Why is "Assuming all aquaculture is environmentally sustainable." a common mistake in Marine Aquaculture?

Why it happens: Students are told aquaculture reduces pressure on wild fish and assume it has no environmental cost. How to avoid it: The environmental impact varies dramatically by species and method. Salmon and shrimp farming causes serious pollution and habitat destruction. Shellfish farming is sustainable. Always specify the type of aquaculture when discussing impacts.

Why is "Not mentioning mangrove destruction when discussing shrimp farming impacts." a common mistake in Marine Aquaculture?

Why it happens: Students focus on water pollution and disease but overlook habitat impacts. How to avoid it: Mangrove destruction for shrimp ponds is the most high-profile negative impact of aquaculture in the Cambridge syllabus. It appears in mark schemes regularly. Always include it for shrimp/prawn farming examples. Source: 0680 Mark Schemes 2022-2024 — mangrove destruction awarded dedicated marks.

Why is "Saying aquaculture has completely solved overfishing." a common mistake in Marine Aquaculture?

Why it happens: Students hear aquaculture is the solution to wild fish declines and take this too literally. How to avoid it: Aquaculture currently supplies over 50% of seafood but does NOT eliminate wild fish pressure — in fact, some aquaculture (salmon farming) still requires large quantities of wild-caught fish for feed. It is a partial solution, not a complete one.

WaterCambridge IGCSE Environmental Management (0680)

Marine Aquaculture

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Marine Aquaculture — Cambridge IGCSE Environmental Management 0680

Aquaculture (fish farming) is the fastest-growing food production sector, now supplying over half of global seafood. This subtopic covers methods, benefits and environmental impacts of marine and coastal aquaculture.

What you’ll learn

Mapped to the Cambridge IGCSE 0680 syllabus (2027-2029).

3.4a — Describe methods of marine aquaculture.
3.4b — Evaluate the benefits and environmental impacts of marine aquaculture.
3.4c — Describe strategies for more sustainable aquaculture management.

Methods of Marine Aquaculture

Sea cages, shellfish culture and land-based systems are the main approaches.

Open-water sea cage farming:

Fish are raised in floating net cages anchored in sheltered bays or offshore.
Common species: salmon (Norway, Scotland, Chile), sea bass, sea bream, tuna.
Cages allow water circulation but fish are confined.
Feed is added artificially (pellets made from fishmeal, soy, additives).
Advantages: low land cost; easy access to sea.
Disadvantages: waste accumulates on seabed below; disease spreads easily; escapees.

Shellfish culture (bivalves):

Mussels, oysters, clams, and scallops are farmed on ropes, rafts, longlines or on the seabed.
Unlike finfish, shellfish are filter feeders — they feed on naturally occurring phytoplankton.
Do not need additional feed input — very efficient and sustainable.
Absorb and store carbon; filter water, improving local water quality.
Advantages: low environmental impact; can restore degraded coastal ecosystems.

Seaweed farming:

Seaweeds grown on ropes or rafts in coastal waters.
Uses no freshwater, no fertiliser, no feed — entirely natural nutrition from seawater.
Products: food (nori, agar), animal feed, biofuel, bioplastics.
Very sustainable; seaweed absorbs CO₂ and nutrients from the water.

Land-based recirculating aquaculture systems (RAS):

Fish raised in tanks on land, with water continuously filtered and recirculated.
Very little water exchange with natural environment → minimal pollution of waterways.
Can be located anywhere — not dependent on coastal access.
High energy costs for pumping and filtering.
Allows production of species in areas far from their natural range.

Shrimp farming (pond culture):

Coastal ponds constructed for intensive shrimp production.
Common in Thailand, Vietnam, Ecuador, Bangladesh.
High economic value but major environmental consequences (see below).

Sea cages and shrimp ponds dump waste into coastal water; shellfish and seaweed longlines actually clean it — sustainability varies enormously by method.

Sea cages: salmon, sea bass in net pens — waste on seabed; disease risk.
Shellfish (mussels, oysters): filter feeders; no added feed; filter water — very sustainable.
Seaweed: no feed, no water, absorbs CO₂ — most sustainable form.
RAS (land-based tanks): minimal pollution; high energy cost.
Shrimp ponds: high value; major environmental impact in SE Asia.

