The decline of mussel aquaculture in the European Union: causes, economic impacts and opportunities

The decline of mussel aquaculture in the European Union: causes, economic impacts and opportunities Lamprakis Avdelas 1 , Edo Avdic-Mravlje 2 , Ana Cristina Borges Marques 3 , Suzana Cano 3 , Jacob J. Capelle 4 , Natacha Carvalho 5 , Maria Cozzolino 6 , John Dennis 7 , Tim Ellis 8 , Jos´ eM.Fern´ andez Polanco 9 , Jordi Guillen 5 , Tobias Lasner 10 ,V´ eronique Le Bihan 11 , Ignacio Llorente 9 , Arie Mol 12 , Simona Nicheva 13 , Rasmus Nielsen 14 , Hans van Oostenbrugge 12 , Sebastian Villasante 15,16 , Svjetlana Visnic 17 , Kolyo Zhelev 13 and Frank Asche 18,19 1 Ministry of Environment and Energy, Athens, Greece 2 Fisheries Research Institute of Slovenia, Ljubljana, Slovenia 3 Direc¸ ˜ ao-Geral de Recursos Naturais, Seguranc¸a e Servic¸os Marı´timos (DGRM), Lisbon, Portugal 4 Wageningen Research, Yerseke, The Netherlands 5 European Commission, Joint Research Centre, Ispra, Italy 6 NISEA, Fisheries and Aquaculture Economic Research, Salerno, Italy 7 Bord Iascaigh Mhara (BIM), Cork, Ireland 8 CEFAS, Weymouth, UK 9 University of Cantabria, Santander, Spain 10 Th¨ unen-Institute of Fisheries Ecology, Bremerhaven, Germany 11 University of Nantes, Nantes, France 12 Wageningen Economic Research, The Hague, The Netherlands 13 Executive Agency for Fisheries and Aquaculture, Burgas, Bulgaria 14 Department of Food and Resource Economics, University of Copenhagen, Copenhagen, Denmark 15 Department of Applied Economics, University of Santiago de Compostela, Santiago de Compostela, Spain 16 Campus Do Mar-International Campus of Excellence, Santiago de Compostela, Spain 17 Ministry of Agriculture, Zagreb, Croatia 18 Institute for Sustainable Food Systems and School of Forestry Resources and Conservation, University of Florida, Gainesville, FL, USA 19 Department of Industrial Economics, University of Stavanger, Stavanger, Norway Correspondence Jordi Guillen, European Commission, Joint Research Centre Ispra Sector, TP 051, Via Enrico Fermi 2749, Ispra (VA) 21027, Italy. Email: [email protected] Received 17 March 2020; accepted 5 June 2020. Abstract In contrast to the increasing aquaculture production of mussels worldwide, production in the European Union (EU) has shown a decreasing trend over the last two decades. Aquaculture production of mussels in the EU peaked in the late 1990s at more than 600 000 tonnes; by 2016, production volume had dropped by 20% to 480 000 tonnes. As mussel production represents more than ⅓of EU aquaculture production, this decrease is an important contributor to the stagnation of EU aquaculture. Previous studies have suggested diseases, lack of mussel seed (spat), and low profitability as the main causes of the EU mussel production decrease. In this study, we investigate how economic and environmental factors have contributed. Moreover, we examine if the different mussel production techniques (raft, longline, on-bottom, and ‘bouchot’) have been differently affected, by analysing the economic performance and cost structure evolution for the period 2010–2016. We complement these results with a SWOT (strengths, weaknesses, opportunities, and threats) analysis of the EU mussel sector based on expert knowledge. Key words: access to space, atomization, economic performance, environmental factors, low impact, swot analysis. ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 91 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Reviews in Aquaculture (2021) 13, 91–118 doi: 10.1111/raq.12465 Introduction World mussel aquaculture production has been increasing steadily since the 1950s to reach 2 million tonnes in 2016, valued at 3.8 billion USD (€3.4 billion) (FAO 2019). Almost 94% of the world mussel production comes from aquaculture. The main mussel aquaculture producing countries in 2016 were China (43%), Chile 15%, Spain (11%), Thailand (6%), New Zealand (5%), Italy, France, Korea Rep. and the Netherlands (all four countries with about 3%), and with Europe contributing about 20% of total production. However, while European countries like Spain, Italy, France and the Netherlands are still significant producers, European mussel aquaculture production peaked at 600 000 tonnes in the late 1990s and has since decreased to 480 000 tonnes (valued at €420 million, or $465 million 1 ) in 2016 (Fig. 1). Mussel production represents more than ⅓of EU aquaculture production. Consequently, the mussel production decrease is key as it contributes to the stagnation of EU aquaculture and risk of failure to achieve the EU 2020 aquaculture production goals (Guillen et al.2019a). There is not a single cause to explain the mussel production decline in the EU. Mussel production is thought to have declined due to the spread of diseases, algal blooms, lack of spat, predation and low earnings. Such causes may have been exacerbated by local conditions such as the small size of mussel enterprises (Villasante et al. 2013; Theodorou & Tzovenis 2017), the lack of innovation in the mussel production processes (Labarta & Fern´andez-Reiriz 2019), the carrying capacity of the ecosystems to support the mussel production (Villasante 2009) and the impacts of climate change ( ´ Alvarez- Salgado et al. 2009; Rodrigues et al. 2015; Outeiro et al. 2018). Therelativesimpleproduction technology also gives producers limited control of the production process, leading to fewer opportunities for innovation and productivity growth that are the main factors in the growth of aquaculture production in general (Asche 2008; Kumar & Engle 2016; Garlock et al. 2020), and makes production area-intensive. In this study, we investigate economic and environmental factors that may have contributed to the decrease in EU mussel production, and whether the different mussel production techniques have been differently affected. The paper is structured with: a section on EU mussel aquaculture detailing the main farming techniques; a methods section where the main data sources and indicators are defined and presented; the results section that estimates the economic performance and cost structure evolution by production technique for the period 2010–2016; and a SWOT (strengths, weaknesses, opportunities and threats) analysis of the EU mussel sector based on expert-knowledge and summarized by country in the Appendix 1. The paper ends with a discussion and conclusions that build from the analyses of EU mussel aquaculture. The EU mussel aquaculture sector Mussels have been harvested from wild beds in most coastal European countries for food, fishing bait and as fertilizer for centuries (Voultsiadou, Koutsoubas, & Achparaki 2010). Mussel aquaculture based on gathering wild juveniles and moving them to on-grow in safer places had started by the Middle Ages. Nowadays, wild seed mussels are still gathered in several countries, although new spat collecting techniques (e.g. using ropes or shells as a substratum for the planktonic larvae to settle on) have been developed. Additionally, in some European countries, hatchery techniques have been implemented enabling spat (including polyploid) production (Piferrer et al. 2009; Kamermans et al. 2013). According to FAO data, four countries (Spain, Italy, France and The Netherlands) accounted for the bulk of EU mussel production (82% by weight and value) in 2016 (Fig. 2). Four main mussel culture techniques are used in the EU, two being suspended and two being associated with the sea-bed as described as follows: •Raft culture: A raft is a floating platform with suspended ropes of around 30 m which can be folded in the form of a matrix according to the depth where the platform is located. Seed mussels are attached to the rope and covered with a net that progressively disappears as the mussels attach to the rope in a natural way. Every row in the matrix corresponds to a particular harvest, which will be collected and replaced at an appropriate time to maintain a continual production throughout the year. •Longline culture: A horizontal longline rope is suspended by a series of small anchored floats, and ropes or socks of mussels are hung from this rope back-bone. Longline culture is the most recent development for mussel culture and is often used as an alternative to raft culture in more exposed areas subject to higher wave energy. •Bottom culture: This is based on the principle of transferring mussel seed (spat) from areas where they have settled naturally to areas where they can be placed at lower densities to increase growth rates, facilitate harvest and control predation. Bottom cultivation uses beds or poles fixed in the bottom where the mussels are deposited or attached. •‘Bouchot’ culture: This technique uses vertical pilings or poles (known in French as ‘bouchots’) implanted into the inter-tidal sea-bed. Ropes, on which the mussels grow, are tied in a spiral on the pilings with mesh preventing the mussels from falling and from predation. The four farming techniques have different needs and efficiencies. Production efficiency (i.e. mussel production 1 The exchange rate between the USD/EUR was 1.1069, according to the European Central Bank. