Hart said. Draining the water out of the photos
HabCam improves on dredging by adding a 21st-century efficiency: It
brings back photos of the seafloor instead of pieces of it. WHOI
scientist Scott Gallager and colleagues built a high-resolution camera
and four very bright strobe lights—all housed in a 10-foot-long cage of
bright-yellow welded pipe. Festooned on every corner with cushions of
tire rubber, it’s rugged but hardly streamlined.
“It looks like the roll cage on a double-A fuel dragster,” said Richard
Taylor, a retired commercial scallop fisherman and one of Gallager’s
collaborators.
A commercial scallop boat, the F/V Kathy Marie,
tows the device at about 10 feet (3 meters) above the seafloor,
traveling at 3 to 5 knots. Onboard, scientists and fishermen can watch
the seafloor go by, 230 feet (70 meters) or more below, as a
fiber-optic cable brings camera images back onboard.
Now, instead of shoveling through dredge piles on deck, the HabCam team
has to make sense of more than 300,000 images—up to 1,000 gigabytes of
data—per day. The individual photos, four to five of them taken per
second, must be pieced together into continuous strips, or
photomosaics. Then the strips have to be corrected for the way light
behaves under water.
At first, even under the flash of the four strobes, images are murky
and the colors are washed out. So Norman Vine spends much of his time
on image processing.
“I’m trying to pull the plug and drain all the water out of the
picture,” he said. Vine is a retired commercial fisherman, lifelong
computer hacker, and son of Allyn Vine, the WHOI engineer for whom the
deep-diving sub Alvin was named.
When Vine is finished, the images are crisp and bright, as if they were
taken from a glass-bottomed boat on a sunny day. Next, a computerized
process called segmentation automatically extracts outlines of fish and
shellfish from the jumbled background of sand, rock, and seaweed.
A range of advantages
Gallager’s group collaborates with researchers at Los Alamos National
Laboratory who are developing new ways to segment complicated images.
“They consider seafloor images to be a real challenge,” Gallager said.
After segmentation, another program classifies the extracted targets
into real categories such as scallop, flounder, starfish, and sea
grass. That program uses advanced pattern recognition software
developed with help from WHOI biometrician Sanjay Tiwari.
HabCam won’t replace dredging altogether, Hart said, because
biologists still need to make some actual measurements. But HabCam is
easy to use, day or night. It provides 100 percent visual coverage and
fine spatial detail (compared with dredges, which miss many scallops
and bring up a mile's worth of catch all at once). HabCam offers real-time images,
too, allowing surveyors to double back on interesting areas.
HabCam promises a major advance in scallop monitoring, helping fishery
managers judge when they should close or reopen precise portions of the
ocean. Next year, when NMFS’ new research ship Henry B. Bigelow goes
into service, Hart plans to put HabCam through its paces while making
simultaneous dredge runs for comparison. Meanwhile, the Alaska
Department of Fish and Game is building a replica of HabCam from
Gallager’s specifications to assess its scallop fishery.
Development of HabCam was funded by
the scallop industry’s Scallop Research Set-Aside Program. At the end
of each scallop season, proceeds from a few final days of fishing are
deposited in an account used to fund research. NOAA NMFS supports
continuing work on image classification. Test runs using the F/V Kathy Marie were
courtesy of owner Arnie DeMello and Capt. Paul Rosonina. Other
collaborators include WHOI staff Jonathan Howland, Andrew Girard, Lane
Abrams, and Hanu Singh; Cape Cod fisherman Ron Smolowitz; and NMFS
biologist Paul Rago.
If you think U.S. Census Bureau officials have their hands full
locating and counting everyone who lives in the United States, consider
the men and women at the National Oceanic and Atmospheric
Administration’s National Marine Fisheries Service who are charged with
counting fish in U.S. waters.
Their mission is to prevent the
decline of fish stocks and the loss of habitats that fish and shellfish
need to breed, spawn, feed, or grow. But a whole lot of water gets in
the way of their ability to locate those essential habitats and to
estimate fish stocks.
In recent years, scientists at Woods
Hole Oceanographic Institution have been lending a hand, applying new
technologies and methods to see into the sea and help assess and
maintain fisheries.
