Wednesday, August 21, 2013

Selectivity of Modified Groundcables to Reduce Sea-bed Impact Tested

Many projects funded in the spring of 2013 are now underway, and some have already completed their field work and are now in the analysis stage.

In June, Neal Pike on the F/V Sandi Lynn and David Goethel on the F/V Ellen Diane tested a modified groundcable setup designed to reduce sea-bed impact.  They collected data over five days of fishing that included six sets of tows with the two vessels fishing side-by-side.

The FV Ellen Diane (in picture) and the FV Sandi Lynn (in the distance) tested the modified groundcables in June.
The results will be of interest to both managers, who may consider opening previously closed areas to gear with a reduced environmental footprint, and to fishermen, who are interested in whether fishing with such gear would make sense from a business standpoint.

During the experiment, one vessel used a modified ground cable with 8” rockhopper disks designed to keep the ground cable off the bottom while the other used its standard ground cable.

David Goethel points to the 8" rockhopper disks used to keep his bottom cable raised above the seabed

“We were interested in seeing two things from this experiment,” explained Goethel.  “First, we wanted to see if a ground cable like this one actually stayed off the bottom and, second, we wanted to see how this would affect the fish we catch.”

Although the data still were being analyzed in August, the fishermen already had a few impressions about how the gear performed.

“We definitely seemed to be getting fewer flounder with the ground cable with the disks,” Goethel said.  “I would not use the modified cables when fishing for flounders, but they could be used though when fishing for cod, haddock, and pollock during hard-bottom fishing when bottom contact is not desired.”

He added that the modified cables probably could be used anywhere the principal founder catch is blackback such as areas of George’s Bank where blackbacks are pursued with bottom gear.
The video supported Goethel's conclusion that the ground cable modification reduced impact on the bottom.

“The video was a bit grainy," said GMRI technician Croy Carlin.  "But, you could definitely see that the cable is off the bottom.”

   Video courtesy of Croy Carlin - Gulf of Maine Research Institute

A more rigorous analysis of the catch and fuel consumption results will be available on the GEARNET website this fall.  The results will be posted alongside a related GEARNET project that tested a low-impact semi-pelagic or "LISP" trawl offshore aboard vessels operated by Jim Odlin’s Atlantic Trawlers Fishing Inc. in July.

Those tests looked at the impact of a system that includes semi-pelagic doors and 8” diameter cluster disks, which also are hypothesized to reduce bottom-impact while maintaining a profitable catch.

Stay tuned for more updates from projects on the water!

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