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 92 L. Avdelas et al. per volume of spat) is related to the differences in mortality and growth rate. It increases from bottom culture to ‘bouchot’ culture, to longline and raft culture (Kamermans & Capelle 2019). Growth rate of mussels is higher in off-bot- tom cultures, and higher when mussels are continually submerged than in inter-tidal zones (Kamermans & Capelle 2019). Rafts require a minimum depth of 8-10 m to be efficient (FIgueiras et al. 2002; Labarta & Fern´andez Reiriz 2019). Longlines require larger areas that are not always available due to competing water usages; however, it does enable mussel culture in shallow waters where rafts would not be suitable. While on-bottom techniques solve some of the problems with required surface space for longlines, they are not as efficient as rafts. ‘Bouchots’, however, do need an extensive inter-tidal zone. Galicia (North-west of Spain) is the most important mussel producing area in the EU, with rafts as the dominant technique. Rafts are also used in Slovenia and the French Mediterranean. Bottom culture is mostly used in Northern European countries: the Netherlands, Germany and Ireland. Longlines are used in Italy, Greece, Denmark, Ireland, Bulgaria and Spain. The ‘bouchot’ technique is mostly used in France and is the predominant cultivation system for the English Channel and Atlantic areas (Fig. 3). Materials and methods Theeconomicdataformusselaquaculturewerecollatedfrom the Economic Performance of the EU Aquaculture Sector Report (STECF 2018) for those countries that reported data by segment for the period 2010–2016. In particular, the following variables were collated: number of enterprises, total value of assets, total employment, employment measured in full time equivalents (FTE), total sales volume, turnover, other Figure 1 Evolution of mussel aquaculture production by weight (million tonnes) in the EU and the rest of the world (1950–2016). Source: own elaboration from FAO (2019) data. ( ) Q rest of the World; ( ) Q EU. Figure 2 Mussel production by weight and value by EU Member State in 2016. Source: own elaboration from FAO (2019) data. Weight: ( ) Spain; ( ) Italy; ( ) France; ( ) Netherlands; ( ) Greece; ( ) Others. Value: ( ) Spain; ( ) France; ( ) Netherlands; ( ) Italy; ( ) Germany; ( ) Others. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 93 The decline of the EU mussel aquaculture income, personnel costs, imputed value of unpaid labour, energy costs, repair and maintenance costs, livestock costs, other operational costs and annual depreciation. This report provided data from eight EU mussel producing countries: Denmark, France, Germany, Ireland, Italy, the Netherlands, Slovenia and Spain. Data by country were aggregated at the segment (production method) level. Hence, the longline technique reflects the combined data from Denmark, Ireland and Italy; bottom technique the combined data from Germany, Ireland and the Netherlands; raft technique the combined data from Slovenia and Spain; and ‘bouchot’ data from France. According to FAO (2019), these eight countries represented 91% of the weight and 78% of the value of EU mussel aquaculture production in 2016. The following economic performance indicators were then estimated based on STECF (2018): Gross value added ðGVAÞ¼turnover þother income energy costs repair and maintenance costs live stock costs other operational costs (1) Earnings before interest and taxes ðEBITÞ¼ turnoverþother incomewages and salariesimputed value of unpaid labour energy costs repair and maintenance costs livestock costs other operational costs annual depreciation (2) GVA margin ¼GVA=turnover (3) EBIT margin ¼EBIT=turnover (4) Mean wage ðgrossÞ¼ðwages and salaries þ imputed value of unpaid labourÞ=FTE (5) Labour productivity ¼GVA=FTE (6) Employees per enterprise ¼Total employees= Number of enterprises (7) Part time share ¼FTE=Total employees (8) Unpaid share ¼imputed value of unpaid labour= ðwages and salaries þimputed value of unpaid labourÞ (9) STECF (2018) data and analyses were complemented with a SWOT analysis of the EU mussel sector summarizing the expert knowledge. This national expert knowledge was used to produce the country profiles in the Appendix 1, aiming to provide further insights for the main EU mussel producing countries, including those for which economic data were not reported here and also to provide qualitative explanation to the observed changes over time. Results Economic performance GVA and EBIT of mussel aquaculture in the EU show a decreasing trend since 2010, while sales volume and turnover indicate more variation and a less clear decreasing trend. The eight EU countries analysed accounted for more than 430 000 tonnes of mussel production in 2016 valued at €328 million. GVA for 2016 is estimated to be €214 million and EBIT €77 million (Fig. 4). The average price at farm gate was €0.82 per kg, with a minimum price of €0.72 per kg in 2015 (€0.76 per kg in 2016) and a maximum price of €0.96 per kg in 2013, when production reported its minimal level. The average price has decreased by 12% between 2010 and 2016, whilst the average production cost was €0.67 per kg, also decreasing 12% during the 2010–2016 period (see Table 1). All mussel farming techniques are characterized by the absence of feed costs because mussels feed by filtering natural food from the seawater. Nevertheless, the differences between the four production techniques result in different cost structures. Costs relatively to total income increase over time for the bottom and raft techniques, leading to a decrease in the economic performance; while for ‘bouchot’ there was an economic recovery in 2015 and 2016, while for longlines profitability seems low for the whole period (see Fig. 5). Figure 3 Mussel production in weight in the EU by technique in 2016. Source: own elaboration from STECF (2018) data. ( ) Rafts; ( ) Longline; ( ) Bottom; ( ) Bouchot. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 94 L. Avdelas et al. Labour is a main cost component for all the production techniques. Wages and salaries reflect the costs to remunerate the employees, while the imputed value of unpaid labour reflects the opportunity cost of labour for unpaid workers. Imputed value of unpaid labour is a cost category with significant differences between the production techniques. This is related to the legal form of the enterprise: raft and ‘bouchot’ techniques record most businesses as personal and family-owned, in which other members of the family randomly or periodically contribute to the activity without a formal contract or salary. In contrast, the longline and bottom segments are mainly composed of relatively large and professionalized companies where such informal labour is limited. This is also reflected in the importance of the unpaid share in the total employment in each technique, as shown in Table 1. Energy and repair and maintenance costs are higher for bottom and longline techniques. In the bottom technique, most EU enterprises have at least one vessel (45 m average length), meaning that capital investment is high compared to other techniques such as rafts, as shown by the total value of assets per enterprise in Table 1. The importance of livestock costs reflects the scarcity of spat, the different ways the mussel industry is trying to obtain them, and how they are accounted. The high livestock costs in the longline technique are because the Italian livestock costs include the salaries