LogoDiscardLess Strategies for the gradual elimination of discards in European fisheries

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.
Barry O’ Neill, Dan Watson and Laurence Fauconnet