Benefits of Marine Aquaculture

Aquaculture relieves pressure on wild stocks, provides food and supports coastal livelihoods.

Reducing pressure on wild fish stocks:

Global wild fish catches have been roughly flat since the 1990s — many stocks are overfished.
Aquaculture provides additional seafood without further depleting wild populations.
For some species (e.g. tilapia, pangasius, mussels, oysters), aquaculture has almost entirely replaced wild capture fisheries.

Food security:

Provides reliable, year-round supply of protein-rich food — not dependent on variable wild catches.
Fish and shellfish are particularly important protein sources in Southeast Asia, West Africa, and Pacific Island nations.
Aquaculture grows faster than any other food sector — growing to feed a population expected to reach 10 billion by 2050.

Economic development:

Employment in farming, processing, packaging, transport, equipment supply.
In Norway, salmon aquaculture is one of the country's largest export industries.
In Southeast Asia, shrimp and fish farming provides livelihoods for millions of small-scale farmers.

Efficient food production:

Fish convert feed to protein more efficiently than land animals:
- Fish: ~1.2 kg feed per kg of body weight gained (Feed Conversion Ratio, FCR ≈ 1.2).
- Chicken: ~2 kg feed per kg.
- Pig: ~3 kg feed per kg.
- Beef cattle: ~7–8 kg feed per kg.
Lower land and water footprint than terrestrial meat production.

Carbon footprint:

Shellfish and seaweed farming have among the lowest carbon footprints of any protein source.
Salmon farming has lower emissions per kg protein than chicken or pork in some studies.

Reduces pressure on wild fish stocks — some stocks would collapse without aquaculture.
Food security: reliable year-round protein supply.
FCR (Feed Conversion Ratio): fish ~1.2; chicken ~2; pig ~3; cattle ~7–8.
Employment and export revenue in coastal communities.
Shellfish and seaweed: lowest carbon footprint of any farmed protein.

Environmental Impacts of Aquaculture

Water pollution, disease, genetic pollution from escapees and habitat destruction are the main problems.

Water pollution (sea cages and shrimp ponds):

Fish waste (faeces, uneaten feed) falls through net cage floors to accumulate on the seabed below.
Causes localised eutrophication and oxygen depletion.
Sediment beneath cages becomes anaerobic (black, foul-smelling) — no organisms can survive.
Shrimp ponds discharge waste water directly into coastal waters.

Chemicals and antibiotics:

Antibiotics used to prevent and treat bacterial diseases in intensive sea cages.
Antibiotic residues enter marine environment → contribute to antibiotic resistance in bacteria.
Pesticides (e.g. emamectin benzoate) used against sea lice — toxic to non-target crustaceans.
Anti-fouling chemicals applied to nets — toxic to marine invertebrates.

Disease and sea lice:

High-density fish populations in cages are ideal for disease and parasite spread.
Sea lice (Lepeophtheirus salmonis) infest farmed salmon; larvae spread to infect wild salmon swimming past cage sites.
Has contributed to population decline of wild Atlantic salmon near fish farm sites.

Genetic pollution from escapees:

Farmed salmon (selectively bred for rapid growth) escape through storms or net failures.
Interbreeding with wild salmon alters the genetic diversity of wild populations — wild fish become less adapted to local conditions.
Farmed fish have lower survival rates in the wild — competition with better-adapted wild fish.

Habitat destruction — mangroves:

Shrimp farming in Thailand, Vietnam, Ecuador, Bangladesh has destroyed vast areas of mangrove forest.
Mangroves are highly biodiverse coastal habitats: nursery grounds for fish; protect coasts from storms and erosion; store large amounts of carbon (blue carbon).
Estimated 20–35% of world's mangroves destroyed for aquaculture (mainly shrimp farming).
Abandoned shrimp ponds leave behind degraded, salinised land that cannot be restored easily.