of the persons involved in seed collection by scraping rocks in rocky shores. In the bottom mussel industry, where boats must search harder and longer for seed mussel beds, they are often reflected in the energy costs. Other operational costs may include the mussel seed collector costs (if not directly reported under livestock costs) and the annual payment for licenses and concessions for the area where the mussels are farmed. Hence, the average enterprise characteristics for each production technique vary significantly. Bottom enterprises have a high production, achieving a turnover close to €1M per year; while in the raft techniques, enterprises have an average annual turnover below €50 000 per year. Similar differences occur in labour productivity, where productivity in bottom culture enterprises is more than five times higher than in raft culture enterprises. These differences in labour productivity across techniques reflect the different labour and capital intensity across production techniques. In the bottom culture, production is based on a high input of capital; while in other techniques, the production is more labour intensive. Labour productivity shows high inter-annual variations as well over time. These variations are not explained by changes in the workforce, but reflect the natural variation in mussel production due to unstable seed abundance. Despite this overall decrease in economic performance, all culture techniques remain profitable on average during the period analysed. Therefore, the reduction in profitability does not seem to be the origin of the decline in mussel production. Hence, it is necessary to investigate what are the potential factors behind this decline 2 . Figure 4 Sales volume, turnover, GVA and EBIT by farming technique for the period 2010-2016. Source: own elaboration from STECF (2018) data. ( ) Mussel Bouchot; ( ) Mussel Raft; ( ) Mussel Longline; ( ) Mussel Bottom. 2 Production of other types of shellfish such as oysters has also declined (Botta et al., 2020). Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 95 The decline of the EU mussel aquaculture SWOT analysis The EU aquaculture production of mussels has been decreasing over the last two decades and the sector overall seems far from reaching its potential, despite production increases in some countries. The overall farmed mussel production decrease is a result of several factors, often interrelated, that are discussed in this section. Opportunities for the EU farmed mussel sector that could help to improve its economic performance were identified via literature review and brainstorming. This brainstorming was done based on expert knowledge, covering main EU mussel producing countries, as can be seen from the country profiles. The SWOT analysis (Table 2) of the EU mussel sector summarizes the country profiles within the Appendix 1. The relevance of the different factors (strengths, weaknesses, opportunities and threats) is weighted according to the grading 3 given by the experts. Weaknesses The main weaknesses identified that prevent growth in the EU mussel sector are the low price of mussels, the atomization of the producer sector, the lack of suitable space to enlarge or establish new farms and the difficulty to obtain permits. Low prices. Ex-farm mussel prices in most EU countries are relatively low and have been stagnant for some years. In some countries, this is mainly due to the atomized primary producer sector (i.e. many small enterprises), who have little involvement in the secondary purification and marketing phases; this hands the market and bargaining power to the processing and depurating sector (see for instance, Girard & Mariojouls 2008). Another important reason for the low price at the ex-farm level is the import of cheaper products from outside the EU (see for instance, Surathkal & Dey 2019). For example, depurating enterprises in Spain often import mussels from Chile (Labarta & Fern´andez Reiriz 2019). Chile has become the main mussel exporter into the EU, with Spain directly receiving 1/3 of the almost 40 000 tonnes imported in 2017 (Globefish 2018). The opportunity to import low price mussels enables the processing and depurating sector have the bargaining power to offer low prices to the local EU producers. This could be solved via producer organizations (horizontal integration) that integrate vertically in the value chain (e.g. by acquiring depuration or processing factories). There are already some successful cases of integration ‘production–- marketing’ and more recently ‘production–processing–marketing’ in the Galician (Spain) and Italian mussel sectors (see for instance, Friðriksson & Haraldsson 2018). Integration has also allowed the development of new business strategies and product diversification, e.g. basic product (without certifications), organic product and product with recognition of Protected Designation of Origin (PDO). Access to space. Difficulties to access to space for expansions or new farms may prevent mussel production growth, in particular considering that mussel production is often extensive (i.e. demands more space) than other aquaculture production. Location desirability for a mussel farm depends on several factors, such as the distance to port, natural productivity and predation of mussel (Mongruel & Th´ebaud 2006). Coastal space is busy and under increasing demand. It is possible that the most suitable space may Table 1 Performance indicators for the EU mussel aquaculture, average for 2010–2016 Variable Unit Raft Longline Bouchot Bottom Number of enterprises # 2039 247 338 96 Turnover per enterprise €37 194 251 033 382 462 865 314 Total value of assets per enterprise €81 168 387 093 660 854 1 664 188 Employees per enterprise # 5.2 6.2 5.8 2.3 FTE/employee (%) % 25 78 65 75 Unpaid share (%) % 68 7 50 2 Mean wage (gross) €15 037 18 110 30 335 45 810 Labour productivity €23 794 28 796 78 984 149 349 Average production cost per kg €/kg 0.31 0.62 1.65 0.90 Average farm-gate price per kg €/kg 0.37 0.66 2.04 1.25 GVA margin (%) % 76 52 78 59 EBIT margin (%) % 27 19 48 40 Abbreviations: FTE, full time equivalents. Source: own elaboration from STECF (2018) data. 3 The grading of each factor is weighted by the estimated impact on production and the country’s mussel production. The estimated impact is weighted as follows: without impact: 0; low impact: 1; medium impact: 2; high impact: 3; and very high impact: 4. While the mussel production is weighted according to the following criteria: more than 100 000 tonnes: 5; between 50 000 and 100 000 tonnes: 4; between 25 000 and 50 000 tonnes: 3; between 10 000 and 25 000 tonnes: 2; and less than 10 000 tonnes: 1. The total score of each factor is divided by the maximum score obtained, so that each factor is graded between 0 and 1. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 96 L. Avdelas et al. already be taken by aquaculture farms or other activities (Smaal 2002). For example, the production of mussels from rafts in Galicia reached a limit several years ago, due to the lack of additional available suitable space for new rafts 4 . Marine spatial planning, on-going offshore initiatives and multiple use management (Galparsoro et al. 2020) are three potential solutions (opportunities) to mitigate the lack of suitable space for aquaculture. Access to space is perceived as an important weakness in Spain, Italy, Germany, Portugal, Slovenia, the UK, and Ireland. Availability of permits. The administrative burden, the long time this process often takes and the uncertainty of the outcome are significant drawbacks in the process of renewal or issuing of new permits, even if marine space is available for a mussel farm. The uncertainty and time are two factors posing great risk to producers and investors. Uncertainty is often caused by the limited licenses and strict production requirements, partly attributable to political will and conservation regulations 5 . The average time for license renewal varies by country; for example, in Italy it can take from 6 to 18 months, while in Ireland, it can take years. This variability is linked to the Table 2 SWOT analysis for the EU mussel sector with grading (0–1) Negative Positive Internal Weaknesses Strengths Access to space (0.9) Existing markets (1.0) Low price (0.8) Low impact (0.8) Availability of permits (0.8) Clean water (0.6) Atomization (0.7) Incorporate added value (0.5) External Threats Opportunities Harmful algal blooms (0.9) Certification (0.9) Climate change (0.9) Subsidies (0.7) Bad Weather (0.8) Increase consumption (0.6) Diseases (0.6) Diversification (0.6) Predators (0.5) Maritime spatial planning (0.5) Poor water quality (0.4) Going offshore (0.4) Lack of spat (0.4) Multi-trophic aquaculture (0.3) Figure 5 Costs evolution as a share of total income by mussel aquaculture segments for the period 2010–2016. Source: own elaboration from STECF (2018) data. ( ) Profits; ( ) Depreciation of capital; ( ) Wages and salaries; ( ) Repair and maintenance; ( ) Livestock costs ; ( ) Other operrational costs; ( ) Unpaid labour; ( ) Energy costs. 