Discards - Unwanted catch

In their nets, fishermen do not only find fish they aim to catch, but also unwanted bycatch: fish that has no economic value, for which they have no fishing rights (quota) or that is too small. When this unwanted bycatch is returned to the sea, we call it discards. In 2013 the EU decided that discarding should no longer be allowed and that all catch that is under the quota system should be landed. Wageningen University & Research is collaborating with the fishing industry on research into the amount of discards and smarter fishing techniques to have less unwanted bycatch.

What are discards?

When fishermen go out to sea, they not only catch the fish they aim for (full-size, commercial ‘target fish’), but also other species of fish, undersized fish and benthos (e.g. crabs and starfish). The untargeted but commercial fish is landed, but the rest is returned to the sea. The latter is commonly known as discards or unwanted catch.

Why throw them back?

There are a number of reasons for discarding. It goes without saying that if a fisherman is allowed to sell his catch and expects to get a good price, he will not throw it back into the sea. In other words, fishermen have to navigate between two determining factors: regulations and the market. The main reasons for discarding are:

  1. The catch is of little or no value. For example: we do not eat starfish; there is only a limited market for dab, which affects the price (supply/ demand), Europeans do not eat jellyfish (unlike the Japanese) – so there is no market for them here;
  2. The catch is damaged;
  3. The catch may not be landed because:

    • The fish are too small (there are legal minimum sizes);
    • The fisherman has reached his quota for that species;
    • There are rules about the catch composition per 24 hours;
    • The fish is a protected species (e.g. sturgeon or certain species of shark)
  4. Fishermen sometimes throw fish of a certain size back because other sizes are more profitable (particularly important if the quota are tight). This practice is known as high-grading and is illegal.

If a fisherman is able to catch only the fish he wants to catch, he will be fishing selectively. Selectivity depends on a number of factors, including fishery technology, fishing methods, size of the mesh, target species, season, weather, fishing area and the fisherman’s own behaviour (choice of fishing area, for example). This means that selectivity within a fishery is variable. The regulations and the market also play a role: some adjustments in the nets that can increase selectivity are not allowed; and sometimes certain adjustments are beneficial to reduce discards, but they have an adverse effect on the share of profitable fish in the catch.

Landing obligation

What is the landing obligation?

In June 2011, the European Commission put forward a proposal to introduce a landing obligation. The main reason for this was that discards were seen as a wasteful practice. In February 2013, the European Parliament and the European Council voted in favour of a landing obligation (discard ban).

In 2015, a landing obligation was introduced in pelagic fisheries (fishing for fish species swimming in schools, such as herring and mackerel). Between 1 January 2016 and 1 January 2019, the landing obligation will be introduced in phases in the demersal (bottom) fishery. However, this landing obligation does not mean that all discards must be landed: the landing obligation only applies to the so-called target species. For the Dutch flatfish fishermen on the North Sea, it regards plaice and sole. All other unwanted bycatch should therefore simply be returned to the sea. Because the landing obligation is introduced in stages, in 2016 for example for North Sea fishermen who fish for sole with the pulse or beam trawl, in principle only the catches of undersized sole between 19 and 24 cm must be landed.

By limiting the discards of quoted commercial species, the EU expects the fishing industry will invest in innovations that make their fishing more selective. The European Union expects that this landing obligation will ultimately lead to a more selective fishery, with less ecological impact, and better fish stocks. The idea behind this is that this translates into a profitable and healthy fishery in the longer term.


The current regulations include a number of exception rules for the landing obligation:

  • Fish subject to a fishing ban: It is forbidden to keep on board and land species that are not allowed to be fished according to European legislation. This concerns for example endangered shark and ray species. These species still have to be thrown overboard as quickly as possible and unharmed.
  • Fish with a high chance of survival: Species that are scientifically proven to have a high chance of survival in a particular fishery do not have to be landed.
  • 9% species flexibility: If the quota of a by-catch species is exceeded, the quantity of quota exceeded (maximum 9%) may be deducted from the quota of the target species. This only applies if the stocks of the by-catch species are within safe biological limits.
  • Fish for which a de minimis exemption applies: In the European discards plans for certain fisheries, it has been proven that it is difficult to achieve greater selectivity, or where disproportionately high costs are involved in the landings of undesirable species caught with a de minimis exemption. All catches under a de minimis exemption may be discarded to a certain maximum, but as soon as the exemption is exhausted, all catches must be retained on board and landed.
  • Fish showing damage caused by predators: incidentally caught fish that have been eaten by e.g. seals, predatory fish or birds must be discarded.

Research into discards and the landing obligation

The EU expects fishers to make much more use of their knowledge of discards and how to avoid them. By fishing differently with existing gear, by developing new fishing techniques and by fishing in other areas or at different times, discards can probably be partially avoided.

Wageningen Marine Research carries out ongoing research into discards on behalf of the Ministry of Economic Affairs. Discards have an effect on fish stocks and the ecosystem. Some stock assessments take the number of discards (plaice, flounder and cod, for example) in account. Thus research of catch compositions of the Dutch fleet is part of Wageningen Marine Research' work. The research is conducted at sea, on board of commercial fishing vessels.

Wageningen Marine Research traditionally collects its data via observers, Wageningen Marine Research' staff joining the crew of a fishing vessel taking samples of the catch and registering species, length and age compositions. In addition to the observers, since 2009 fishers themselves have been taking samples of discards. Every week, 3-5 vessels monitor their catch and supply samples. The samples are processed and analysed by Wageningen Marine Research. This cooperation has provided a better overall picture of the temporal and spatial variation.

In addition, in view of the landing obligation, Wageningen Marine Research (together with Wageningen Economic Research) participates in a number of projects exploring the effects of this obligation in relation to management (setting quota), fishing practices (e.g. processing catches) and research (e.g. monitoring).

Publications about discards - unwanted catch