Sources and Quantities
Global capture fisheries cannot meet demand for scallop due to overfishing and scallop farming has become an increasingly important global aquaculture activity1. Scallops are farmed across the world in cold and warm water regions, and include over ten different species both native and introduced, as shown in the table2.
Scallops are filter feeding bivalve molluscs that live mainly on sand or gravel sea bed from 30-40m deep up to shallow waters, but not exposed at low tide. Large scallop species can have a life-span of up to 20 years. Market value of scallops is closely related to their size however, harvesting farmed scallops at various sizes may be economically preferable depending on the market.
As shown on the map, scallops are farmed across the globe. Globally scallop farming was worth almost US$5.6 billion from a 2016 production total of some 2.1 million tonnes. China produced over 88% of this volume. Other important producing countries are Japan, Peru, Russia, Chile and South Korea which together produced some 11.5% of world production in 20162.
China produces over 80% of the world’s bivalves, but domestically consumes almost all of this production. Less than 5% of total world bivalve production enters international markets; one of the lowest proportions in seafood trade. This is due to the very nature of bivalves, which are highly perishable and potentially pose a risk to human health if not properly handled. The EU is one of the main markets for bivalves taking over one-third of the total bivalve trade Around 150,000 tonnes of scallop are internationally traded per year, and EU scallop imports are around 40,000 tonnes per year3, 4.
Scallop cultivation was developed in Japan in the late 1960s where it rapidly restored production to levels lost through overfishing5. Japanese success has encouraged other countries to cultivate scallops. In China, culture of the local zhikong scallop started in the 1970s, followed in 1982 by Bay scallops imported from the US. For both these species it was not possible to collect wild spat so large-scale hatchery culture was developed, followed by suspended culture in the sea. As zhikong scallop aquaculture increased natural spawning also increased enabling wild spat collection. Today, there is virtually no hatchery production of this species. In recent years there has been a sharp fall in zhikong scallop production caused by summer mortalities. To compensate there has been expanded production of non-native Bay and Japanese yesso scallops6.
Chilean culture of the Peruvian calico scallops started in the 1980s and is based on highly variable natural settlement on collectors, supplemented by hatchery production7. Peru followed similar methods and now exceeds Chilean production. Scallop production in this region can fluctuate widely due to El Niño effects4.
Domestic Market Information8, 9
Over the past ten years (2008 – 2018) sales of scallop have been in growth in Great British retail (i.e. in England, Scotland and Wales), with value up 19% and volume up 11%, respectively from a base of £13.4 million and 666 tonnes in 2008. Scallop sales have grown, despite having one of the highest average prices behind lobster.
In 2018, UK retail sales of scallops were worth £16.6 million (-3.8%), with a volume of 784 tonnes (-3.9% compared to the previous year), in the 52 weeks to 16/06/2018 (including discounters). Average price was £21.23 per kg (+0.1%); ranking as the 20th most popular species by value.
In 2018 the UK imported 1,340 tonnes of scallops.
Note: the difference between the volume of scallops sold in UK retail and that which is imported is due to its use in the foodservice industry (e.g. restaurants) (no data available) and that which is re-exported.
Production Method1, 10, 11
There are a variety of ways in which spat can be collected, including a series of mesh bags suspended in the water column on a line which is anchored to the seafloor (i.e., long-lining). Mesh bags are filled with a suitable cultch onto which scallop larvae will settle. In countries where natural spatfall is poor, or in the case of introduced scallops, spat can be hatchery reared. To prevent high mortality of scallop spat associated with early transfer to grow-out facilities there may be a nursery stage which helps to produce more robust juveniles.
There are two basic methods for scallop grow-out: hanging and bottom culture. Hanging culture relies on rafts or longlines from which scallops are suspended in various water depths and using a variety of techniques as shown in the Yesso scallop grow-out diagram opposite. Bottom culture employs the use of plastic trays or wild ranching on the seabed in shallower waters.
Governance systems play an important part in ensuring environmental sustainability, and whilst these have evolved rapidly with the growth of the industry, there are differences between regions and countries. Poor governance can result in industry stagnation, the spread of preventable diseases, environmental damage and opposition to aquaculture activities by local communities and groups such as non-governmental organisations (NGOs). Key governance responsibilities are ensuring environmental assessment and decision making processes are in place for sensitive and coastal ecosystems, which help deliver sustainable aquaculture whilst managing possible adverse impacts. Other regulatory and governance aspects should cover aspects such as water abstraction and discharge, health monitoring, and so forth.