Feed ingredients:

Carnivorous fish (salmon, tuna) require high-protein feed often made from wild-caught small fish (anchovies, sardines, sand eels).
Every 5 kg of wild fish converted into fishmeal produces ~1 kg of farmed salmon.
Net protein loss — reduces overall seafood availability.
Shift to plant-based (soy) and insect meal feeds being researched to reduce this impact.

Sea cage waste → eutrophication and anaerobic seabed below cages.
Sea lice from cages spread to wild salmon — contributing to wild population decline.
Escaped farmed salmon → genetic pollution of wild populations.
Shrimp farming: 20–35% of mangroves globally destroyed.
Salmon feed: 5 kg wild fish → 1 kg farmed salmon (net protein loss).

Towards More Sustainable Aquaculture

Improved management, certification, and alternative feeds can reduce aquaculture's environmental footprint.

Integrated Multi-Trophic Aquaculture (IMTA):

Combine species from different trophic levels in the same area.
Example: salmon (primary species) + mussels (filter uneaten feed and waste) + seaweed (absorbs dissolved nutrients).
Waste from one species becomes food for another — reducing overall pollution.

Certification schemes:

Aquaculture Stewardship Council (ASC): Sets standards for responsible farming — covering pollution, disease management, feed sourcing, social responsibility.
Consumers can choose ASC-certified seafood to support better practices.
Best Aquaculture Practices (BAP): Similar US-based certification.

Alternative feeds:

Replace fishmeal with insect meal (black soldier fly larvae), algae, single-cell proteins, soy.
Research into using food waste and organic by-products as feed.
Reduces dependency on wild fish for feed.

Recirculating Aquaculture Systems (RAS):

Zero-discharge land-based systems — no pollution of waterways.
Water is treated and reused; fish cannot escape; disease controlled.
High energy cost is the main challenge.

Offshore farming:

Moving sea cages to deeper, more exposed offshore locations.
Stronger currents disperse waste; less impact on local ecosystems.
Technical challenge: withstand storms; more difficult to manage.

Mangrove restoration:

International and national programmes to restore mangroves where shrimp ponds are abandoned.
Some shrimp farming certified as 'mangrove-friendly' with smaller ponds and maintenance of mangrove corridors.

IMTA: salmon + mussels + seaweed — waste from one feeds another.
ASC certification: responsible farming standards; consumers can choose certified seafood.
Alternative feeds: insect meal, algae — reduces wild fish demand.
RAS (land-based): zero discharge; high energy cost.
Offshore cages: better dispersal; harder to manage.

Sources: Cambridge IGCSE Environmental Management 0680 syllabus 2027-2029, Section 3.4; FAO The State of World Fisheries and Aquaculture 2024; 0680/12 May/Jun 2023 — Q13 (marine aquaculture); WWF — Aquaculture: Finding Sustainable Solutions. Last reviewed 2026-05-15.

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Step-by-step worked examples — Marine Aquaculture

Step-by-step solutions to past-paper-style questions on marine aquaculture, written exactly the way a tutor would explain them at the board.

