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Discarding of aquatic organisms is a global problem in the world's fisheries, where more than 7 million tonnes are caught and subsequently discarded each year. The understanding of what drives discarding can help provide mitigation measures in the future. Altering management measures which result in high discard rates/ratios may prove beneficial not only to the economic viability of the fishery but also to the biological functioning of the ecosystem. The present Ph.D. thesis, titled "Discarding Discards: Identification of influential factors and possible mitigation tools in demersal trawl fisheries", investigates discarding practices in demersal trawl fisheries and identifies possibilities for reducing discards. In focus, the factors that determine discards, including environmental factors, fishing methods, management regulations, and biological factors have been analysed. This includes an examination of the efficiency of technical regulations currently in force and retrospective analyses of the efficiency of such measures in the past. The thesis consists of a review and 4 papers. Paper I is an investigation of the factors that can potentially influence the discarding of commercial species in the Kattegat. Previous studies that have investigated the factors that influence discarding have typically focused on the discarded portion as a whole, without considering that discards above and below minimum landing size (MLS) occur for different reasons. The study documented that the factors influential to discarding were different for the two subgroups (under and over MLS) and also for the different species. Paper II focuses on discarding in the Baltic Sea cod (Gadus morhua) trawl fishery. Over the past 15 years extensive work has been conducted to improve the selectivity of the gears and subsequently reduce discards. This study investigated: i) the effects that technical measures, namely gear selectivity and minimum landing size (MLS), had on discards and; ii) a wide range of factors that can influence discards and may blur a potential effect of improved selectivity. The results showed that when gear regulations are implemented correctly they are an effective management measure. However, their effectiveness is influenced by a diverse range of factors that if unaccounted for may distort a potential effect of improved/hampered selectivity. Paper III compiles discard data from 11370 fishing events collected across seven European Union (EU) Member States for the North Sea over the period 2003-2010. Knowledge about the spatio-temporal nature of discards is imperative to researchers and regulators but is often lacking. Here we analysed the spatial and temporal distribution of cod discards throughout the entire North Sea together with the main driving factors behind its occurrence. We discuss how such information can be used to improve future fishing activities and their subsequent catch compositions under a discard ban. Paper IV describes the discarding of plaice (Pleuronectes platessa) in the North Sea. Plaice play an important role in the North Sea benthic ecosystem, being one of the most abundant flatfish species and one of the most important species for the fishery. Nevertheless, the plaice fishery in the North Sea is characterised by a high discard ratio, where approximately 50% (by weight) of plaice are discarded. Here we describe the general patterns in these data with particular focus on factors that could be important for management strategies in the future

Discards are defined as the part of the catch that is brought on deck only to be returned to the sea. This Deliverable is the result of an extensive litterature review on the state of knowledge regarding the biological, ecological and technical aspects of the discard issue. Additionally, factsheets have been collated for the various DiscardLess case studies regarding the more specific knowledge available for the various regions. The main findings are summarized as follows: Discarding occurs for a number of reasons including low or no commercial values, undersized fish, or the absence of quota. Discards are driven by a variety of factors (sociological, technical, legislative, environmental and biological) which form a complex network of often interwoven causes and effects, and are highly species, fisheries, and areas specific. However, the root cause is the lack of selectivity of fishing gears or operations, notably in trawl fisheries. Methods for reducing discards are often fishery, fleet, or area specific. They can be grouped into two categories: - Improvements to gear selectivity. For trawls, most of the selection happens in the codend, and modifying mesh size and/or shape is the simplest and most commonly used measure to improve size selection. Additional techniques aiming at sorting the catch in the codend according to morphology include selective grids and square mesh panels (or escape windows). Alterations of other parts of the trawls are also explored, as are the use of deterrent such as physical, acoustic, and electronic modifications. In the case of multi-species fisheries, the range of minimum landing sizes (implemented to protect smaller immature individuals) cannot be all harmonised with the selectivity of fishing gears. Short-term economic losses due to reduced marketable catch are identified as the main reason discouraging the uptake of more selective gears. - Temporal and spatial closures. The main objectives are to avoid areas of high juvenile abundance or high by-catch species abundance. While ...