4 For example, the growth rate of mussels on raft in the mouth of the rias is higher than the ones from more inshore rafts (Navarro et al., 1991). 5 For example, in Wexford Harbour (Ireland), traditional bottom mussel producers are being threatened with having one third of their licensed ground removed to be used exclusively as feeding grounds for the local wading bird population. If this is endorsed, already struggling local mussel producers face the prospect of closure. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 97 The decline of the EU mussel aquaculture ability of a country or region to properly handle the bureaucratic, administrative and environmental impact aspects of the mussels sector. Hence, there is still the need to ease and harmonize the administrative burden for new permits. Availability of permits is perceived as an important weakness in Italy, Greece, Germany, the UK, Slovenia and Ireland (longline culture). Atomization. The mussel aquaculture sector is characterized in many EU countries by the atomization of the industry into a large number of small producers. Most of EU mussel farmers are small or microenterprises. This atomization of the producer sector offers the processing and depurating sectors market/bargain power. This could be solved by horizontal integration of these producers into larger producer organizations. Atomization is perceived as an important weakness in Italy, Greece, Denmark, Spain, the UK, Bulgaria and Ireland (longline culture). Strengths The main strengths identified that sustain the EU mussel sector and may support its growth in the near future are the traditional consumption and markets, the increasing tendency to incorporate added value to the mussels produced, the low environmental impact of mussel production and their capacity to clean water and even sequestrate CO 2 . Existing markets. Traditionally, some EU countries (e.g. Spain, France, Italy and Belgium) have high levels of mussel consumption. The consumption of mussels in the EU varies by country, consumption varying from less than 200 g to nearly 4 kg per capita (Monfort 2014). In markets where high volumes of mussels are consumed, it is often easier for local producers to find buyers for their products. As a result of their limited shelf-life, live mussels can only be transported a few hundred kilometres from the coast, requiring a fast and efficient logistic network. The aquaculture sector is more efficient where there is an established and well-functioning seafood value chain (Guti´errez et al. 2020). The existence of traditional consumption and markets is perceived as an important strength in Spain, France, Italy, Greece, Germany, Portugal, Bulgaria, Croatia and Slovenia. Low impact (Eco-friendly). Hall et al. (2011) highlighted mussel farming as one of the least impactful methods to produce animal-source food, across a range of global/regional environmental indicators (eutrophication, acidification, climate change, space use, energy demand, biotic depletion). Furthermore, mussel aquaculture within the EU does not attract the local environmental and ethical criticisms directed at Pacific oyster Crassostrea gigas and finfish farming (e.g. Naylor & Burke 2005; Shepherd & Little 2014) as it: •grows native species, typically sourced from the locality which therefore match the local genotype; •can be categorized as extensive farming of species low in the food chain using natural in situ food resources. It does not require external feed inputs that use industrial fishery products (fishmeal/fish oil), and cause nutrification of the water column via excreted nitrogen and phosphorous wastes; •does not involve use and discharge of medicinal or antifouling treatments; •has not been associated with the amplification of pathogens that may then infect wild stocks; •typically, does not require the control of higher vertebrate predators; and •farms insentient invertebrates which do not merit animal welfare concern. The issue of whether mussel farming does result in a net sequestration of carbon dioxide is subject of scientific debate (Bunting & Pretty 2007; Munari et al. 2013; Filgueira et al. 2015). In Italy, it has been awarded the first certificate of carbon credits for the CO 2 uptake in the shells of mussels during the production process. A pilot project has accounted for the CO 2 emissions in the mussel farming activities, showing that mussels absorb CO 2 . This opens a new potential market, where mussel farmers can produce ‘green’ certificates for the volume of the CO 2 sequestrated and sell them to enterprises that are responsible of CO 2 emissions and need to buy such permits. However, as with any food production, mussel farming cannot be considered completely benign and various local environmental impacts have been suggested or demonstrated (Kaiser et al. 1998; Beadman et al. 2004; McKindsey et al. 2011; Science for Environment Policy 2015). These include aspectssuchasculturesystemsaddingphysicalstructuresto the environment which entrap wildlife and affect currents, sedimentation and light; removal of plankton; organic enrichment of the sea-bed via pseudo-faeces reducing biodiversity and abundance; movement of spat transferring indigenous and non-native pest species; spat collection (including dredging) removing wild individuals and affecting habitat and ecology. Nevertheless, judgement of such impacts needs to be balanced against potential local environmental benefits (Edebo et al. 2000; Jeffery et al. 2014; Suplicy 2020) which include structures providing shelter and habitat, and feeding reducing eutrophication. The low impact of mussel production is perceived as an important strength in Germany, UK, Croatia, Slovenia, Spain and Denmark. Capacity to clean water. Shellfish aquaculture is the only human food production system that does not release pollutants from farming, but removes them from their production environment. Mussels and other filter feeders improve Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 98 L. Avdelas et al. the water quality and clarity, making the marine ecosystem more suitable for organisms (Borthagaray & Carranza 2007). This gives the possibility of developing aquaculture for human consumption or for water purification (Lindahl et al. 2005; Lindahl & Kollberg 2008). When filter feeders are grown only for water purification, the product is normally reserved for use as agricultural fertilizer or animal feed. Otherwise, nitrogen and other pollutants, which remain in the shellfish meat, must be removed after harvest if they are to be suitable for human consumption. Their capacity to clean water is perceived as an important strength in Spain, Italy, Ireland, Bulgaria, Denmark, Croatia and Slovenia. Incorporating added value. In a context of declining natural resources and increasing production costs, adding value to seafood products, and to lesser extent to aquaculture products, is a major concern for producers and public authorities. Traditionally, a large part of the national mussel production has been consumed fresh, while there has also been production of canned mussel (e.g. Spain). With the increase in frozen and canned mussel imports, in recent years, the canning industry has opted for more added value products through a greater degree of processing, especially ready-to-eat products such as boiled mussels (with and without shell) and even prepared dishes of fresh mussels in different sauces. Initially, most of these processed products were not destined for the traditional local markets, but for export. However, their consumption