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Commercial Fisheries News
Volume 37 Number 1
September 2009
NMFS scallop survey enhanced by HabCam high-rez digital photos
WOODS HOLE, MA – The Northeast Fisheries Science Center’s annual scallop dredge survey, which wrapped up on July 3, was further enhanced this year by high-resolution digital photos taken in collaboration with the Woods Hole Oceanographic Institution using the Habitat Mapping Camera System, commonly referred to as HabCam.
The HabCam is a towed underwater camera used to ground-truth dredge catches and scrutinize bottom habitat. It also was used in 2007 and 2008, but this year, for the first time, it was towed on the same boat conducting the dredge survey.
According to Dvora Hart, chief sea scallop assessment scientist for the science center, the survey covered bottom in both open and closed areas and in Canadian waters in cooperation with Canadian scientists.
“We found very high numbers of seed scallops in the Great South Channel and on the northern edge of Georges Bank,” she reported. “This is very encouraging news as our observed numbers were even higher than last year.”
However, recruitment in the Mid-Atlantic Bight from Virginia to Long Island was the weakest in 12 years, she noted, although biomass overall in the Mid-Atlantic remained high. These results largely mirrored those obtained through the SMAST video survey.
The science center’s survey documented biomass increases in both the Delmarva and Hudson Canyon areas but reported a drop in the Elephant Trunk Area.
“This decline is not surprising since over 40 million pounds of scallop meats worth over a quarter billion dollars have been landed from the Elephant Trunk Area since it reopened in 2007,” said Hart.
Sea squirt invasion
With the help of the HabCam, survey crews documented high densities of an invasive sea squirt, a tunicate of the genus Didemnum, on the northern edge of Georges Bank.
The tunicate, which the HabCam caught on camera for the third year in a row, was first reported in 2003. It’s of particular concern to scientists because it smothers many bottom-dwelling organisms, and its acidic “skin” can prevent seed scallops from settling on the ocean floor.
“We saw it in patches in only one area we surveyed, but it is a real concern,” said Hart.
She also noted that survey crews were surprised to find large numbers of small ocean quahogs on Georges.
“We had over 10,000 per tow in several locations, which I have never seen in my 10 years doing the survey,” she said. “We usually see just a few.”
The survey was conducted aboard the 146' Hugh Sharp, a research vessel operated by the University of Delaware that also conducted last year’s scallop survey. The science center has been conducting annual scallop surveys since 1979. /cfn/
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