Latest BIM gear trial on improving energy efficiency demonstrates a 51% increase in catches of haddock by using green LED lights on the headline at nighttime
Dr Ronán Cosgrove, Fisheries Conservation Manager, BIM
The drive towards net zero carbon emissions by 2050 is encouraging development and transition to use of more sustainable fuels and more energy efficient fishing methods. BIM and Irish fishing Industry gear-based research on improving energy efficiency has focused on Nephrops and whitefish trawl fisheries which generally use more fuel than other fisheries.
This works includes development of more hydrodynamic trawls, reduced drag otter doors, and enhanced catch detection using acoustic sensor technology in the Nephrops fishery. In the whitefish fishery, efforts have focused on pairing up on trawl operations to reduce energy use and boost profitability with further pair trials in the commercially important demersal seine-net fishery due to occur shortly.
Artificial lights are another potential method for improving catch and energy efficiency in terms of kg of produce per litre of fuel. Depending on the species and type of light used fish can display negative or positive phototaxis i.e., they move toward or away from the light. Studies have shown attraction of species like snow crab and mantis shrimp, and negative responses from turtles and fish such as smelt and yellow tail, and a bit closer to home, Celtic Sea cod:
BIM previously assessed lights on raised-fishing line trawl gear, a BIM/Irish Industry developed gear measure which successfully mitigates catches of low-quota cod in the Celtic Sea. Results showed a significant 62% reduction in cod but also some reductions in haddock, hake and whiting with fish likely moving away from the light and dipping under the fishing line to escape. Potential negative effects on commercial viability made it difficult to recommend use of lights on the raised fishing line but the study did raise some interesting questions around potential energy efficiency applications.
Led by Martin Oliver with assistance from Matthew McHugh and working in close collaboration with Kevin Granville and crew on board the MFV Virtuous, our latest trial aimed to take advantage of this negative phototaxis to try and improve catch rates of target species and operational efficiency. 14 green Lindgren-Pitmann® light emitting diode (LED) lights were attached at around 150 cm spacing on the headline of a standard trawl targeting fish species off the southwest coast. Catches were compared with a standard trawl with no lights. Haddock was the dominant species corresponding to 90% by weight of all commercial species landed with 60% of haddock catches occurring at nighttime.
Results showed a significant 51% increase in haddock catch weight with lights on the headline during night with no significant effect during daytime. These differences could be caused by the absence of day light penetration potentially linked with differences in haddock depth preferences during nighttime. Greater quantities of larger haddock were retained corresponding to a 64% increase in the value of haddock caught with lights during nighttime.
Whatever the reasons behind these differences, adding green lights to the trawl fishing line is a simple inexpensive option to improve efficiency in this fishery with the lights effectively paying for themselves in around one nightime haul.
Observed hake catches were 28% greater with lights on the headline at nighttime but catches were too low to tell if this is likely to be a consistent result. Further testing by whitefish vessels could help understand the effects of lights on species like haddock, hake and cod in standard and raised-fishing line trawls, and also potentially seine-net or gillnet fisheries.
BIM would like to thank David, Kevin and Jamie Granville and crew of the MFV Virtuous for a successful collaboration. This work was funded by the Irish Government and part-financed by the European Union through the EMFAF Operational Programme 2021 – 2027. Full reports on the lights and all BIM work on improving energy efficiency are available at www.bim.ie/publications/fisheries