1Describe what marine aquaculture is and how it works
Core• definition, process, aquaculture
Question
Describe what marine aquaculture (fish farming) is and outline the methods used to raise marine species commercially.
Step-by-step solution
1. Step 1
  Marine aquaculture is the controlled breeding, rearing and harvesting of fish, shellfish, seaweed and other marine organisms for commercial food production. It is the aquatic equivalent of farming on land.
2. Step 2
  Sea cages / net pens — large mesh cages anchored offshore allow fish (e.g. salmon, sea bass, sea bream) to be raised at high density in open seawater. Fish are fed commercial pellets; waste falls through the cage bottom to the seabed.
3. Step 3
  Pond and tank systems — used in shallow coastal areas or inland facilities. Shrimp, tilapia, and catfish are commonly farmed in artificial ponds. Water quality (oxygen, temperature, pH) is monitored and controlled.
4. Step 4
  Shellfish (bivalve) farming — mussels, oysters and clams are suspended on ropes or raised on the seabed. They filter-feed naturally on phytoplankton, requiring no artificial feed. This makes bivalve aquaculture one of the most sustainable food production methods.
Answer
Aquaculture = controlled rearing of marine species. Methods: sea cages (salmon, high density), pond/tank systems (shrimp, tilapia), shellfish farming on ropes (filter-feeding, no artificial feed — most sustainable).
Examiner tip
Shellfish/bivalve farming is consistently identified as environmentally superior — no artificial feed, naturally cleans water, can restore reef habitats. Know this contrast with intensive fish cages.
2Benefits of aquaculture for food security
Core• benefits, food security
Question
Give THREE benefits of marine aquaculture for food security and the economy.
Step-by-step solution
1. Step 1
  Reduces pressure on wild fish stocks — aquaculture provides an alternative protein source, reducing demand for wild-caught fish. This gives overexploited wild fisheries time to recover, helping to preserve biodiversity and long-term food supply.
2. Step 2
  Reliable food supply — unlike wild fishing (which is affected by seasonal variation, weather, and stock fluctuations), farmed fish can be produced year-round in controlled conditions, providing a consistent protein supply for local and export markets.
3. Step 3
  Economic development and employment — aquaculture provides jobs in coastal communities (feeding, maintenance, harvesting, processing) and generates export income. In Norway, salmon aquaculture is a multi-billion dollar export industry; in Vietnam, shrimp farming supports millions of rural households.
Answer
Reduces wild fishery pressure, provides reliable year-round food supply, and creates coastal employment and export income. Aquaculture now supplies >50% of global seafood demand.
Examiner tip
The statistic that aquaculture now supplies more than half of all seafood consumed globally is relevant context — it illustrates the scale and importance of the industry.
3Evaluate the environmental impacts of marine aquaculture
Extended• Adapted from 0680/22 Oct/Nov 2023• evaluate, environmental impacts
Question
Evaluate the environmental impacts of marine aquaculture. Include both positive and negative effects in your answer.
Step-by-step solution
1. Step 1
  Negative — water pollution: high-density fish cages produce large quantities of faeces, uneaten feed and antibiotics/chemicals that fall to the seabed or disperse in surrounding water. This causes localised eutrophication (oxygen depletion, algal growth), smothers benthic (bottom-dwelling) organisms, and can spread harmful chemicals to wild species.
2. Step 2
  Negative — disease and parasite spread: dense fish populations are ideal breeding grounds for parasites (sea lice are a major problem in salmon farming) and bacterial diseases. Parasites and diseases spread from farmed to wild fish, threatening wild populations. Sea lice from salmon farms have devastated wild sea trout populations in some regions.
3. Step 3
  Negative — habitat destruction: mangrove forests in Southeast Asia (Thailand, Vietnam, Indonesia) have been cleared extensively to create shrimp ponds. Mangroves are nursery habitats for wild fish, coastal protection against storms, and major carbon stores — their loss is ecologically devastating.
4. Step 4
  Negative — use of wild fish for feed: carnivorous farmed fish (salmon, sea bass) are fed fishmeal and fish oil produced from wild-caught small fish (anchovies, herring, sardines). This shifts fishing pressure to lower food-chain species, which are vital food sources for marine mammals and seabirds.
5. Step 5
  Positive — shellfish farming: mussel and oyster farming adds no artificial feed to the system, can improve local water quality by filtering phytoplankton and suspended particles, and provides structural habitat for other marine species. It is genuinely low-impact aquaculture.
6. Step 6
