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Report on the effect of light lines on fish behaviour, and on the light line and circle hook experiments

Report Highlights

  • Proto type light-emitting devices for use on trawl fishing gears have been developed and tested
  • Laboratory experiments investigating the behavioural response of haddock and cod to light of different wavelengths, intensity and strobing rates.
  • Continuous lines of light have been shown to influence the height at which some species enter a trawl gear
  • Illuminated grids in the extension section can be used to direct fish out of the trawl gear or to different codends where further selection can take place.
  • Fishing trials of circle hooks vs J-hooks were held in the deep-water longline fisheries in the Azores.
  • Catch of deep-water sharks was higher using circle hooks than J-hooks, without significant improvement in terms of hooking position or fish condition.

The methods/approaches followed

  • Design and development of physical hardware, software and user interfaces.
  • Laboratory experiments with captive fish.
  • Catch comparison fishing trials.
  • Fishing trials with circle and J-hooks alternated.

How these results can be used and by who?

  • Fishers and net makers – to develop gears that utilise light to select for fish that best match their quota allocation.
  • Fishing gear scientists – to better understand how light can be harnessed to improve trawl gear selectivity.

Policy recommendations

  • This report demonstrates the potential of using light to improve the selective performance of gears, which if to be fully exploited requires (i) committed research support and (ii) a regulatory framework that is sufficiently flexible to accept readily new technologies and novel gears.
  • The circle hook trials demonstrate that the J-hooks already used in the commercial longline fishery in the Azores are the most suitable hook type for the mitigation of deep-water shark bycatch.
Authors:
Barry O’ Neill, Dan Watson and Laurence Fauconnet

Deliverable:
3.4
Pages:
22
Year:
2018