increases year after year in the traditional market as well, due to changes in consumer behaviour. These new products have encouraged and strengthened alliances between producers and canners. In the case of mussels, it can also be important to enhance the traditional mussel offer with certified and organic mussels, as this has been successful approaches for other seafood products as well as food products more generally (Roheim et al. 2018). Threats The economic performance of the EU mussel sector may be challenged by some threats detected mainly at the production level. Harmful algal blooms, bad weather, diseases, predators, poor water quality and pollution may impact the mussel production. Harmful algal blooms (HAB). Algal blooms, i.e. the rapid growth of algae populations, occur mostly due to the excessive amount of nutrients and organic matter in the water (Wells & Karlson 2018). The formation of these blooms often leads to changes in the pH and dissolved oxygen (eutrophication), as well as changes in the water colour due to the algae pigments (e.g. red tides). Harmful algal blooms are events that cause negative impacts to other organisms. Harmful algal blooms are often associated with large-scale marine mortality events and have been associated with various types of mussels and shellfish poisonings (Falconer et al. 1992; Amorim & Vasconcelos 1999; ´ Alvarez-Salgado et al. 2008; Peperzak & Poelman 2008). Thus, when harmful algal blooms occur, mussel producers are not allowed to sell their produce until the mussels are fit for human consumption. This can cause significant economic losses to the farmers (Hoagland & Scatasta 2006; Jin et al. 2008; Ahsan & Roth 2010; Rodrı´guez et al. 2011; Le Bihan et al. 2019; Theodorou et al. 2020), even if the exact impact is difficult to quantify (Rodrı´guez et al. 2011; Sanseverino et al. 2016; Theodorou et al. 2020). The number, intensity and consequences of harmful algal blooms episodes have been increasing (Glibert et al. 2005), which makes it more difficult to predict and effectively respond to these events. Harmful algal blooms affect mainly Spain, Portugal, Italy, France, Greece, Ireland (mostly longline culture), the UK, Bulgaria, Croatia and Slovenia. Climate change and ocean acidification. Since the industrial revolution, human activities emitting greenhouse gases (CO 2 and others) have increasingly affected climate. Climate change has started affecting environmental parameters and more is to come: temperature increase in the ocean, sea level rise, ocean acidification, changes in rainfall and therefore salinity, and the concentration and quality of nutrients (Philippart et al. 2011). The economic damage caused by acidification alone to shellfish production in Europe is estimated to reach US$1 billion annually by 2100 (Narita & Rehdanz 2017). An increase in the number and intensity of extreme weather and harmful algal bloom episodes is also expected. Indeed, the distribution and effects of harmful algal blooms are becoming more common, leading to more frequent and prolonged disruptions of product supply, which can easily result in a loss of market share for the affected production area. Seed mortalities are another indirect effect of climate change, more common in Southern Europe production areas, but also Northern Europe has recently being affected. Climate change is perceived as a major threat in Spain 6 , Italy 7 , France, Greece, Germany, Slovenia and Portugal. 6 For example, Des et al. (2020) show that climate change will lead to less favourable conditions for mussel aquaculture in Spain. 7 Temperature increases, as experienced in the Adriatic region, forces early harvesting of mussels. This implies harvesting mussels with lower meat content. 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Appendix Country profiles This appendix presents country profiles of the EU mussel producer countries, including information on the economic performance evolution, production specificities and main threats to the mussel production. Spain Mussel rafts The mussel industry in Spain, most of it concentrated in Galician rias, represented the 73% of the total Spanish aquaculture production in terms of quantities in 2016. The evolution during 2015 and 2016 illustrates how dependent is the mussel production to the environmental conditions in the Galician rias, where red tides can close the production areas for long periods of time. Annual mussel production reflects high fluctuations over time; in 2016 suffered a decrease of 4.3% respect to 2015 until 215 thousand tonnes. Mussel production in Galicia has been severely affected in 2010, 2013 and 2014 by red ties. The number and intensity of these events have been multiplied by 4 during the decade (from 2000 days of closed polygons of mussel rafts in 2007 to 8000 days in 2016), making the mussel industry more vulnerable to climate change impacts and putting at risk the capacity of the sector to supply the seafood markets (OESA 2017). The production value of this segment was €118 million in 2016, the highest production value during whole period Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 110 L. Avdelas et al. analysed; which represents an increase of 2.4% compared to 2015. This increase is mainly explained due to the growth of prices in 2016 (€0.55/kg), the highest observed price since 2008. This is the biggest segment in terms of employment, with 2610 FTE in 2016, which was 1.5% higher than in 2015; and it also the highest number of people employed in the segment during the period analysed (2010–16). Traditionally, it is a sector where there are a high number of people working a part of the year; most of them are self-employed workers due to the familiar characteristics of these small units. The mussel is cultivated mostly in Galicia, where it is a traditional and consolidated sector with a significant impact on the economy (Labarta & Fern´andez-Reiriz 2019). Most of the people working in the sector are from the local areas. Mussel farming is a family-owned business. OESA (2017) estimated that around 3669 rafts were held by around 2300 families in Galicia. The number of rafts in Galicia has reached a limit several, due to the lack of additional available suitable space for new rafts. Traditionally, mussels in Spain have been marketed fresh or canned. It is important to highlight that the sector is closely related to the canning industry, also situated in the same areas, and in which most of the inputs are from Galicia. In recent years, there have been some initiatives in order to produce new product presentations which more added value through its transformation. Furthermore, there are no external investments in the Spanish mussel sector, but Spanish companies are investing in the mussel industry abroad, such as in Chile (Gonzalez-Poblete et al. 2018). These investments have contributed to the substantial increase in the production (e.g. Chile production of mussels have gone from less than 24 000 tonnes in 2000 to more than 300 000 tonnes in 2016 according to FAO). This has resulted in Chile becoming the main mussel exporter into the EU, with almost 40 000 tonnes in 2017, and Spain directly receiving 1/3 of these imports (Globefish 2018). The establishment of the Regulatory Council of Mussel in Galicia in 1995 led to a significant positive impact on the process of aggregation of producers into producer organizations (2092 rafts being part of about 20 producers organizations in 2018) and promoted the recognition of Protected Designation of Origin (PDO). This has also resulted in some level of vertical integration in the sector (Castelo & P´erez-Dorca 1997). The fresh mussel markets in Galicia (Spain), in which the producer organizations themselves own marketing facilities, combined with the high volumes exported (especially to France and Italy) have transformed the marketing channels in Spain. This led to the increasing incidence of the major retailer chains, mainly Mercadona—who may have sold around 25 000 tonnes of fresh mussels from the Galician Rias—as well as others, such as Carrefour, Eroski and Gadis whose supplier strategy is one of agreements with processing companies, all of which helped to consolidate the fresh mussel market in Spain (Labarta & Fern´andez Reiriz 2019). Italy Mussel longline The mussel sector, as