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.ocecoaman.2019.05.009. ; In the reformed technical measures regulation, the European Union proposed a greater involvement of the fishing industry in the different managerial aspects of fisheries. However, having the industry as a main actor in gear development presents a new suite of challenges. The industry, while addressing an issue in the fishery, can modify several aspects of a fishing gear simultaneously, without considering that some of those changes might have opposing effects. Here we present a case study where a codend, with several modifications, was developed by the industry for the Baltic cod trawl demersal fishery. Our results, based on cumulative catch distribution, catch comparison, and usability indicators, showed that the industry can successfully develop gears with more suitable catch profiles than the one currently used. However, one modification to the codend, the increased circumference, had the opposite effect than expected by the industry. Having the industry as the main driver in the development of new fishing gears can facilitate the development of a larger number and more specialized technical solutions. However, an early and continuous involvement of scientists in the process is crucial, as it ensures that unnecessary and adverse modifications are not made to the gear.

The following article, Veiga-Malta, T., Feekings, J., Herrmann, B. & Krag, L.A. (2018). When is enough, enough? Quantifying trade-offs between information quality and sampling effort for fishing gear selectivity data. PLoS ONE , 13(6), e0199655. https://doi.org/10.1371/journal.pone.0199655, can be retrieved at https://doi.org/10.1371/journal.pone.0199655 . ; There is general pressure throughout the world's fisheries for the industry to have greater involvement not only in the development of fishing gears but also in the testing and documentation of their effect. In the European Union, the Common Fisheries Policy of 2013, together with the proposed reform of the technical measures regulation, highlights the need for greater flexibility in fisheries through increased stakeholder involvement. To achieve this flexibility, there is a need for additional fishing gears available to the fishermen. A way to facilitate this is to have the industry take part in the development and testing of fishing gears, as well as collect data on their performance. However, to have a successful industry-collected data programme, fishermen have to be able to collect data on the length of a portion of the catch. In this study, we determine how many individuals need to be measured to correctly evaluate the relative selective performance of a new gear compared to a standard gear. The evaluation was carried out by analysing catch ratio curves, their associated uncertainties, and the trade-offs between uncertainties and sampling effort. Results show that with relatively small sample sizes (500 to 1000 individuals) it is possible to correctly evaluate the performance of a gear for a given species. By having the industry develop and test their own gears, as well as being involved in the collection of data, the number of potential gear solutions available to address the different issues emerging in the fisheries is increased.

There is general pressure throughout the world's fisheries for the industry to have greater involvement not only in the development of fishing gears but also in the testing and documentation of their effect. In the European Union, the Common Fisheries Policy of 2013, together with the proposed reform of the technical measures regulation, highlights the need for greater flexibility in fisheries through increased stakeholder involvement. To achieve this flexibility, there is a need for additional fishing gears available to the fishermen. A way to facilitate this is to have the industry take part in the development and testing of fishing gears, as well as collect data on their performance. However, to have a successful industry-collected data programme, fishermen have to be able to collect data on the length of a portion of the catch. In this study, we determine how many individuals need to be measured to correctly evaluate the relative selective performance of a new gear compared to a standard gear. The evaluation was carried out by analysing catch ratio curves, their associated uncertainties, and the trade-offs between uncertainties and sampling effort. Results show that with relatively small sample sizes (500 to 1000 individuals) it is possible to correctly evaluate the performance of a gear for a given species. By having the industry develop and test their own gears, as well as being involved in the collection of data, the number of potential gear solutions available to address the different issues emerging in the fisheries is increased.