Four principles – accountability, effectiveness and efficiency of governments, equity, and predictability of the rule of law – are necessary for effective aquaculture governance. These principles should guide the administration, legislative and regulatory framework of aquaculture. In addition to governments, other stakeholders such as communities, non-governmental organisations (NGOs) and producers should also be involved in the governance of the industry1.
The vast majority of scallop production is undertaken in four global regions: Asia-Pacific, Latin and North America, and Europe.
While many countries in Asia-Pacific have made commendable efforts to set up policies, administrative, legal and regulatory frameworks to properly develop and manage aquaculture, some countries in the region are still lagging behind. However, many Asia-Pacific regional countries (e.g. Australia, NZ) enjoy established strong aquaculture governance structures (policies, institutions, regulations, etc.) in support of sustainable development and management of aquaculture at all levels.
As many wild fish stocks are already exploited at their maximum or have been overfished in Latin America, the significance and contribution of aquaculture will continue to grow. In order to fully realise this potentially valuable contribution to food security and economic growth, Latin America faces a number of challenges in the development and implementation of sound aquaculture governance through policy and planning. In some cases, aquaculture is considered an extension of fisheries, this being a failure to recognise that management strategies for fisheries and aquaculture are different. There is however, a recent recognition in the region of the imperative to create proper management and governance approaches to accommodate aquaculture’s circumstances and the need for governments and industry to work more closely together. Steps are being taken to address this; for instance, the FAOs Blue Growth Initiative for Latin America and the Caribbean has been initiated to improve sustainable management of aquaculture (and fishery) resources4.
National and provincial/state governments in both Canada and the US have strategies for the development of aquaculture, and governance systems are highly evolved. The thrust of aquaculture development in Canada is focused on environmental sustainability. In the US, development is also geared toward sustainability with offshore expansion.
With the notable exceptions of the major European aquaculture producers Norway, Russia and Turkey, the shaping of regulations and the instruments for development and investment in European aquaculture falls under the European Union (EU), and are highly evolved. The principal frameworks for EU aquaculture is the Common Fisheries Policy (CFP) as well as the EU Blue Growth Strategy, intended to stimulate and guide aquaculture development in Europe which is environmentally, socially and economically sustainable. In non-EU member states there are largely equivalent policies.
Although there has been criticism surrounding bivalve aquaculture (e.g. seabed deposition of solid wastes, changes to diversity, depletion of phytoplankton for other species, reduction of light reaching sea-bed), generally the impacts of scallop farming are seen as low and relatively benign7. There are in fact positive impacts and benefits that bivalve aquaculture can have on marine ecosystems8, 9.
Such positive natural or ‘ecosystem service’ aspect of bivalve aquaculture is increasingly being seen as a major factor to promote its growth. However ecosystem services from scallops does not feature strongly in the literature.
Feed is generally perceived to be one of the major risk factors in aquaculture production of fish and crustacea. However mussels consume food that occurs naturally in the environment and are not supplied with commercial aquafeeds; also they are not treated with chemicals or veterinary medicines unlike in other forms of aquaculture. Excluding seaweeds, one-third of all farmed seafood, some 20 million tonnes annually, is produced without additional feeding. The most important non-fed animal species, apart from bivalve molluscs (mainly clams, oysters, mussels and scallops), include two finfish species (silver carp and bighead carp), as well as other filter feeding animals such as sea squirts10.
Bivalve/scallop aquaculture is increasingly being seen the most environmentally sustainable type of seafood production10. As such increased scallop aquaculture is anticipated including the potential for increased production in the UK11. The Seafood 2040 Strategy for instance, highlights bivalve aquaculture as an opportunity to generate sustainable protein for domestic consumption or export, and provide employment in fragile coastal communities12. Increased UK scallop cultivation is likely to be driven by hatchery seed supply and the selling price of the product.
As bivalves are farmed in open marine environments, and because there are no available treatment or vaccination options, disease prevention is essential. Work continues to improve understanding of bivalve diseases and develop innovative solutions and tools for their management and prevention13, 14.
Scallops are a more sensitive species than others bivalves such as mussels and oysters in terms of their growing environment. Site selection for cultivating scallops is extremely important and factors include: substrate and/or depth of water; salinity; temperature; exposure to air, wind and currents; sedimentation rates; and food availability.
Buyers should seek assurances that all national and local laws are adhered to. All farms should have the required licences, permits and registrations in regards to their site and its operations accompanied by documentary evidence to demonstrate this compliance. Scallop operations may be managed to minimise site operations during peak sensitive periods or in times of low water quality episodes. Farm leases and permits can stipulate sustainable management practises.
