A new study experimenting with the square mesh panel design in prawn (Nephrops) trawls could have important conservation benefits for some key whitefish stocks.
Recent sea trials have been carried out on the Buckie-registered prawn trawler Heather Sprig by researchers from the Sea Fish Industry Authority (Seafish). They found that by using low diameter knotless netting in the square mesh panel there was a significant reduction in the unwanted bycatch of juvenile haddock and whiting without affecting catches of the main target species of prawns, cod and flatfish.
Haddock showed the biggest fall with a 52 % reduction in the amount of juvenile fish caught. For whiting, there was a 16 % fall.
The study, which was funded by the Scottish Executive Fishing Industry Partnership, was comparing this new type of netting with traditional and much heavier, double twine knotted material. The high tenacity of hi-tec Dyneema material used in the trial netting means that a reduction in twine diameter does not impact upon the overall strength of the trawl, yet it increases the escape area for juvenile fish.
Seafish Technology Director John Tumilty welcomed the findings:
"We're continually looking at ways in which we can refine gear designs to help fishermen target their efforts in the most efficient way and at the same time assisting conservation management by reducing discards. This project still has some way to go and the twine used in the trial is not widely available yet. The initial results are promising and we will continue to work with fishermen to come up with more effective solutions."
Other benefits of the new type of twine include high resistance to abrasion and the ability to maintain the correct configuration of the square mesh panel, but as well as not being widely available, it is currently much more expensive than standard netting.
According to Seafish gear technologist, Ken Arkley, the study does pave the way for fishermen to look for compromise solutions based on the premise that the finer the twine, the greater the selectivity benefits.
"There is still scope for improvement by considering gear options and specifications between the two ends of the spectrum examined in this work. The aim is to achieve consistent mesh shape and stability with the lowest practical twine diameter," he says.
