The director of MIT Sea Grant's Center for Fisheries Engineering Research wants to build a better dredge-even though he's the first to admit that current dredges do a fine job of catching the creatures.
What current dredges don't do, says Goudey, is take into consideration unintended consequences, such as damaging bottom habitat -- a concern since the 1986 reauthorization of the Magnuson- Stevens Act introduced the issue of essential fish habitat.
The standard dredge used to harvest scallops consists of a heavy steel towing frame and a chain bag that drags along the sea floor behind the frame. The dredge includes a cutting bar, which has little effect on a perfectly level bottom. However, on a more typical sea bottom with sand waves or humps and valleys, the cutting bar levels the bottom so that the chain bag can scoop up scallops in its path.
But along with the scallops, says Goudey, other organisms living on and buried just below the surface can get caught or damaged.
Is there a way to catch scallops without leveling the bottom in front of the dredge?
Goudey figured that would require disturbing or lifting the scallops, in preparation for the chain bag, without physically contacting the ground. The best option for that, he decided, was to use jets of water. So Goudey experimented with devices of different shapes and sizes to see how they affected scallop shells placed on the bottom of MIT's towing tank. The most promising results were implemented in a prototype dredge.
“We built a small dredge fitted with four 11-inch hollow hemispheres positioned close to the seabed and mounted on pivots so that if they hit something they could deflect up out of the way,” says Goudey. The hemispheres “produce a downward directed jet of water that seems to have a profound effect on scallops when they're hit by it,” he explains. Goudey notes that most mobile creatures near the dredge can escape from its path. “While a conventional dredge impacts subsurface organisms, this one does not,” he said.
“Essentially the scallops...start spinning up in the water high enough so that they're still suspended in the water when the chain bag comes by.”
In field tests on Stellwagen Bank off the Massachusetts coastline, the newfangled scallop dredge caught 50- to 60 percent of a normal catch. “We believe that with a little adjusting...that catch rate could become competitive,” says Goudey.
A talk Goudey gave prompted an invitation from the University of Wales in Ireland to try the dredge out off the Isle of Man. So in April, Goudey shipped the dredge across the Atlantic, then followed along for field tests.
In those trials, the researchers used the dredge aboard a research vessel and a commercial scallop trawler, both with the participation of local fishermen. The dredge was particularly successful in catching queen scallops. A lower than expected catch of larger types of scallops suggested that some simple modifications may make the dredge more effective. Additionally, the dredge caused far less damage to scallops than conventional gear. As a result, Ireland may employ a version of the gear as part of a developing management strategy for scallop fisheries.
Written by Andrea Cohen, MIT Sea Grant
Elizabeth A. Thomson | MIT News Office
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
20.02.2018 | Life Sciences
20.02.2018 | Medical Engineering
20.02.2018 | Physics and Astronomy