reported in the National Strategic Plan for Aquaculture 15 , is considered very important both in terms of volumes produced and employees. It represents the most important aquaculture segment at national level, in terms of production volume with 47% of sales in 2016 and a turnover of 35% of the entire Italian aquaculture. But mussel farming in Italy is not attractive for future investments, mainly caused to low ex-farm prices and the scarce introduction of best practices that may increase the consumers’ willingness to pay (STECF 2018). Domestic production is not always able to meet the demand, also in relation to the seasonality of the supply that characterizes the national product. Mussel segment, during the 2016, indeed, has a reduction in volume of sales around 30% due to low abundance of commercial product in size. High temperatures caused the product to be caught ahead of time. It has been offered on the market in advance and therefore cuts to smaller and with less quantity of edible meat. Furthermore, high amounts of product were offered concentrated in a short time, so producers were forced to further reduce ex-farm prices, and the turnover, during 2016, decrease more than 25% compared to 2015. Production companies, based on the modest market value of the mussels and the expansion of farming into new areas, must meet the objective of maximizing production efficiency, focusing on the areas in which they deem the conditions most suitable from the point of view of the productivity parameters. The creation of ‘protected’ marine areas for mussels is a goal that is expected to be reached by 2019, in line with the forecasts and actions reported in the national Strategic Plan for Aquaculture. The sector suffers from the inability of the operators to increase the ex-farm price, which is related to the absence of a centralized supply distribution channel. The greatest weakness is the lack of aggregation of supply: the producers are not involved in the purification/depuration and relaying stages of mussels, which compromises the ability to control the price. Only recently, also with the support of the EMFF funds, in some Adriatic regions, companies, mostly producer cooperatives, are starting investments to buy boats equipped with mussel purification plants. The boats are 15 Piano Strategico per l’acquacoltura in Italia 2014-2020 according to Art. 34 ‘Promozione dell’acquacoltura sostenibile’, Reg. 1380/2013/EU on CFP. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 111 The decline of the EU mussel aquaculture more than 18 m long and have the double function of being at the service of the installations and also of bagging the product intended for commercialization. In the last three years, important innovations are taking place in the sector, especially as regards the vertical integration of the production chain. Further interest has been that of being able to sell pre-growth product to other installations both in Italy and abroad. From 2002 to 2016, in Italy the productive dynamics of the shellfish sector show a clear signs of territorial specialization. This has determined the consolidation of an already strong activity since 2002 in some Italian regions, as is the case of the Emilia Romagna region, which passed from an annual production of molluscs (mussels, oysters and clams) of 22 000 tonnes in 2002 to about 52 000 tonnes in 2016 (personal communication of the National President of Mussel Producers). Specifically, for mussels, the Emilia Romagna Region registered the equivalent increase recorded in the broader shellfish segment. The analysis of ex-farm prices of mussels has shown that prices remained almost the same during the last 5 years, though both consumption and consumer prices have gradually increased. In 2016–2017, mussel prices reached more than EUR 2.50 per kg were recorded for mussels with organic certification and for mussels carrying PDO (Cozza di Scardovari DOP) labels. The H2020 Success 16 project investigated the bottlenecks and the opportunities for the Italian mussel sector. It concluded that the Italian mussels sector consists of relatively small companies that have limited negotiation power towards the supermarkets. Producers should produce and merge in consortia and then have one professional seller of their produce which could strengthen the ability to negotiate higher prices. Organic produced mussels do not always fetch higher prices and that makes investments in organic certification more uncertain. Costs for certification in general are not awarded by higher prices in supermarkets. It is a demand for market access today. The bureaucracy should be reduced and speedier. Another limit is the banks—it is hard to get loans for fish farmers. They would like to have the same conditions for approving loans as the agriculture sector in Italy. In case a producer loses his production because of weather conditions or similar, there is not the same compensation between regional authorities as it can vary from 0 to 90%. The authority’s compensations to farmers should be coordinated between regions to be fairer. The feature of the segment, in terms of profitability, or poor capacity to generate revenue, is due to the highly based, low-capitalized structure. The human resources employed are on average below the average number that would be appropriate to make work more efficient (Malvarosa et al. 2017; Success 2017). France Blue mussel (Mytilus edulis) and Mediterranean mussel (Mytilus galloprovincialis), the two cultivated species, represent around 33% in weight, 20% in value of the whole French aquaculture production. Output has varied widely from 60 000 to 94 000 tonnes, valued at between €117 and 172 million over the period. French mussel production is not adequate to meet the national demand. The imports of mussels mainly from Chile, Netherlands and Spain exceed widely the exports revealing a structural trade deficit. Blue mussel represents around 96% of total volume and value of French mussel production. From 2010 to 2016, the price blue mussel varied from €1.83 to €2.02 per kg, with an average price of €1.90 per kg. The most important operational cost items are wages and salaries and the imputed value of unpaid labour, which are higher than the operating costs. The spat supply is exclusively on wild source, so the livestock costs are very limited (9%) and concern only the mussel farmers rearing in the areas where no mussel recruitment exists due to low temperature of water or salinity to much important. Investments are important for this activity. The depreciation of capital item attains 33% of the total costs. Mussel ‘bouchot’ Since 2010, the production of mussel is decreasing. In 2016, mussel production volume is 69 thousand tonnes with a value of €139 million. This decline was due to unfavourable weather causing a deficit of production and poor quality of mussels (2011, 2012). The deficit comes also from the resurgence of predators (sea-star) in some areas of production (Channel and Atlantic coasts). Since 2014, a high mortality of mussels has been located in production areas located in the West of France (Pertuis Breton and bay of Bourgneuf). The mortalities have reached up to 100% on the longline for some professionals and 50-80% of the ‘bouchot’ cultivation system. The causes of these mortalities are difficult to establish (pathological, environmental and physiological) (B´echemin et al. 2015; Robert & Soletchnik 2016; Charles et al. 2020). Given the short cycle of the mussel, producers cannot replenish their stocks and mussel production in hatcheries is not allowed in France. As with a lot of environmental hazard causing shellfish mortalities, the prevention methods or the tools for reducing the economic consequence are limited. Financial difficulties are important (drop in sales, net loss of turnover), while cleaning of leaseholds (remove the 16 Strategic Use of Competitiveness towards Consolidating the Economic Sustainability of the European Seafood sector, project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 635188. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 112 L. Avdelas et al. mussels) causes significant costs. These mortalities are forced certain mussel farmers to dismiss employees or remove the seasonal contracts in order to reduce the costs of wage. That is why the mean wage decrease by 44% between 2014 and 2015. If older companies have cash to cover fixed costs, young companies, much more indebted, have significant difficulties. Measure 56.1.f of EMFF was mobilized in order to compensate the mussel farmers impacted. Since 2015, in Mediterranean, shellfish producers deal with two sale bans due to harmful algal blooms’s (Alexandrium catenella) or norovirus during autumn. The duration of bans can reach 5 weeks among years. Shellfish farmers dread climate change increasing risk of epizootic, the emergence of diseases in the marine environment and the increase of shellfish trade ban due to harmful algal blooms (Dinophysis,Alexandrium,Lepidodenium, etc.). This climate change will affect the environmental parameters: temperature change on ocean acidification, on rainfall and therefore the salinity and the concentration and nutrient quality. This will have consequences on future aquaculture output and on the economic results as in 2011 or 2014 where the EBIT margin decreased sharply. As mussel farming is capital intensive, the fixed costs are high. These costs structure exposes financially the businesses in case of natural hazard impacts. The most important challenge of the mussel farmers is the capacity to cover fixed cost when market bans or production losses occur. The fluctuations of the prices do not always allow to compensate the natural hazard impacts on the level of production. Mussel producers are afraid of the multiplication of natural events occurring either mortalities or market trade bans which over time would question the profitability of their activity. Netherlands Mussel on-bottom Sales volume has oscillated between 36 thousand and 56 thousand tonnes between 2008 and 2016, but sales value has decreased since 2013 due to a decrease in the blue mussel price. Most production is sold in Belgium. This has led to a decrease on the economic performance during the last years. The oscillations in the production volumes are influenced by the collection of mussel seed in the 2–3 years before production sales. Most important costs items include other operational costs (41%), wages and salaries (27%), and repair and maintenance (12%). Within other operational costs, rental costs for the area where the mussels are farmed are important, as well as the costs that relate to the mussel seed collectors. There are competing claims for the most suitable areas (i.e. good growing locations) and operating in Nature 2000 areas, In an agreement with the Dutch Ministry and environmental NGOs, the mussel sector started a transition from wild seed fisheries to sustainable alternatives (mussel seed collectors) in 2020. Although the collectors work quite well and guarantee a quite stable mussel seed production, the work requires a lot of labour. Mussel losses from waves and currents are the major risk factor for farmers. Environmental conditions are becoming more variable and less predictable creating large fluctuations in growth. In addition, recent events of mass mortality in Oosterschelde seem to be due to a disease, even if reasons are not known yet, There is some vertical integration in the supply chain and diversification in larger companies. There will be some pilot projects of offshore mussel aquaculture in the Dutch waters, but no for IMTA. Greece Mussel aquaculture, being the most important shellfish aquaculture in Greece (circa 15% of the annual aquaculture production volume), produces annually 16 thousand to 23 thousand tonnes of mussels valued between €6 million and €8.5 million (Eurostat 2019) 17 . There exist two main ongrowing techniques: the pole system with small farms (500 m 2 ) in shallow (3–5 m) coastal sheltered areas and the longline system in areas with depths greater than 10 m. Mussel spat for aquaculture use is collected from natural populations. According to Avdelas et al. (2015), labour cost (42% including sprat collection), repair and maintenance (19%), energy (17%) and depreciation of capital (11%) are the main cost components of mussel aquaculture. The average mussel price has been relatively stable at a less than €0.4 per kg since 2011, being between the lowest among the EU mussel producing countries (Eurostat 2019). While producers are able to cover the operational costs, profit estimation depends mostly on the assumptions used for the estimation of the opportunity cost for unpaid labour (Avdelas et al. 2015; Theodoridis et al. 2017). Theodoridis et al. (2017) collected data in 2013 and 2014 from three regions (Chalastra, Kymina, and Makrygialos) in the Thermaikos Gulf through a survey of 66 mussel farms. According to Theodoridis et al. (2017), labour cost represented 31%, variable costs including sprat collection (38%) and fixed costs (28%). Theodorou et al. (2014) collected data from eight farms in 2008 and modelled the costs by farm size. According to Theodorou et al. (2014), labour cost represented 25%, variable costs (22%), fixed costs (14%) and 17 However, there are many elements that render these production estimations too uncertain. Uncertainty comes from environmental conditions including harmful algae blooms, temperature, etc., as well as the existence of unlicensed farms. Theodorou et al. (2011, 2014) estimate a total production of 36 thousand tonnes of mussels in 2008. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 113 The decline of the EU mussel aquaculture depreciation (39%) in an average farm of 2 hectare. Although the small size of the farms has been identified as a financial risk (Theodorou et al. 2014), producers seem to take into account mainly the environmental risks and regular supply by producing at multiple small farms in various locations. Approximately 50% to 70% of the annual production is exported mainly to Italy and other EU countries. Mussels are sold live or fresh, and the most common diversification activity is basic processing (de-shelling of mussel bodies). There are no voluntary certified products. The race for nutrients among licensed and unlicensed farms, predators (such as the blue crab in the main production areas) and uncertainty arising both from the current environmental conditions (periods of banned sales mainly due to bio-toxins or presence of toxic algae) and the changing environmental conditions (sea temperature rise) are the main threats faced by the mussel aquaculture in Greece nowadays. Due to the licensing scheme operating in Greece, mussel aquaculture is mainly comprised of small and poorly mechanized farms with low bargaining power and no means to cover the regular supply needs of the modern retail chains. To this end, economies of scale and gains in bargaining power can be achieved both by mergers and acquisitions and by the establishment of producer organizations (Avdelas et al. 2015; Theodorou & Tzovenis 2017). The importance of the internal country market that could match the seasonal production to seasonal demand during the summer in touristic areas is overlooked by the producers who are mostly export oriented. No significant rise of the production is expected in the near future. Research for the identification of suitable farming areas would be needed in order to further develop mussel aquaculture in Greece. Germany Mussel on-bottom The German blue mussel aquaculture takes place at the world heritage and National Park of the Wadden Sea. Therein strict restrictions limit the total number of licenses for harvesting mussel seeds and culture areas (Schlauch 1999). In consequence, the number of enterprises, which are organised in two producer associations, is stable at 11 to ten companies since the 1990s. Nonetheless, the production volume and value have varied a lot in the past. In 2009, there was a unique low of about 4000 tonnes (and a value of around €5 million). A peak of about 22 200 tonnes harvested (and a value of around €25.3 million) happened in 2016. The average landings between 2008 and 2016 have been about 9860 tonnes and €13.20 million. As the overwhelming majority of landings are sold via auction at Yeserke in the Netherlands, German mussel fishers are price takers due to price transmission effects from Netherland harvests. From 2008 to 2016, the price of blue mussel has varied from €0.84 to €2.17 per kg, with an average price of €1.38 per kg. Most important cost items have been repairing