  Conclusion: the environmental impact of aquaculture depends heavily on species and method. Intensive salmon and shrimp farming causes serious pollution, disease and habitat problems. Shellfish farming is far more sustainable. Stronger regulation, site selection guidelines, and investment in plant-based fish feeds can reduce the sector's footprint significantly.
Answer
Negatives: water/seabed pollution, disease spread to wild fish, mangrove destruction (shrimp farms), wild fish needed for feed. Positive: shellfish farming is low-impact, filters water. Conclusion: impact varies by species/method; regulation needed.
Examiner tip
Mangrove destruction for shrimp aquaculture is the single most commonly tested environmental impact of aquaculture in 0680 papers. Always mention it in evaluate answers. Equally, always mention shellfish farming as the sustainable contrast.
4Evaluate the trade-off between shrimp farming and mangrove conservation in Southeast Asia
Extended• Adapted from 0680/12 Oct/Nov 2024• mangroves, shrimp farming, Southeast Asia, trade-off
Question
Between 1980 and 2005, approximately 35% of global mangrove forests were cleared, much of it to create shrimp ponds in Southeast Asia. (a) Explain the ecological services provided by mangroves that are lost when they are cleared. (b) Evaluate the economic argument for and against clearing mangroves for shrimp aquaculture. (c) Suggest and justify ONE policy that governments in the region could implement.
Step-by-step solution
1. Step 1
  Ecological services provided by mangroves: (1) Nursery habitat: mangrove root systems provide sheltered, food-rich habitat where juvenile fish, shrimps and crabs develop before migrating to open water. An estimated 75% of commercial fish species spend part of their lifecycle in mangrove nurseries — destroying mangroves reduces wild fish and shrimp stocks. (2) Coastal protection: mangroves dissipate wave energy and reduce storm surge impact on coastal communities. The 2004 Indian Ocean tsunami caused significantly less coastal damage in areas with intact mangroves than in cleared areas — an ecosystem service worth billions in avoided infrastructure damage. (3) Carbon sequestration (blue carbon): mangroves store up to 10 times more carbon per hectare than terrestrial forests, primarily in waterlogged soils. Clearing mangroves releases this stored carbon as CO₂, contributing to climate change. (4) Water filtration: mangroves filter agricultural runoff and sediment, maintaining water quality in coastal bays — improving conditions for coral reefs and seagrass beds adjacent to mangrove systems.
2. Step 2
  Economic argument FOR clearing mangroves: Shrimp farming generates substantial income for exporting nations — Vietnam's aquaculture sector generates over $8 billion/year in exports, primarily shrimp. In coastal communities with limited livelihood options, shrimp farming provides rural employment, reduces poverty, and contributes significantly to GDP. The returns per hectare from shrimp ponds ($ 5,000–15,000/ha/yr) are far higher than alternative uses of mangrove land.
3. Step 3
  Economic argument AGAINST clearing mangroves: (1) Shrimp ponds have a limited productive lifespan — typically 5–10 years before the accumulation of waste products, disease and salinisation renders them unproductive. The cleared mangrove cannot be restored once the pond fails, creating permanently degraded land. (2) The ecosystem services of mangroves have been valued economically — including fishery support, coastal protection, and carbon storage — at $33,000–57,000/ha/yr in some studies, far exceeding shrimp pond income. When these externalities are included, the economic case for clearing mangroves collapses. (3) Wild shrimp fisheries (dependent on mangrove nurseries) are reduced, undermining livelihoods of traditional fishers who receive none of the aquaculture income.
4. Step 4
  Policy recommendation — Integrated mangrove-shrimp farming (silvofishery): Governments should mandate and incentivise silvofishery systems, in which shrimp are farmed within partially cleared mangroves at much lower stocking densities. Trees are retained in 60–70% of the area; shrimp are reared in channels within the forest rather than open ponds. Justification: silvofishery maintains most ecosystem services (coastal protection, fish nursery, carbon storage) while allowing shrimp production. Yields per hectare are lower than intensive ponds, but the ponds remain productive indefinitely without the 5–10 year abandonment cycle. Several Vietnamese provinces have mandated silvofishery — evidence shows it is economically viable and ecologically superior.
Answer
Mangrove services lost: fish nursery (75% of commercial species), coastal storm protection, blue carbon sequestration, water filtration. Economic FOR clearing: $8bn Vietnam exports, rural employment. AGAINST: ponds productive only 5–10 years; ecosystem service value$ 33,000–57,000/ha/yr exceeds shrimp income; wild fishery harm. Policy: silvofishery (60–70% mangrove retention, shrimp in channels) — sustainable yield, maintains ecosystem services.
Examiner tip
