What’s the challenge?

A growing population is putting increasing pressure on fish stocks. The United Nations estimates that 87% of world fish stocks are fully exploited or overfished and require precautionary management. How can we avoid the collapse of a resource that remains an essential part of food security and vital to the communities and livelihoods of half a billion people across the planet?


  • Fish is one of the most-traded food commodities, worth £63bn in 2008.
  • Oceans represent the planet’s largest habitat and support the life of nearly 50% of all species on the planet
  • Every year almost 100 million metric tons of fish and shellfish are caught and eaten. That is three times the weight of every man, woman and child in USA.
  • Globally, fish provides about three billion people with almost 20% of their intake of animal protein, and 4.3 billion people with about 15% of such protein.
  • In 2011 a UN report showed that global fish consumption had hit a record high of 17kg per person.
  • China has been accountable for the majority of the increase in world per capita fish consumption, owing to the substantial increase in its fish production, particularly from aquaculture. China’s share in world fish production grew from 7% in 1961 to 35% in 2010.

Source:  UNFAO: The State of World Fisheries and Aquaculture



Fish farming and aquaculture

Around the world, over 100 different fish and shellfish species are farmed, and aquacultural practices vary significantly in terms of scale, methods and impact. Fish are farmed in everything from simple ponds to high-tech electronically controlled tanks.

Inland and marine aquaculture production has been growing at an unprecedented rate. One third of fish is derived from aquaculture. Fish farming,  the main form of aquaculture, is the process of raising fish commercially in tanks or enclosures, usually for food supply. With the ever increasing global demand for food, and widespread over-fishing of wild fisheries, fish farms offer a reliable food supply for millions. But what are the costs? In the next decade, the majority of fish we consume will be farmed, rather than wild.

Fish farms, with careful management, can be sustainable. However, their impacts on surrounding environments can be damaging. In order to be sustainable, fish farms must minimise their impact, by treating wastewater, containing stocks, preventing the spread of diseases and not removing fish, particularly juveniles, from wild fisheries. The economic sustainability of aquaculture must also be considered. Fish farming creates many jobs globally, and farmed fish is a valuable commodity traded on the world market.

Fish farming methods

  • Bags/Racks – Juvenile shellfish are cultivated in bags on racks above the seabed. Most cultivated shellfish filter-feed, so there is no need for fish feed.
  • Hatchery – Fish are bred and reared in nurseries either for use in aquaculture or to be released as wild fisheries.
  • Open net pens or cages – used to enclose fish in offshore coastal areas or in freshwater lakes. This is considered a high-impact aquaculture method, due to the waste which passes freely from the fish farm to surrounding waters, the ability of farmed fish to escape and compete or breed with wild fish, and the spread of diseases and parasites to wild fisheries.
  • Ponds – Fish are enclosed in an artificial or natural body of fresh or salt water. This allows waste water to be contained and treated. However, untreated wastewater discharge can cause significant environmental impacts in the surrounding area.
  • Raceways – Fish farmers divert water from a waterway so that is flows through channels containing fish. If untreated, wastewater from raceways can contaminate waterways and spread disease; escaped fish are another problem.
  • Recirculating systems – Fish are raised in controlled tanks in which water is treated and recycled. Fish cannot escape and wastewater is treated. However this aquaculture method is costly and required a power supply.
  • Tuna ranching – Valuable juvenile species, usually carnivorous top predators, are captured from the wild and grown to harvest size in farms. Highly profitable species such as bluefin tuna are caught at a relatively large size and grown before harvesting. The high use of feed and the release of waste causes a negative impact on the environment, while removing juveniles from the wild can damage and imbalance natural ecosystems.

Bycatch and habitat loss

Bycatch is the unintentional catch of fish, birds, turtles and mammals in fishing nets. Habitat destruction from trawling at the bottom of the oceans disturbs an area of the seabed as large as Brazil, the Congo and India combined every year. Changes to the climate are also altering fish migrations and supply.

Food chains

The overfishing of a particular species does not just damage the population of that fish alone. It can have serious effects further up the food chain. For example, Herring is a vital prey species for cod. Therefore, when Herring are overfished the cod population suffers as well. Since the early 1980s, six countries, including Japan and the former USSR have been harvesting krill, which is the main food for the great whales, and which also supplements the diets of seals, penguins, squid and fish.



Wealthy nations once obtained most of their fish by fishing themselves. Today there are more likely to buy and import it than catch it. Japan buys more than twice as much fish as it catches, while Peruvians, the number two seafood producers in the world, consume barely any at all.

Case study: Peru
In Peru, a small fish called the anchoveta was caught in huge numbers to be made into fish meal for animals. In 1970, more than 69,000 tonnes were caught, making it the biggest fishery in the world. One thousand five hundred boats were catching 100,000 tonnes of anchoveta every day. By 1972, the daily yield had risen to 180,000 tonnes.

he fishermen ignored warnings from the United Nations Food and Agriculture Organisation that their catches were too big, and when a natural upwelling of warm water entered the normally cool, nutrient-rich waters the anchoveta inhabited, this, combined with a lack of breeding stock in the population was enough to cause the total collapse of the anchoveta fishing industry.

Panel discussion

21st Century Challenges held a panel discussion on 10 October 2012 to discuss the issue.

Paul Rose, presenter
Paul is Vice President of the Royal Geographical Society (with IBG) and Chair of the Expeditions and Fieldwork Division.  He is an expert polar, environmental, exploration and field science consultant.

