New prawn trawl will reduce by-catch Published: 23 April, 2007
A NEW type of trawl developed by the research and marketing support group Seafish, will reduce the by-catch of whitefish and give a better quality prawn catch as well.
The prawn sector has come under sustained pressure from conservation groups and EC officials who claim that prawn boats also have a significant by-catch of pressure stocks such as cod and haddock.
Seafish began developing the trawl over three years ago. The ‘coverless trawl’ uses a series of design features at the mouth of the trawl to discourage fish entering the net. Part of the top panel of netting has been removed giving fish the opportunity when pushed upwards by the ground-rope to escape over the headline of the trawl. Previous technical measures focused on providing fish with escape panels once they were caught in the net.
A new Seafish study has been carried out to assess the quality of the prawns caught in the coverless trawl, by comparing them with the catch from standard trawls. This was carried out on a typical single rig prawn trawler operating out of the north east of England. The trials were conducted using the ‘matched pair’ technique, whereby each trawl was towed under commercial conditions once per day for a total of eight consecutive days.
The results showed that prawns caught in the coverless trawl suffered from significantly less damage than those caught in the standard commercial trawl, with 12% more undamaged prawns and 18% less highly damaged animals in the catch. The coverless trawl caught 10% more prawns than the standard trawl and reduced discards by 56%. It caught 26% less commercial cod, haddock and flatfish than the standard trawl, and 66% less commercial whiting.
Duncan MacInnes, secretary of the Western Isles Fishermens Association, said this should allay any concerns about the effects prawn trawlers had on other species. The trawl doesnt open so much and isnt as heavy so it doesnt catch so much fish. Fishermen have been under a lot of pressure recently to reduce by-catch. They have tried escape panels, but there was no indication of how much damage even the escaped fish had suffered. This is better because it allows the fish to escape without going into the trawl at all. The trawl itself fits well with the way quotas have been going, with a reduction in whitefish and an increase in prawns. This is exactly what the new trawl does. The industry is trying its best to develop new techniques and gear to fish sustainably. The buyers and supermarkets are now looking for sustainable methods as well and this new trawl should fit these aims very well, said Mr MacInnes.
The higher proportion of undamaged prawns means that more of the catch could also be suitable for the lucrative live trade for prawns. Over the course of the trials, the coverless trawl produced higher earnings with the increase in the prawn catch. The improved prawn quality more than compensated for the reduced fish catch. Other benefits included reduced damage to gear, reduced catch sorting times, easier handling and the potential for lowered fuel costs, because the coverless trawl can be towed with smaller trawl doors.
Mr MacInnes said the new trawl should make prawn fishing, which is extremely important on the west coast, more profitable. He said: The price of fuel has increased considerably over the past two years, but this trawl is lighter and doesnt need so much fuel to tow it. It also produces a better quality prawn that isnt damaged, so more can go for the whole prawn market rather than the prawn tails market. This means fishermen will get around £3,000 a tonne more for prawns than when they sold them as tails.
Marcus Jacklin, Seafish fisheries technologist, said: “This work has established that the coverless trawl causes less damage than a conventional trawl and improves the quality of the prawn catch. As well as enabling fishing boats to gain financially through higher prices for a better product, the resultant reduction in discards enables prawn fishermen to operate in an environmentally friendly manner.”
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