The 35% mangrove loss statistic from the prompt and the 75% fish species nursery dependency are powerful evidence points — use them in your answer. The silvofishery solution is the most sophisticated management recommendation for this scenario. The ecosystem service valuation argument ($33,000–57,000/ha/yr) directly counters the economic case for clearing — this contrast earns top-band marks.
5Evaluate strategies for making aquaculture more sustainable
Extended• sustainable aquaculture, innovation, evaluate
Question
The global demand for seafood is projected to increase by 40% by 2050. (a) Explain why simply expanding current intensive aquaculture methods cannot meet this demand sustainably. (b) Evaluate TWO strategies that could make aquaculture significantly more sustainable.
Step-by-step solution
1. Step 1
  Why expanding current intensive aquaculture is unsustainable: Intensive fish cage farming (particularly carnivorous species like salmon) faces three fundamental sustainability limits: (1) Fishmeal dependency: salmon require approximately 3 kg of wild-caught fish as feed for every 1 kg of salmon produced. A 40% increase in salmon production would require a proportional increase in forage fish (anchovies, herrings) harvesting — stocks that are already fully exploited. This is essentially converting wild fish into farmed fish at a net loss of protein. (2) Pollution scaling: more cages mean more waste (faeces, uneaten feed, antibiotics) discharged to the sea. Sea lice infestations intensify with higher salmon densities. The localised marine environment around cage farms is already severely degraded at current scales — expansion would extend this damage. (3) Disease amplification: higher density and larger total biomass in coastal waters increases the risk of epizootic (widespread animal) disease outbreaks. A major disease event could collapse entire regional industries, as occurred in Chile's salmon industry in 2007 (ISA virus outbreak).
2. Step 2
  Strategy 1 — Plant-based and insect-based fish feed: Replacing fishmeal with plant-derived protein (soy, algae) or insect meal (from black soldier fly larvae) reduces the wild fish dependency. Advantage: algae-based feed can now meet the essential omega-3 fatty acid requirements of farmed salmon without requiring fish oil — meaning the nutritional quality is maintained without wild fish input. Insect meal production generates far less land-use impact than soy. Limitation: soy cultivation at scale causes deforestation and land-use change; pure plant diets reduce growth rates in carnivorous species; algae cultivation at commercial scale currently remains expensive and energy-intensive.
3. Step 3
  Strategy 2 — Integrated multi-trophic aquaculture (IMTA): IMTA systems raise multiple species at different trophic levels together — for example, salmon (fed species, producing waste) + mussels (filter-feeders consuming suspended particles from salmon waste) + sea urchins/abalone (deposit feeders consuming sinking waste). This mimics natural food webs, converting salmon waste into additional harvestable species rather than depositing it on the seabed. Advantage: total nutrient pollution is dramatically reduced; additional protein (mussels, sea urchins) is produced from waste that would otherwise cause environmental damage; the system is more resilient to disease as species diversity is higher. Limitation: IMTA requires complex farm management — coordinating the timing and density of multiple species is technically demanding; market access for non-salmon species (urchin, mussel) must be developed; IMTA on commercial scale remains limited compared to monoculture cages.
4. Step 4
  Conclusion: Neither strategy alone is sufficient to meet a 40% demand increase sustainably. The most realistic path is: (1) shift production emphasis toward inherently sustainable species (bivalves, seaweed) that require no feed; (2) reform salmon and shrimp farming through IMTA and alternative feeds; (3) invest in offshore recirculating aquaculture systems (RAS) — which operate in closed loops on land with zero marine discharge. Meeting 40% more demand sustainably also requires demand-side change — reducing food waste and shifting diets toward lower-trophic-level seafood.
Answer
Intensive expansion unsustainable: fishmeal needs 3 kg wild fish per 1 kg salmon (forage fish already fully exploited); pollution scales with output; disease risk (Chile ISA 2007). Strategy 1: plant/insect feed — reduces wild fish dependency, algae preserves omega-3; soy deforestation limitation. Strategy 2: IMTA (salmon + mussels + urchins) — converts waste to harvestable biomass; complex management, limited commercial scale. Conclusion: combination + bivalve focus + demand-side change needed.
Examiner tip
The '3 kg wild fish per 1 kg salmon' ratio is a powerful quantitative argument that directly earns marks. The Chile ISA virus outbreak (2007) is the most important aquaculture disease case study. IMTA is the most sophisticated management strategy at Extended level — fewer students know it, which means mentioning it distinguishes high-mark answers. Always end with a qualified conclusion that acknowledges no single strategy is sufficient.