In considering the environmental impacts of scallop aquaculture, it is important to view both the scale of the sector as well as the diversity of production systems1. The impacts of scallop aquaculture on the environment are often considered less than those of finfish and warm water prawn culture. Bivalves are considered keystone species in the ecosystem and therefore they can affect the surrounding environment in various ways2.
At all scales of bivalve production, the introduction the filtering bivalve molluscs and of physical on-growing structures to support them may produce changes in water movement and sediment dynamics that can affect both planktonic and seabed communities. However, the on-growing structures may also act as new habitat, and nursery areas for fish, crustaceans and molluscs3.
Operations associated with the growing and harvesting of scallops are relatively low impact in terms of activities that might lead to amenity and wildlife disturbance. One of the greatest potential impacts of cultivating filter feeders such as scallops is the net loss of energy (i.e. phytoplankton) from the ecosystem. Large monocultures, particularly in enclosed bays with limited water exchange, may exceed the carrying capacity (e.g. supplies of planktonic food) in that area and thus affect all aquatic organisms, including the farmed scallops themselves4, 5. Conversely, as scallops are primary consumers they can potentially mitigate impacts of nutrient enrichment (e.g. from land-based discharges and run-off), which can lead to eutrophication of coastal waters.
Coastal areas and estuaries where scallops are farmed are often sites of ecological and high amenity use, and therefore any large-scale cultivation may have impacts such as disturbing shore bird feeding sites, or on local navigation. Marine aquaculture operations may also have an aesthetic impact.
In many countries, siting a scallop farm would be restricted in areas with key biological or ecological functions. In the absence of such restrictions, the farmer should implement an environmental management plan to ensure no adverse effects on the ecological integrity of the area, and demonstrate there is no harm to threatened or endangered species and/or habitats. Best Management Plans (BMP’s), Codes of Good Practice6 often developed by industry groups, and certification are used as a means of preventing potentially unacceptable environmental interactions. Regarding the carrying capacity of the ecosystem and phytoplankton availability for other aquatic animals, farms should consider stocking appropriate densities.
Different countries regulate aquaculture and enforce policies differently, but often with the same goal of minimising environmental impact. Overall, the content of habitat regulations surrounding scallop culture takes into account environmental impacts and ecosystem services. Similarly, enforcement organisations should be identifiable, permitting and licensing process transparent and based on zoning or planning7 – although is not clear if such regulations in all locations are as effective or well-enforced8.
The consideration of water quality in scallop farming is important. As with other bivalves, scallops filter phytoplankton; they can also filter bacteria or viruses some of which can be a risk to human health and often derived from land-based activities such as water treatment, storm drainage and diffuse agricultural run-off. Bio-toxins may also be contained in seasonally occurring marine algae (Harmful Algal Blooms or HABs)1, 2 which the scallops can ingest.
Rigorous controls need to be in place in regards to harvesting shellfish such as mussels in order to protect consumers; ensuring that those sold into the supply chain meet strict food safety (health and hygiene) standards3. The UN Food and Agriculture Organisation (FAO) has developed the Codex Alimentarius or “Food Code” which is a set of voluntary standards, codes of practice and guidelines covering food and its production, including those for bivalve molluscs4, 5, and specifically scallops6 . The aim of the Codex is to protect public health and to support balanced trade relationships in food, and all World Trade Organisation (WTO) signatories are obliged to observe them. In practice, most countries have laws that are very broadly equivalent to Codex guidelines but differ from them in the detail.
European Hygiene Regulations7 state that shellfish business operators are responsible in ensuring that bivalve molluscs meet strict standards. The UK Food Standards Agency, in compliance with European regulations, has classified shellfish harvesting areas and beds on the basis of the level of the bacterium E.coli in mollusc flesh. Depending on shellfish production area classification (A, B or C) certain procedures must be followed to enable harvested mussels to enter the market. Molluscs harvested from Class A areas can go straight to market, but they are often purified (depurated) to provide additional assurance of quality; those harvested from Class B areas must be purified before being sold to consumers. All molluscs sold on the UK market must contain less than 230 cfu (colony forming units) of E.coli per 100 g of flesh8, 9.
