Shrimp Size Sorting Success!

Text, photos, and videos by Rachel Gallant
Northeast Consortium Fisheries Specialist

April 4, 2006

My alarm went off at 3:15 am this past Tuesday, and I awoke grateful for the extra hour of sleep. The night prior, Captain Vincent Balzano, called to tell me that we'd leave the dock an hour later than planned, given that I'd be driving up from Portsmouth to Portland to meet his boat to go out for a day of research. What a nice guy!

It was a clear, crisp morning with just a sliver of color on the horizon over the islands of Casco Bay. I climbed down the ladder at the wharf onto the F/V North Star, greeted with a big smile from Balzano's crew member, known only as "George." With Balzano at the helm, four of us set out through the islands towards the growing color of the sky line, including George, research technician Ben Foster, and myself. Today's mission: to continue tests of a system of grids and escape vents in shrimp fishing gear that sort out and release juvenile shrimp from the catch, in addition to minimizing the harvest of non-target species.

So far, the gear being tested has shown real promise. It's an unusual dual grid system, which has a shrimp size sorting grid in front of a Nordmore Grid. Nordmore Grids are designed to lead large fish out of the net through escape vents while shrimp and small fish go through the grid and into the codend. Such grids have been required in the North Atlantic shrimp fishery for several years now, minimizing bycatch significantly. Catching juvenile shrimp and small fish is still a problem, however, but project leader Pingguo He of the University of New Hampshire, and others involved in this research, think they have found a solution.

A few years ago, He and Balzano teamed up to test whether increasing the number and size of escape vents in front of a Nordmore Grid would lower bycatch while not compromising the amount of shrimp that was caught. They were funded by a FY2004 project development grant from the Northeast Consortium for a small project that would test this theory. The net proved successful, and the research team came back to the Northeast Consortium the following year with a larger proposal and a few more project partners, including fisherman Tim Eddy and gear scientist Dan Schick of the Maine Department of Marine Resources. They wanted to combine the use of the Nordmore Grid and increased escape vents with inserting a shrimp size sorting grid in front of the Nordmore Grid and escape vent for small shrimp.

The idea behind the size sorting grid really began during a trip in December 2003 to Newfoundland 's fishing gear flume tank at Memorial University by Schick, Balzano, and fishermen Proctor Wells. Fishermen had tried using a size sorting grid in the past, placing it behind the Nordmore grid, but found it to be cumbersome and to lower the total shrimp catch significantly. While testing a model of shrimp gear at the flume tank for an entirely different project (testing if kites in the codend can minimize catch of juvenile shrimp, funded by the Northeast Consortium in 2003), the research team met a gear designer who had been working on flexible plastic grids. Together, they created a shrimp sorting grid that would be much more manageable for fishermen to handle and would allow only small shrimp to escape readily.

So in November of 2005, Balzano and He went back to the tank with their model of the dual grid system in hand, as a step of the larger, FY2005 cooperative research project. After some minor adjustments, the gear was ready to go to sea.

The day I joined the project, the research team was testing the dual grid system. We did three tows of the test net, followed by one tow with a regular commercial net, that included a Nordmore grid. After each one-hour tow the shrimp and bycatch were sorted and weighed (I helped between snapping photos). Length measurements were taken of the bycatch and a sub-sample of the shrimp was reserved for Foster to measure back at a Gulf of Maine Research Institute lab that the project is borrowing. Each tow produced about four boxes of marketable shrimp, which we brought back to the dock to sell under the Northeast Consortium's general policy that 75% of the proceeds return to the Northeast Consortium for future cooperative research funding.

Field work had begun just a few weeks prior, with tests on Balzano's boat of just the Nordmore grid with increased escape vents, the finfish reduction system, followed by comparative tows with Eddy and his F/V Persistence. Soon to follow the current tests of the dual grid system, will be more comparative tests with Eddy.

It was a productive day out there. Balzano, He, and all the project participants are pretty happy with how the net is performing so far. I could really see that the dual grid system was catching a lot fewer juvenile shrimp and was surprised that the total shrimp catch was about the same as for the standard net.

Even though this project is only part-way through, fishermen have already been asking Balzano where they can get a sorting grid. Since the gear is so novel in this region, local distributors aren't carrying it yet, but Balzano has been helping fishermen get the grid directly from the Canadian designer. As Balzano he put it, "Customs is kind of a pain, but I do it, because I like the product and want to help guys get it." This is one of the great benefits of cooperative research, when fishermen and scientists put their heads together to come up with solutions that the industry wants to get a hold of.

Videos (click picture to play):

	Vincent Balzano explains the day's plan while changing the experimental net to the standard commercial net. (12 MB)
	This video shows the catch made with the standard commercial net. (7 MB)
	Setting the control net out. (19 MB)
	Hauling back the control net. (17 MB)