Five modified trawl codends were assessed for their utility in simultaneously improving the size selectivity of cod (Gadus morhua) and plaice (Pleuronectes platessa) in the Baltic Sea. The modifications included refining the selective performance of the current Bacoma codend by increasing the mesh size of the lower panel from 109 mm double twine to 129 mm single twine and increasing the mesh size in the upper square mesh panel from 132 to 147 mm, and also making the lower panel the same design as the upper panel; i.e. a full square mesh codend. These three experimental designs were tested in conjunction with the currently legislated codends; Bacoma and T90. The most favourable selective properties with regard to simultaneously improving the selectivity for round and flatfish, considering the current minimum landing sizes (MLS) for cod (38 cm) and plaice (25 cm) in the Baltic Sea and the fish population size structures during the sea trials, were found to be the T90 codend and the Bacoma codend with a modified lower panel. For the T90 codend, the selection parameters (L50 and SR) were 43.4 and 6.7 cm for cod, and 24.7 and 2.1 cm for plaice. The selection parameters for the most effective modified Bacoma codend were 41.1 and 8.3 cm for cod and 25.2 and 3.9 cm for plaice

One of the most effective ways to alter catch and length compositions in trawls is to adjust the meshsize or add selective devices such as sorting grids and selective netting panels. These changes are oftenintroduced into the fishery in a top down manner whereby fishermen are forced to comply with spe-cific legislation. However, fishermen have also introduced gear modifications that have contributed toimproving species selectivity in trawls. One of the simplest and most effective modifications that camefrom industry was the development and introduction of twin and multi-rig trawls. Here we analyse catchrates of four target species, Norway lobster (Nephrops norvegicus), cod (Gadus morhua), plaice (Pleuronectesplatessa) and haddock (Melanogrammus aeglefinus), to try and understand how the use of multi-rig trawlshave altered catch rates within the Danish demersal trawl fishery over the last 16 years (1997–2012).Results showed that catch rates of Nephrops in multi-rig trawls were significantly higher (1.89–2.03)than those in single trawls. For cod, haddock and plaice there was no significant effect of gear type. Theresults are discussed in relation to the Common Fisheries Policy reform and the increasing importanceof industry introduced gear modifications

There are numerous examples from across Europe where collaborative science-industry initiatives, which provide a bottom-up approach to trawl gear development, have been successful in developing selective gears. For fishers, the collaborative approach creates a sense of ownership and control over the gears developed and often a greater desire for them to achieve their objectives. Despite the many benefits of collaborative initiatives, a lack of clarity and transparency, incorrect incentives, unclear communication, and distrust or diverging perceptions can inhibit their performance. The present review examines the different collaborative approaches to fishing gear development that have been established within Europe, highlighting their salient features, comparing their objectives, and discussing the types and effectiveness of the incentives offered. Also examined is how the reform of the European Union's (EU) Common Fisheries Policy (CFP), together with the proposed reform of the technical measures framework, can potentially improve the flexibility in the technical regulations and allow for such initiatives to be a central part in improving the state of fish stocks throughout the EU. Finally, a framework is proposed on how initiatives pertaining to industry-led fishing gear development might look like under the reformed CFP.

Rigid fisheries management frameworks often leave fishers with limited possibilities and incentives to adjust the selectivity of their gears to the specific fishing conditions. Implementation of the landing obligation in European fisheries emphasizes fishers need to flexibility in which gear to use to be able to match the selectivity of the gear to the quota available. How fishers can play an important role in facilitating a more regionalised and flexible technical regulation by actively participating in the development of gears and contributing to the scientific documentation of their selectivity is discussed. Perspectives in the proposed technical regulation for EU fisheries and the regionalisation in the 2013 Common Fisheries Policy are discussed based on an analysis of the current EU technical regulation. Then is discussed a new pathway to address the problem, currently being trialled in Danish fisheries. Throughout the article, three themes are discussed: Identifying gear needs, development and testing of gear with fishers as central actors; how the selectivity of the gear should be documented; and opportunities for faster evaluation of new gear, following the regionalisation of the technical measure regulation. The paper concludes that a more flexible system of gear development and evaluation is possible by a) involvement of fishers in proposing gear adjustments, self-sampling and documenting results following scientific protocols and evaluation, testing a range of designs before scientific testing, and b) open for faster approval of gear use under a regionalised technical regulation regime with yearly adjustments of management plans containing the technical regulation.

