Original publication: December 2015
Authors: Thünen Institute of Baltic Sea Fisheries: Christopher ZIMMERMANN, Sarah B. M. KRAAK, Uwe KRUMME, Juan SANTOS, Sven STÖTERA, Lena VON NORDHEIM
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Options of Handling Choke Species in the View of the EU Landing Obligation – The Baltic Plaice Example

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In May 2013, the reformed EU Common Fisheries Policy (CFP) was adopted (European Union 2013). One of the salient features of the new CFP is the Landing Obligation, described in Article 15 of the basic regulation (1380/2013). In a phased approach, extending from 1 January 2015 to 1 January 2019, “all catches of species which are subject to catch limits […] shall be brought and retained on board the fishing vessels, recorded, landed and counted against the quotas […]” (EU 2013, Article 15.1).

Under the Landing Obligation ‘choke species’ may cause problems. The term choke species is not clearly defined; here we use a rather wide definition: “A choke species is a species for which the available quota is exhausted (long) before the quotas are exhausted of (some of) the other species that are caught together in a (mixed) fishery”. There are many examples for potential, perceived or real choke species under a landing obligation, and different ways to solve the problems arising from the bycatch of those for various fisheries. The Baltic Sea is the EU region where the landing obligation will be introduced first, along with fisheries on pelagic species in all EU waters. Plaice (Pleuronectes platessa) serves as the example for a potential choke species in the Baltic Sea. Plaice is a quota species and discards regularly occur because some countries catch more than covered by their national quota while other countries lack a quota at all. The original intention of the introduction of a landing obligation in EU waters – to incentivise changes in fishing practices towards higher selectivity – appears to be at risk since Article 15 of the Basic Regulation (EU 2013) allows for several flexibilities of utilising quotas and a number of exemptions to the landing obligation. If widely applied, those rules may allow fisheries to continue with their present practices also under a formal landing obligation – which seems to be in clear conflict with the original objective of the approach.


The aim of our study is to determine to what extent plaice could actually act as a choke species in Baltic Sea fisheries, and then provide a framework for guidance how to mitigate any such choke species problems. This framework should give priority to the original objectives of the landing obligation, where a change in fisher’s behaviour was an important expected outcome.


The report is structured in three major sections: In the first we describe stock structure, distribution and stock status for plaice, management areas and total allowable catches (TACs) as well as the international fisheries in the Baltic Sea. Baltic plaice is also distributed in the Kattegat (SD21), therefore this area is included in the analysis. We find that for plaice in the Kattegat, Denmark, Sweden, and Germany are unlikely to experience choke-species problems because the quotas will probably cover the catches with little necessity to change fishing patterns. For plaice in the Baltic Sea (SD 22-32), international catches of plaice have exceeded the TACs in the recent past. Several member states’ fisheries will likely be choked by the availability of plaice quotas, either because they are not sufficient (Germany, Sweden, Poland) or because they have no plaice quotas at all (Finland, Estonia, Latvia, and Lithuania). The affected fisheries are the cod-directed fisheries and mixed flatfish fisheries. The choke species problem might be alleviated if the current trend of a positive development of the plaice stocks and TACs and an unfavourable development of cod stocks and TACs continues. Adult plaice abundance is highest in the northwest (Kattegat and in the northern part of SD 22) and decreases towards the east. The distribution and aggregation of plaice corresponds with areas of high catches, landings, and fishing intensity in the commercial fisheries.

In the second chapter we have a closer look at two national fisheries: (i) The German fishing fleet as an example for the Western Baltic Sea with relatively high catches of plaice and limiting quotas; and (ii) the Latvian fishing fleet as an example for the Eastern Baltic Sea with few plaice bycatches but no quota to land plaice.

The major part of the German plaice landings (and catches) is taken by demersal trawls in a mixed flatfish fishery and in a cod-directed fishery in the Belt Sea (SD 22) in the first and fourth quarter of the year. Some catches of plaice are also taken in the remaining  quarters and in the Kattegat (SD 21), Arkona Sea (24) and Bornholm Sea (25), and rarely further to the east. The German discarding of plaice varies not only between areas and quarters, but even between trips and hauls of a single vessel. In the western Baltic the discard proportions are lower than in the eastern Baltic (with exceptions). In SD 25 and SD 26, major parts of the catch are regularly discarded, although the amounts are quite small. The estimated total annual catch of the German fleet is between 200 – 300% of the recent (landings) quota for plaice. With the implementation of the Landing Obligation, this would cause problems if no international quota swaps would take place and if fishing practice would continue as before. A disproportionally high share of the overall German plaice landings stem from a targeted fishery conducted by a few vessels operating from harbours in Kiel Bight (western SD 22). These vessels already acquire additional plaice quota from swaps with Denmark, Sweden, and Poland.