and maintenance (23%), other operational costs (22%; including the costs for licenses and the rents for seed collectors from the Netherlands), and wages and salaries (21%) in 2016. Regarding the profitability on micro-level, an income of around one million euro per enterprise or €800 000 per vessel is needed as an average to cover the operating costs 18 . The high variance and unpredictable fall of wild mussel seed, the loss of catching areas through the invasion of the alien pacific oyster (Crassostrea gigas), strict conservation regulations and ocean dumping are identified as the most challenging factors by the mussel farmers. The increased ocean dumping in the recent years is assumed to influence negatively the blue mussels’ growth rate at Lower Saxony’s Wadden Sea. There is no ocean dumping in the parts of the Schleswig Holstein Wadden Sea, where the growth rates of blue mussel cultures are significantly higher. Nonetheless, blue mussel farming can be considered as a profitable business in Germany. The overall economic trend of the German blue mussel segment is—against all listed restrictions—positive. In outstanding good years (e.g. 2016), the gross profit margin can be higher than 35%, which is key to compensate bad years, where the gross profit margin can be negative (e.g. −7% in 2009). Anyway, the decisive question for German mussel cultures has a more political nature: Will future trade-offs between nature protection objectives and mussel producers enable mussel cultures in the National Park of the Wadden Sea in the next decades or not? The difficult and long negotiations for the so-called ‘mussel peace’ in 2015 infer that the existence of mussel production in Germany is first of all the result of a political compromise. Now, until 2030 mussel production licenses are ensured at least for the Northern part of the National Park of the Wadden Sea. Ireland Traditionally, the main production areas for bottom culture are in the southeast and the southwest, and in the southwest for rope culture (O’Sullivan 1998). Rope mussel output has remained within a gentle oscillation, while bottom culture output has undergone a large and overall downward trend over the observed period. Shared limits to economic expansion of both the rope and bottom cultures in Ireland are: i) distance to market and competition with the large domestic production of the countries exported to. ii) Regulation; license applications and 18 Personal communication, Suitbert Schm¨ udderich (CEO COFAD— Consulting Agency for Fisheries, Aquaculture and regional Development, Weilheim) on costs of mussel culture operations. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 114 L. Avdelas et al. renewals are lengthy procedures due to most aquaculture sites being within or adjacent to Natura sites. Producers are subsequently denied access to government grant aid and new grounds. iii) Harsh, unpredictable Irish weather conditions complicate management and can lead to poor growth, poor meat content, stress and mortality, resulting in poor prices. Disease, thus far, is not an issue for Irish mussels. Mussel on-bottom Output has varied widely from 3000 to 17 000 tonnes, valued at between €800 and 1200 per tonne, over the period. Businesses and vessels are mainly local, family owned, providing mainly full-time employment, with significant partnership investment by Dutch companies. The segment is fragmented but groupings will collectively lobby over seed fishing access and resource management in general. Sales are entirely export, predominantly to the Netherlands and France, with some exports to the UK and Italy. The main threat to the segments’ viability is the almost complete reliance on the appearance of wild seed beds for stock input, and these appear to be diminishing over the period as a whole. The already high costs of maintaining, running and crewing sea-going vessels in Ireland are exacerbated by the greater effort required to find wild seed. The limited use of alternative seed sources or collection systems such as those used by the rope culture are probably due to issues of licensing conditions as much as technical difficulty. On the other hand, there are conflicting reports of the negative effects of one bivalve stock presence upon another, with the mussel producers of Castlemaine harbour regarding the neighbouring Gigas oyster producer stock of killing their stock and the opposite accusation made by the oyster producers of Loughs Foyle and Swilly upon their mussel producing neighbours. However, there is no scientific study to back either claim. The future evolution of this segment is as uncertain as the fate of the wild seed beds upon which it continues to depend, the management of which is complicated by the 1965 Vosinage agreement between the UK and Ireland and the unfolding nature of Brexit. Sales price, despite vigorous marketing campaigns to distinguish Irish mussels, struggles to compete with that of its competitors. Mussel longline This segment reliably produces between 8500 and 10 500 tonnes annually of mainly fresh but also processed products exported to France, the Netherlands Italy and elsewhere in Europe, and some half-grown product is occasionally sold to the Bottom mussel segment. This is a fragmented segment, almost entirely family and locally owned, offering mainly part-time or seasonal employment alternatives to agriculture, tourism and fisheries in remote areas, with a significant degree of unpaid labour sustained by the owners themselves. The segment is becoming gradually more capital intensive, overall employment and the number of individual businesses is declining. As the age profile of license holders advances, more and more sites are being leased or transferred to betterequipped and more professional entities. The sector has struggled to remain profitable, despite minimal costs compared to other segments, successful investment in technical innovation and efficiencies, as well as in quality product certifications. There are particular factors limiting Rope mussel production: (i) health and safety: red tide bay closures can be lengthy and can occur at the height of harvest season, disrupting supply, reducing sales value and increasing losses of stock from the lines, (ii) low market price relative to competitors continues, as does the higher costs of getting the exported product to market compared to mainland European competitors and (iii) increasing labour costs. The amount of licensed production ground will not increase significantly, if at all, due to increased competition for limited space and a very successful anti-fish farm lobby. Volume output is expected to remain within the current observed pattern. Continuing efforts to increase the profile and value of Irish mussels abroad and to develop the home market close to production sites is expected to gradually improve sales price. Business amalgamation and declining seasonal employment trends are expected to continue (Cush & Varley 2013). The red tide issue and the resulting tight margins, brought on by relatively high costs and low product unit values, are being combatted by larger companies by acquiring sites in different bays, thereby increasing their capability of maintaining continuity of product supply and unit value even if one or two of their sites are closed by red tide, thereby spreading the risk. UK 19 In 2016, the UK accounted for 3% of EU aquaculture production of mussels. Mussel farming dominates shellfish aquaculture across all four regions of the UK (Scotland, England, Northern Ireland and Wales), with both on-bot- tom, raft and longline techniques being used (Laing & Spencer 2006; Seafish 2019). The main species farmed is the blue mussel (Mytilus edulis) (Laing & Spencer 2006), although the Mediterranean mussel (M. galloprovincialis) and hybrids also occur (Gardner et al. 1993; Dias et al. 2009; Seafish 2019). Much UK production is sold live to northern mainland European countries (Anon 2012), where large-scale facilities exist for depuration. UK 19 In this study, the United Kingdom is analysed together with other EU Member State because the UK was a member of the EU until 31 January 2020. Reviews in Aquaculture (2021) 13, 91–118 ©2020 The Authors. Reviews in Aquaculture published by John Wiley & Sons Australia, Ltd 115 The decline of the EU mussel aquaculture