Report Open Access

"Challenge" experiments in a compiled cluster report and final avoidance manual

Reid, David

Ulrich, Clara
Calderwood, Julia; Moore, Sara-Jane; Hehir, Imelda; Graham, Norman; Mortensen , Lars; Olesen, Hans Jakob; Ulrich, Clara; Feekings, Jordan; Krag, Ludvig; Malta, Tiago Veiga; O'Neill, Barry; Balazuc , A.; Goffier, E.; Soulet, E.; Rochet, M.J.; Leleu, K.

Executive Summary

This Deliverable is principally intended to provide the results of the three “Challenge” trials carried out under Task 4.2 the Fisherman’s story – “challenge” experiments. As the “challenges” included both tactical/strategic adaptations to the LO and also allowed free use of gear changes or modifications, we have combined the two aspects in this report.

Chapters 1-3 present the results of the “Challenge trials” in Ireland, Denmark and France, and their findings. Chapter 4 summarises the material in Deliverable 3.1. and a component on developing industry-science collaborations on improving selectivity from Deliverable 3.2. 

In the “challenge” experiments individual vessels and crew were challenged to reduce their discards by whatever legal means available. Each vessel could fish alternately with their normal approach and with the aim to minimise the discards over a predetermined period, reporting the decisions they make and the rationale behind them. Observers were placed on-board to collect catch and discard data, and also train crews in self sampling approaches. Skippers were asked to set themselves a target for discard reduction between the trial and the control trips, and this was the core of the “challenge”. The targets could be in terms of reducing discards of TAC species in general, or of those that represent the major “choke” species in their fishery. Catch data were analysed to determine success at reaching this target, and successful tactics included in the “best practice” manuals and disseminated at annual case workshops.

Challenge trials were carried out in three different countries and across a number of fisheries:

•          Ireland – one demersal trawl vessel targeting whitefish (cod, haddock and whiting) and one targeting nephrops with additional catches of the same fish species.

•          Denmark – 12 vessels mainly fishing cod and saithe, with three nephrops targeting vessels. The vessels towed a mix of single and twin rigs, and were distributed between the North Sea, the Skagerrak, and the Baltic Sea.

•          France – 3 vessels targeting a mix of species including cod, whiting, squid cuttlefish and some pelagic species. The vessels were all trawlers, two under 18m, and one over 18m.  

The approach was slightly different in the three countries. In Denmark, the main option explored by fishers was gear modification, and the data were mostly collected by the fishers themselves, supplemented with Fully Documented Fishery (FDF) methods. In France and Ireland, the approaches included both gear and tactical modifications, with full observer coverage.

  This deliverable also includes the outputs from Deliverable 3.1. on gear based methods for reducing discards. Particularly important for the „challenge trials“ was the „Selectivity in Trawl Fishing Gears“ report, which also included a range of fact sheets on the performance of particular gears and modifications. This manual is available for download at and also on

Gear based changes used in the „Challenge trials“

Changes to the gear figured strongly in fisher‘s choices in all three trials, with the aim of improving selectivity and reducing unwanted catches. This was the main thrust of the Danish study. Here the fishers chose a range of different approaches

•          Seven of the vessels used some form of changed mesh size in the cod end of the net. Usually this involved larger mesh size, but in the Baltic vessels they also trialled reduced mesh sizes

•          Three vessels inserted escape panels into the net

•          Two vessels trialled separator panels with two cod ends

•          One vessel used a topless trawl and one used a modified mesh in the Bacoma panel

In the French trials a number of gear changes were tested.

•          The inclusion of a larger mesh cylinder in the extension

•          Separator panels with two cod ends

•          Increased mesh size in the cod end and extension, and T90 mesh

One of the Irish vessels (the nephrops targeting vessel) decided to use gear changes, and opted for a quad rig nephrops net, with large mesh square mesh panels in all four extensions.

The outcomes of these trials were somewhat mixed. In the Danish trials, nine vessels were able to reduce the discard ratio in the test fisheries (three in the North Sea, three in Skagerrak and three in the Baltic Sea), while two vessels (from the North Sea) actually increased their discard ratio and one North Sea vessel showed no difference in discard ratio.  The improvements ranged from less than 2% for four of the vessels, 2-7% for four others, and, in one case, a 17.6% improvement. In the French trials, there was insufficient time after making the gear changes to reliably check their performance. However, the vessel using the mesh cylinder (CMC) approach reported little loss of commercial catch, and in some cases reductions in discard volume. The separator panel with two cod ends could not be evaluated, but the skipper was still very positive and felt it had value. In general, the fishers did not feel that the changes in cod end meshes achieved the results they had hoped for small fish, and there were concomitant losses in commercial sized fish. Finally, in the Irish trials the use of the SMP in the quad rig allowed the vessel to keep fishing significantly longer before choking on the cod that were the main choke during the control phase of the study.