Latvia has a demersal fishery that takes place all year in SD 25 and SD 26 (trawlers and gillnetters) and targets cod and flounder. In SD 28, the passive fleet segment fishes all year; additionally, a small trawling fishery takes place in the second, third, and fourth quarter. Just a few gillnetters also fish in SD 24 in the western Baltic. The amount of Latvian plaice bycatch in sampled trips is highly variable, ranging between 12 t and just a few kg. But even these small amounts would cause a problem after the implementation of the landing obligation, because Latvia has zero plaice quota.

In chapter 3 we develop the guidance framework through a decision tree outlining the possibilities to mitigate choke-species problems.  The tree provides guidance on the sequence of application of the solutions, which seems pivotal to ensure the objectives of the introduction of a landing obligation are met.

Choke-species problems can be mitigated by (i) a national redistribution of quotas or by (ii) international quota swaps, especially if the overall availability of TACs is sufficient as seems to be the case with plaice in the Baltic.

Among the changes in fishing practices in the original spirit of the landing obligation are (i) the use of gear with an improved selectivity and (ii) spatio-temporal avoidance of unwanted bycatch. We provide two different technical approaches to reduce unwanted flatfish bycatch in roundfish fisheries which have recently been developed by the Thünen Institute of Baltic Sea Fisheries. There are also solutions available to reduce roundfish catches in flatfish directed fisheries. Recent experimental sea trials carried out in the Baltic Sea have given promising results, and a reduction of unwanted plaice catches by ¾ seems feasible with this gear. Spatio-temporal avoidance depends on (fisher’s) knowledge of species’ abundance at medium and small scales. We document some success stories from around the world where fishers share such knowledge and avoid unwanted bycatch. As a first step, the catch composition of the German fishery (relevant target species relative to plaice in time and space) is explored. The patterns in catch composition present some scope for avoidance of plaice while maintaining good catches of the target species (cod, flounder and dab). However, the spatio-temporal scale of the data that are available to us (ICES statistical rectangles and quarters of the year) is considered too crude to develop a practical solution; fishers usually have information on a much finer scale and thus the shifting of fishing effort to areas with lesser plaice abundance might have even more potential.

The provisions allowing for exemptions and flexibility, recently the solution preferred by most regional management bodies and the fishery to avoid a choking of fisheries under the Landing Obligation, were explored for their potential to solve the choke species problem and meet the objectives of the CFP. The two provisions for flexibility, the inter-annual flexibility (quota can be banked or borrowed from or to the next near) and the inter-species flexibility (up to 9% of the bycatch could be counted against the target-species  quota provided the by-caught stock is within safe biological levels) have limited use to solve the problem. For Baltic plaice, the latter rule would be useful for those fisheries with zero plaice quota, but the eastern stock in SD 24-32 is considered data limited and thus not within safe biological limits, so the provision is not applicable for those countries that would profit mostly, i.e. Estonia, Latvia and Lithuania. From the two exemptions, one is at present generally not applicable in the Baltic (the de minimis-rule where up to 5% of the catch could be discarded and not counted against the quota), while the second (discarding can be continued if there is scientific evidence for high survival of the discarded species) could in principle apply. However, the available studies on discard survival of plaice show that there is high variability in survival both between and within studies and that most studies suffer from severe methodological and statistical shortcomings. Therefore, an exemption for plaice owing to high discard survival would lack any authoritative scientific basis. For all of these provisions, managers should consider that exploitation needs to be within the boundaries of MSY objectives and the precautionary approach, and thus total catches (landings and discards allowed under exemptions or flexibilities) are constrained by the scientifically advised amount (STECF 2014). Overquota catches therefore will have consequences on next year’s TACs.

We conclude that the problem of choke species can be effectively solved and the objectives of the CFP reform met if a structured approach is applied, in the Baltic Sea and likely also elsewhere. All potential solutions to the choke species problem will have economic consequences, primarily for the fisher, but also for the retailer, consumer and the society at large. The analysis of these consequences was beyond the scope of the present study but will be addressed in larger Horizon2020 projects within the next few years. The aim of this study was to analyse the significance of choke species in the Baltic Sea, using the example of plaice, to provide ideas how to mitigate apparent problems, and to analyse the impacts of those measures. Most of the analysis and solutions described  here can be performed or applied for other stocks or regions. Our recommendation is indeed to apply the principles in line with the decision tree before deciding on a regional discard mitigation strategy.

Link to the full study: http://bit.ly/563-399

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