Key Definitions and Keywords — Marine Aquaculture

Definitions to memorise and the exact keywords mark schemes credit for marine aquaculture answers — sharpened from recent examiner reports for the 2026 0680 sitting.

Aquaculture (fish farming)
Examiner keyword
The controlled cultivation and harvesting of aquatic organisms (fish, shellfish, seaweed) in managed environments such as cages, ponds or tanks, for commercial food production.
Overfishing
Examiner keyword
The removal of fish from a population at a rate faster than the population can reproduce, leading to stock collapse. Overfishing drives aquaculture demand as wild stocks decline.
Related: aquaculture, sustainable fishing, food security
Mangrove forest
Tropical coastal forests growing in saline or brackish water, with tangled root systems that stabilise shorelines, provide nursery habitat for fish and marine organisms, protect coasts from storm surge, and store significant amounts of carbon.
Related: aquaculture, habitat destruction, coastal management
Sea lice
Parasitic copepods that attach to the skin and gills of salmon and other fish. They are a major problem in salmon aquaculture, spreading from farmed to wild fish populations and causing significant mortality in wild sea trout.
Related: aquaculture, disease spread, salmon farming
Bivalve (shellfish) farming
The cultivation of filter-feeding shellfish (mussels, oysters, clams) on ropes or seabed structures. Bivalves feed naturally on phytoplankton, require no artificial feed, and can improve water clarity — making this the most environmentally sustainable form of aquaculture.
Related: aquaculture, filter feeders, sustainable food
Fishmeal
Protein-rich powder ground from small wild-caught fish (anchovies, herrings) used to feed carnivorous farmed fish. Its use links aquaculture to wild fish stock depletion in 'forage fish' populations.
Related: aquaculture, salmon farming, wild fish stocks

Common Mistakes and Misconceptions — Marine Aquaculture

The traps other students keep falling into on marine aquaculture questions — taken from recent Cambridge IGCSE 0680 examiner reports and mark schemes — and how to avoid them.

✕Assuming all aquaculture is environmentally sustainable.
Why it happens
Students are told aquaculture reduces pressure on wild fish and assume it has no environmental cost.
How to avoid it
The environmental impact varies dramatically by species and method. Salmon and shrimp farming causes serious pollution and habitat destruction. Shellfish farming is sustainable. Always specify the type of aquaculture when discussing impacts.
✕Not mentioning mangrove destruction when discussing shrimp farming impacts.
0680 Mark Schemes 2022-2024 — mangrove destruction awarded dedicated marks.
Why it happens
Students focus on water pollution and disease but overlook habitat impacts.
How to avoid it
Mangrove destruction for shrimp ponds is the most high-profile negative impact of aquaculture in the Cambridge syllabus. It appears in mark schemes regularly. Always include it for shrimp/prawn farming examples.
✕Saying aquaculture has completely solved overfishing.
Why it happens
Students hear aquaculture is the solution to wild fish declines and take this too literally.
How to avoid it
Aquaculture currently supplies over 50% of seafood but does NOT eliminate wild fish pressure — in fact, some aquaculture (salmon farming) still requires large quantities of wild-caught fish for feed. It is a partial solution, not a complete one.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Marine Aquaculture

Detailed Notes

What you’ll learn

1Describe what marine aquaculture is and how it works

2Benefits of aquaculture for food security

3Evaluate the environmental impacts of marine aquaculture

4Evaluate the trade-off between shrimp farming and mangrove conservation in Southeast Asia

5Evaluate strategies for making aquaculture more sustainable

Aquaculture (fish farming)

Overfishing

Mangrove forest

Sea lice

Bivalve (shellfish) farming

Fishmeal

✕Assuming all aquaculture is environmentally sustainable.

✕Not mentioning mangrove destruction when discussing shrimp farming impacts.

✕Saying aquaculture has completely solved overfishing.

Past paper style quiz