In conclusion, the use of modified gears to improve selectivity, and reduce the scale of discarding showed considerable promise during the “Challenge trials”. In all three cases, the use of added panels, changes in cod end mesh size and configuration, modifications to the extension, and the use of separator panels with twin cod ends showed some improvements. It should be noted that these improvements were often quite small, and would probably not solve all the problems fishers would face under a full implementation of the LO. Additionally, these were the fishers own trials, and could not always be full substantiated in a scientific context.

What was clear though, was that fishers had many, potentially valuable, ideas on how to improve their gears in the context of the Landing Obligation. One, very positive approach that could be taken, would be to identify an approach that was able to test and “fast track” such initiatives into routine use. In the last part of Chapter 5, we provide a proposal for a framework for industry-led initiatives on gear development in the context of the Landing Obligation that could assist in this context.

Tactical and Strategic changes used in the „Challenge trials“.

Behavioural changes were principally tested in the Irish and French “Challenge trials”. In the Irish trials, the whitefish targeting vessel aimed to use changes in both the time of day and also in the depths at which he fished. The vessel also tried to use movement between management areas to maximise his time fishing for the month. The main issue for this vessel in the control period was a very early choke on cod and haddock in all management areas. The combination of area changes, and behavioural changes allowed a small change in choke time across all areas from 10 to 12 days. There was some evidence that the skipper was actually trying to avoid discards during the control periods as well. He had somewhat higher discards in the months prior to the trials than in the control month during the trials. This may have impacted on the outcomes from the changes he made. The Nephrops vessel, while focused on the gear changes outlined above also used movement between management areas to reduce the choke problem.

The French vessels behavioural changes were mainly focused on the potential for avoiding “sensitive” areas, characterised by high catch rates of quota species under MCRS. The outcomes suggested that the large vessel already did this in its normal practice, and that scope to do any more was limited. For the smaller vessels, their main operating area with high discards was within the three mile zone along the Channel coast, where almost 70% of their catch was usually discarded. Avoiding this area would clearly help with their LO mitigation. The key issue was that, while discards are high in this zone, it is also their main area of operation. These are small, artisanal vessels, and this area is both close to their home ports and also sheltered from bad weather. As a consequence, the skippers were reluctant to avoid this area during the trials. However, it remains a potential valuable tool for LO mitigation, and means to encourage the avoidance of this area should be explored.


In conclusion, the “challenge trials” showed that there was some scope for the use of both more selective gear, and changes in behaviour, both locally, and in moving between management units, to reduce discards, and mitigate the impacts of the LO on fishing viability. Fishers in all the trials did believe that these changes could make some difference, even if they did not work as well as expected in the limited context of the Challenges. It should be noted though, that even when the trials were able to reduce discarding or the impact of “choke”, the improvements were generally quite small. So, while such changes may help fishers comply with the LO, and reduce discards, it is still not sufficient to avoid significant impacts on their economic viability. Notwithstanding this, we consider it desirable to continue working with fishers on both gear and behavioural based responses to the challenges implicit in the LO. The trials were all successful in terms of the level of collaboration, and in some of the outcomes, and means should definitely be actively sought to continue this type of work.

Highlights: • Based on the "challenge" trials there is scope for fishermen to reduce their catches of unwanted fish both in terms of under Minimum Conservation Reference Size quota species, and "choke species" fish; • The "challenges" allowed fishermen to develop their own solutions or approaches to the problems raised by the Landing Obligation; • They were able to utilise both gear based approaches (mesh sizes, escape panels and other modifications), and tactical changes (e.g. change of location, fishing deeper, or moving between areas, or changing the time of day of fishing). • Many of the gear modifications were detailed in the DiscardLess Avoidance Manual – Deliverable 3.1; • Most of the "challenge" trials showed that the improvements in selectivity, either through gear or behavioural changes, were generally small, and would not alone prevent unwanted catches under the LO; • The time scale of the "challenge" trials did not all allow the fishermen to make all the changes they might have wished, both gear and behavioural, but many expressed a desire to continue using, and developing, these methods in the future; • There were clear indications that all solutions were local in their application. All the fishermen in the "challenges" used different methods of gear or behaviour, which were adapted to the particular fisheries in which they worked. No single approach can then be expected to provide a global solution.
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