His recent BBC documentaries have included Oceans: Exploring the secrets of our underwater world and Frank Wild: Antarctica’s Forgotten Hero. He presented the BBC Human Planet Proms at the Royal Albert Hall. Paul has also presented Britain’s Secret Seas, Voyages of Discovery, Take One Museum, Meltdown and Wind.
Paul’s voice-over work includes making the official recording of Captain Scott’s diaries for the British Library.
He reports for BBC News and makes live appearances on BBC Breakfast, BBC 24 News, Sky News and local TV News.

He was the Base Commander of Rothera Research Station, Antarctica for the British Antarctic Survey for 10 years and was awarded HM The Queen’s Polar Medal. For his work with NASA and the Mars Lander project on Mt Erebus, Antarctica he was awarded the US Polar Medal. The Royal Geographical Society (with IBG) presented The Ness Award to Paul – “For the popularisation of Geography and the wider understanding of our world”. Paul has a mountain named after him in Antarctica and is an Honorary Fellow of the University of Cumbria.

Frank Pope, Ocean Correspondent, The Times
Frank is currently the Ocean Correspondent for The Times: the world’s only national newspaper with a reporter dedicated to covering the 71 per cent of the planet that is covered by water. The beat is as wide as the horizon and as deep as the Mariana Trench, covering everything from offshore energy to environment, piracy to science, shipwrecks and exploration.

Before working for The Times, Frank worked in marine archaeology, examining & excavating shipwrecks around the world. One project – the excavation of an Asian junk sunk in deep water off Vietnam – was the subject of his first book, Dragon Sea: A True Tale of Intrigue, Treasure and Adventure Under the Waves.

In March 2012 his second book, 72 Hours was released, exploring the extraordinary story of the Royal Navy submarine rescue team and their dramatic last mission to save the crew of a trapped Russian submersible.

He has filmed a couple of ocean-related series for the BBC, including the two-part BBC2 series on the forgotten shipwrecks of the river Thames, and in 2011 BBC’s Britain’s Secret Seas. Frank is a regular speaker at schools and other events on this subject, and is an Ambassador for the Blue Marine Foundation. Twitter @Papa_Franco

Dr David Agnew, Director of Standards at the Marine Stewardship Council
Dr David Agnew is Director of Standards at the Marine Stewardship Council and an acknowledged world expert on Antarctic fisheries and Illegal, Unreported and Unregulated fishing. His global experience includes Europe, Africa, South America, North America, Australasia and all oceans.

Previously David was Fisheries Director of the fisheries consultancy MRAG Ltd. He is also Honorary Senior Research Fellow in Fisheries and Population Biology at Imperial College London, is Chairman of Scientific Committee of CCAMLR, is a past chairman of the Technical Advisory Board of the MSC and a past member of the Board of Trustees of the MSC.

He holds a PhD in marine biology from the University of Glasgow, UK and is an experienced stock assessment scientist and modeller, having conducted research on a wide range of that and other fisheries management topics, including ecosystem based fisheries management and global fisheries governance. He has managed small and large projects for diverse clients such as the European Commission, World Bank, Forum Fisheries Agency and UK government departments. He was Principal Scientific Advisor the UK Government on fisheries science and management of its overseas territories, particularly in the South Atlantic and Antarctic. From 1989 to 1996 he was Data Manager with CCAMLR in Hobart, Australia. He has published more than 200 papers and reports.

Dr Heather Koldeway, Head of Global Programmes, Zoological Society of London (ZSL)
Heather is Head of Global Programmes, Zoological Society of London (ZSL). In 1997, Heather became the Curator of the Aquarium and Reptile House at London Zoo. Since starting at the Zoological Society of London, Heather has worked to advance the role of aquariums in fish conservation globally.

In 1998, she facilitated a series of workshops that established the first coordinated conservation breeding programmes for fish and aquatic invertebrates in European aquariums. She has co-chaired this initiative since its inception and was recently appointed as the Aquarium Committee Chair for the World Association for Zoos and Aquariums following her role in developing the global aquarium conservation strategy.

One of Heather’s most rewarding moments was being involved in the designation of the world’s largest Marine Protected Area in the Chagos/British Indian Ocean Territory and she continues a role in developing a research strategy for the region. She retains an active engagement in research, supervising PhD students (working in the Philippines, Portugal and Sri Lanka), publishing papers and was recently appointed an Adjunct Professor at the Fisheries Centre, University of British Columbia, Canada.

Heather is an Ambassador of the Blue Marine Foundation, which exists to fix the largest solvable problem on the planet – the crisis in the oceans, with a diverse network of passionate and influential individuals, dedicated to solving the marine crisis.

Heather was appointed an Adjunct Professor at the Fisheries Centre, University of British Columbia, Canada in 2010. She is a Board member of the Chagos Conservation Trust, Shark Trust and Project Seahorse Foundation for Marine Conservation, Philippines, as well as representing ZSL on a number of national and international conservation committees.

”Right now we are looking at 1000 time higher extinction rates that from what we know from the fossil records” Dr Heather Koldewey, ZSL

”We are losing species at an abnormal rate, due to one species, and that’s us” Dr Heather Koldewey, ZSL

Further reading

Overfishing, Liam Carr, US National Oceanic and Atmospheric Administration for ‘Ask the experts’, http://www.rgs.org

China’s unsustainable fish farms, Geographical Magazine, 23 January 2015

New perspectives on an aquacultural geography, Geography Directions, November 2013