Reducing Drag in Towed fishing Gears - Fishing Trials to Evaluate the Performance of a trawl Constructed from T90 ('turned mesh') Netting

Summary

This report describes a demonstration trial of a single-rig, demersal whitefish ‘Rockhopper’ trawl constructed entirely of T90 or ‘turned mesh’ netting. This is the first time that T90 technology has been used in this way in the UK. The trawl used for this trial was designed and constructed by Icelandic trawl manufacturer, Fjardanet which has been pioneering this technology for a number of years. Descriptions of the fishing gear used are included. The report describes some background to the development work and the concept of T90 technology. Eight days of commercial fishing trials were carried out in January 2008 using the Shetland based vessel Mizpah operating on local fishing grounds about 50 miles NE of Lerwick. Despite being hampered by poor weather a total of 21 hauls were completed. The aim of the trials was to evaluate the performance of the T90 trawl with reference to fuel savings as a result of the reduced netting drag associated with this technology. This was done by measuring the main gear performance parameters and comparing them with those of the vessel’s existing gear of the same general dimensions. Some catch sampling was undertaken to examine other reported attributes of T90 trawls such improved catch rates, size selection and catch quality. From a gear performance perspective the T90 trawl compared well with the vessel’s own trawl. The information gathered on the fuel efficiency aspects of the gear however did not show any significant benefits from the T90 trawl despite indications that the netting drag had been considerably reduced, (~20%). The findings from the catch data were inconclusive. There were some indications of larger size ranges of some species being caught and retained by the T90 trawl but the findings did not appear to bear out the findings and experiences of the Icelandic fishermen to the same extent. There was more loss of marketable size grades of some species, particularly whiting associated with the T90 trawl. This was thought to be as a result of the more consistent mesh opening noted throughout the T90 trawl. The positive side of this was that there were no discards recorded. There was no noticeable difference in catch quality detected. The results showed that the combination of the T90 trawl fitted with a conventional diamond mesh codend of the same mesh size produced the best commercial results. The results were insufficient to draw any firm conclusions on the overall effectiveness of the T90 trawl and a number of proposals for further work have been highlighted.

Author

• Ken Arkley

Publication Reference No.

SR595

Publication date

01 February 2008