New survey finds juvenile scallops abundant

29 Aug 2012
A scallop dredge catch from the Great South Channel. Credit: NEFSC/NOAA

A scallop dredge catch from the Great South Channel. Credit: NEFSC/NOAA

NOAA researchers using a new instrument have confirmed that there are high numbers of young sea scallops off of Delaware Bay.

Unofficially dubbed the ‘Seahorse’ because of its curved and spiny profile, the instrument is the latest and most sophisticated version of a survey system developed at the Woods Hole Oceanographic Institution (WHOI) and used on sea scallop resource surveys conducted by NOAA's Northeast Fisheries Science Center (NEFSC).

This is the first year that the sea scallop survey has used both a dredge and the Seahorse's multisensory, integrated, benthic ecosystem sampling capability concurrently.

"The Seahorse results from nearly a decade of commitment to research and development by the fishing industry, our academic partners, NMFS, and other specialists working toward a mutual goal using a variety of funding sources," said Bill Karp, science and research director at the NEFSC.

The Seahorse is equipped with stereo cameras and strobes (to take colour images), a CTD (to measure conductivity, temperature and depth), fluorometer (to measure chlorophyll), spectrometer (to measure water colour and trace chemicals in the water), dissolved oxygen sensors, and a high resolution side scan imaging system, among other instruments.

"We are excited about this new system because it gives us a way to make a significant leap forward in understanding scallop biology, ecosystem effects, and how well resource management is working," said Deborah Hart, a mathematical biologist at the NEFSC's Woods Hole Laboratory who also leads the agency's sea scallop stock assessment effort.

Towed behind a ship at around six knots (about seven miles per hour) and flying about two meters (roughly six feet) above the sea floor, the Seahorse provides a view of the ocean floor more detailed than any obtained to date by the NEFSC's resource surveys. Initially the Seahorse is only being used for surveying sea scallop abundance and distribution, but investigations of other species, benthic habitat, and ecosystems studies are among other potential uses of the technology.

This year's NEFSC sea scallop survey of the Mid-Atlantic area and Georges Bank was conducted aboard the 146-foot Research Vessel Hugh R. Sharp and the survey found lots of juvenile ‘seed’ scallops in portions of the Mid-Atlantic. Especially high numbers of seed were seen in the ‘Elephant Trunk’ area off of Delaware Bay.

According to Ms Hart, the 2012 observations appear similar to those from 2002, when the largest numbers of juvenile scallops were recorded, which bodes well for the future.

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