Depuration is a technique whereby live shellfish and bivalves such as mussels and oysters are placed in systems with continually circulated and sterilised seawater in order to remove undesirable substances, pollutants, parasites or organisms of possible harm to human beings (e.g. pathogenic bacteria)10. Depuration however is not a method widely used for scallops; shucking is. Shucking involves the removal of all the viscera from the scallop to leave only the edible parts, and this removes the vast majority of bacteria and viruses, as well as algal bio-toxins the scallop may have ingested11. As scallops are not eaten raw (unlike other shellfish such as oysters), appropriate cooking also eliminates these risks, as well as those potentially posed by norovirus12. End product testing of live shellfish is also undertaken in countries such as the UK, to ensure shellfish products that enter the market are safe to eat13, 14.
For many reasons, there is an on-going societal need to reduce coastal water pollution, and this is of particular importance to protect and enable the growth of bivalve aquaculture. Legislation exists to control water pollution, for instance that in the UK15, but pollution incidents do occur, and efforts continue to improve water quality16, 17.
Active management (i.e. continuous, real time decision making, taking account of all the available information enabling shellfish producers to decide what action to take in regards to when and where to harvest), is an important tool to reduce the risks from poor water quality and HAB episodes18, especially in inshore waters.
Most global scallop aquaculture does not rely on hatchery seed but on wild spat collection and this should be from abundant, well-regulated natural sources. In countries where natural spatfall is poor, or in the case of introduced scallops, spat can be hatchery reared. Hatchery produced spat is increasing being seen as a way to reliably secure quality seed for on-growing.
As many farmed scallops are cultured in their native ranges and are wild-caught or one generation hatchery-raised, there is little evidence to support negative effects on ecosystems or wild populations1. In the early development of scallop farming non-native scallops were introduced to some producer countries, for instance the Bay scallop (native to the Americas) was intentionally introduced to Asia, however no effects on ecosystems or native species have been reported1. It is likely that further non-native species will be trailed and grown in countries outside their native range2.
The movement of scallop seed, stock and equipment could potentially introduce or transfer diseases and pests which can affect farmed scallops or native scallop species4, 5, and high-density cultivation can promote the incidence and spread of parasites and disease6.
The introduction of non-native bivalve species for aquaculture purposes is now highly regulated helping to reduce the introduction of diseases and pests. Internationally the “Code of Practice on the Introductions and Transfers of Marine Organisms 2005”7 has been adopted by many countries, whilst in the EU international shellfish trade has been regulated for many years8. Upcoming European legislation will further prioritise the prevention and control of biological invasions9.
Biosecurity measures are important to mitigate diseases that can affect scallops10. Key elements of biosecurity include; practical and appropriate legislative controls, adequate diagnostic and detection methods for infectious diseases, disinfection and pathogen eradication methods, reliable high quality sources of stock, and best management practices11, 12 Preventive regulatory measures aim to limit imports only from countries where no outbreak of disease occurs13. It is also critical that scallop hatcheries implement strict biosecurity plans to help prevent transfer of disease into, within and from their facilities.
Transfers of spat from hatcheries to on-growing areas, or the relaying of bivalves between sites must be carried out in ways that minimise the risk of disease transfer10, and the monitoring of scallop populations as well as parasite occurrence/levels is important. Management measures include regulation (e.g. lease conditions and permit requirements) but also the use of voluntary agreements, Codes of Good Practice and certification.
Also important are designations to protect sensitive marine habitats. For example in the UK these include Marine Protected Areas (MPAs), Special Areas of Conservation (SACs), Special Protected Areas (SPAs), and intertidal areas identified as Sites of Special Scientific Interest (SSSIs)14.
Aquaculture (and fisheries) certification and labelling programmes have become a primary tool to address sustainability issues of farmed seafood, and the development of third party assessment and certification has provided new forms of governance traditionally dominated by state-based regulation1, 2. The growth in the number of certification schemes has led to confusion surrounding the myriad of them out there. To try and combat this, the Global Sustainable Seafood Initiative (GSSI)1 has developed its global benchmarking tool to measure and compare certification schemes and standards performance across seafood production.
Given the prominence of environmental issues as the driver for the development of aquaculture standards, there is an understandably strong emphasis on environmental criteria within them3. Certification enables aquaculture producers to voluntarily demonstrate their responsible farming practices by: complying with national legislation; minimising impact on habitats and wildlife; making the best use of locally available resources; and ensuring the best use of feed and therapeutic products.
Aquaculture certification currently has moderate to high coverage of labour standards (e.g. minimum wage)3, however, increased social and economic requirements related to human rights, gender and sustainable livelihoods are being developed.
Since 2011, a partnership of UK businesses called the Sustainable Seafood Coalition (SSC)4 have been working to ensure all fish and seafood sold in the UK comes from sustainable sources, and aquaculture certification plays a pivotal role. All members need to ensure that the aquaculture source (considering feed mills, hatcheries, and farm sites) is certified under a third party standard, or audited to a members own good aquaculture standard or code of practice5.