Discarding keeps being an important issue in world fisheries; it is a way for fishers to adjust their landings to the legal and market constraints, but is largely considered as a waste of rare natural resources and as contributing to the depletion of stocks bearing a high fishing pressure. Many jurisdictions, including the European Commission, are preparing regulations to reduce or ban discards. To design effective regulations, an understanding of the extent and processes of the issue is required. The MariFish BADMINTON project aimed to build up the knowledge of discarding patterns and factors in European fisheries, evaluate the efficacy of selective devices and other discard management measures that have been implemented in the past, and improve methods to analyse, monitor, and manage bycatch and discarding. Specific objectives included the provision of discard estimates for selected European fisheries, and of appropriate indicators; the determination of the most important factors affecting discard amounts and composition; and the elaboration of integrated management approaches to the discard issue. BADMINTON relied on two types of approaches to fulfill these aims and objectives. First was the analysis of onboard observer data, since intensive collection of catch and discard data onboard commercial vessels has been undertaken in European countries under the European Union Data Collection Regulation (2002) followed and intensified by the Data Collection Framework (2008). Thus, one significant contribution of the project was to collate onboard observer data from several European Union member states, given the many differences between national onboard observer programmes sampling schemes, protocols, details of data recorded, and data storage formats. This first step paves the way towards a future better integration of national onboard observer programmes. The second approach was to conduct stakeholder interviews and expert consultation, which was meant to complement the data analyses with fishers perspectives on the discard issue, and to provide an integrated approach toward management. Both approaches lead to the following two broad conclusions: • Discard patterns exhibited high diversity across regions, countries, gear types, vessel sizes, and species, with variability being more pronounced among regions. Thus, discard management approaches might be devised at a regional level – consistent with the proposed regionalization of the currently discussed reform of the European Union Common Fisheries Policy. • Discards amounts, patterns, and composition, are determined by a multitude of interacting natural and human (economic and social) factors in a given place and time, and usually no simple explanations can suffice. The latter affects the effectiveness of mitigation measures, and solutions are to be found down at a very detailed level such as the fishing operation, fishing trip, or vessel, which suggests that a bottom-up, or results-based approach seems to be the most advisable form to tackle the discards problem. Then, effective discard management strategies should be devised at various scales, from individual fishers implementation of detailed species-, gear- and area-specific tools, to producer organizations, member states, regional levels, and the broad European Union. The project has developed a number of tools, distinguished in three categories ie. selectivity related tools (including a modelling tool to estimate gear selectivity based on fish morphology, and preliminary indicators of fishing selectivity at the fleet and ecosystem scales), tools to appraise and understand the discarding issue in a given region, area or fishery (including modelling tools to establish catch and discard maps and devise spatial approaches to the management of discards, based on onboard observer data; a series of discard indicators embedded in a discard indicator dashboard, to monitor and manage the discards in a given fishery; a generic model to determine the relative importance of inferred discard drivers; a list of factors to be used in semi-structured stakeholder interviews, and interview methodology), and tools that can be used to assist in devising management strategies at various scales (including a framework to develop a fishery-specific mitigation strategy based on inferred drivers of discarding behaviour; a detailed evaluation of 12 discard mitigation measures, alone and in combination). It should be underlined, however, that BADMINTON findings suggest that as discarding is in most cases an unavoidable consequence of a series of constraints on the fishing activities and production, managing discards implies taking account of the whole fishery management system. Hence, a discard management strategy should not include only a combination of discard mitigation measures; if discards are to be reduced, appropriate and consistent incentives need to be mended together