The table below looks at some of the major aquaculture certification schemes, including those for bivalves, and if they address the Key Considerations highlighted throughout the profiles. It also highlights which scheme has a standard/s successfully benchmarked by the Global Sustainable Seafood Initiative (GSSI)1.
Read more on aquaculture certification, including that of scallops, after the table.
|Certification Scheme: Description and Links||Governance||Farm Siting||Nutrient Pollution||Feed||Disease, Medicines & Chemicals||Escapes & Introductions||Wild Seed||GSSI Benchmarked|
Founded in 2010 by WWF and IDH (Dutch Sustainable Trade Initiative) the ASC is an independent not for profit organisation with global influence. ASC aims to be the world’s leading certification and labelling programme for responsibly farmed seafood.
The ASC consumer label demonstrates the integrity of the seafood product.
GAA BAP has been certifying aquaculture since 2004, and is administered by the GAA, a nonprofit organization dedicated to advocacy, education and leadership in responsible aquaculture. Aquaculture Facility Certification:
The BAP program employs a star system to signify the integration levels of BAP certification along the aquaculture production chain. These stars are displayed on the BAP logo and appear on packaging for a variety of farmed seafood products worldwide.
GG offers 16 standards for 3 scopes: Crops, Livestock, and Aquaculture. GG has been one of the most widely accepted private sector food safety certification in the world since 2007.
GG Aquaculture certified producers have now the option to use the consumer facing GGN Certified Aquaculture label.
Friend of the Sea (FoS)
FoS is a non-profit NGO, whose mission is the conservation of the marine habitat. FoS is now a leading international certification project for products originated from both sustainable fisheries and aquaculture:
All aquaculture products sold as “organic” in the European Union (EU) have to fulfil the requirements that are laid down by the EU regulations:
This includes products certified according to private organic standards. The EU Organic logo makes organic products easily identifiable by consumers.
Naturland was founded in 1982 when organic agriculture was regarded as a marginal issue. Since the mid-1990s, Naturland has developed standards for different species and production systems in aquaculture:
The Naturland label is intended as a guide for consumers.
The Soil Association was formed in 1946 and champions organic principles and practice.
The Soil Association logo sends a message to consumers that the product is organically produced.
• – Indicates the Certification Scheme addresses the Key Consideration
✔ – Indicates the Certification Scheme has had one or more of its Standards benchmarked against the Global Benchmark Tool Version 1 and recognised by the GSSI Steering Board
Certified Aquaculture Production
Production of certified seafood, both aquaculture and wild catch, has grown rapidly over the past decade and now represents a significant portion of global seafood production. Certified sustainable seafood in 2003 equated to some 500,000 tonnes (0.5% of global production); in 2015 this figure had risen to 23 million tonnes (14% of global production). Some 80% of certified seafood is wild catch, but certified aquaculture is growing twice as fast and is set to dominate growth in certified seafood for the foreseeable future3.
In 2015, certified aquaculture accounted for 6.3% of world aquaculture production. Of this 6.3%, seven species groups were dominant (i.e. salmon, pangasius, mussels, tilapia, prawns, trout and sea bream) and accounted for 97%3. This relatively low global level of certified aquaculture and the narrow range of species groups, is largely due to:
Certification of small-scale aquaculture continues to be an issue, mainly due to the cost and difficulties in complying with standards; key challenges include finance, technical knowledge and organisational capacity. Educating small-scale farmers on how to comply, as well as identifying national policy and regulatory gaps supporting small-scale aquaculture certification, is becoming ever more necessary6. Multiple-farm or ‘cluster’ certification may be a way forward for small-scale producers.
Four schemes are responsible for the majority of certified aquaculture production, namely the Aquaculture Stewardship Council (ASC), Global Aquaculture Alliance Best Aquaculture Practice (GAA BAP), GlobalG.A.P. (GG) , and Friend of the Sea (FoS)3.
Certified Scallop Production
In 2015, farmed bivalves accounted for 8% of certified aquaculture globally3.
Figures provided by the certification schemes themselves and relating to their totals of certified farmed scallops/bivalves break down into:
(It is important to note that certification under one scheme does not preclude certification under another, and gathering accurate data on rates of multiple certification is very difficult. As a result simply adding the production volumes of individual schemes can result in double counting and overestimation. The authors of the aggregate data referred to above make no adjustment for multiple certification.)