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examBoard: Cambridge
examType: IGCSE
lessonTitle: Case Study: Marine Species Farming
Marine species farming, also known as aquaculture or mariculture, is the farming of aquatic organisms in marine environments. As wild fish stocks decline worldwide due to overfishing and habitat destruction, marine farming has become increasingly important for food security and reducing pressure on wild populations.
Key Definitions:
Aquaculture now provides over 50% of all fish consumed globally. With the world's population growing and wild fish stocks declining, marine farming is crucial for meeting future protein needs. The industry has grown at an average annual rate of 5.8% since 2000 and now produces over 80 million tonnes of food annually.
The global aquaculture market is valued at over £200 billion and provides employment for more than 20 million people worldwide. For coastal communities, marine farming offers sustainable livelihoods and economic resilience, especially in regions where traditional fishing has declined.
Different marine species require different farming methods. The choice of system depends on the species being farmed, local environmental conditions and economic factors.
Large cages or pens placed in open ocean waters. Used mainly for fish like salmon and tuna. These systems benefit from natural water circulation but face challenges from storms and predators.
Located in protected bays or estuaries. Common for shellfish like mussels and oysters. These areas provide natural protection but may have limited water exchange and higher pollution risks.
Tanks or ponds filled with seawater. Suitable for high-value species like shrimp. These systems offer complete environmental control but require significant energy for water pumping and treatment.
A wide variety of marine species are farmed commercially around the world, each with specific requirements and market values.
Atlantic Salmon: The most valuable farmed marine fish globally, primarily produced in Norway, Chile, Scotland and Canada.
Sea Bass and Sea Bream: Popular in Mediterranean countries, these species are well-suited to warmer waters.
Tuna: High-value species that is increasingly farmed, though technical challenges remain.
Mussels: Filter feeders that require no additional feed, making them environmentally friendly to farm.
Oysters: Valuable both as food and for their ability to filter and clean water.
Shrimp: One of the most valuable seafood commodities, farmed extensively in Asia and Latin America.
Like any food production system, marine farming has both positive and negative environmental impacts. Understanding these impacts is crucial for developing sustainable practices.
Scotland is the third-largest producer of farmed Atlantic salmon globally, with an industry worth over £1 billion annually. The industry employs around 2,500 people directly, with thousands more in supporting sectors. Scottish salmon farms use sea cages located in sheltered sea lochs along the west coast and islands.
While economically important, the industry faces environmental challenges including sea lice infestations, which can spread to wild salmon and waste accumulation beneath cages. In response, companies are investing in technologies like closed containment systems, underwater cameras to monitor feeding efficiency and cleaner fish (like wrasse) that eat sea lice without chemicals.
The Scottish government has implemented strict regulations requiring environmental monitoring and reporting. Farms must measure their impact on the seabed and water quality, with penalties for those exceeding acceptable limits.
As the industry grows, sustainable management practices are becoming increasingly important to minimise environmental impacts while maximising production.
Choosing appropriate locations with good water circulation, appropriate depth and away from sensitive habitats is crucial. Environmental impact assessments should be conducted before establishing new farms.
Developing feeds that reduce reliance on wild fish and minimise waste is essential. Plant-based proteins, insect meal and algae are increasingly used as sustainable alternatives.
Implementing biosecurity measures, vaccines and non-chemical treatments helps prevent disease outbreaks and reduces the need for antibiotics and pesticides.
One of the most promising approaches to sustainable marine farming is Integrated Multi-Trophic Aquaculture (IMTA), which mimics natural ecosystem relationships.
In IMTA systems, multiple species from different trophic levels are farmed together. For example, fish produce waste that is then utilised by shellfish and seaweeds, creating a mini-ecosystem where one species' waste becomes another's food. This approach can significantly reduce environmental impacts while increasing overall productivity.
In the Bay of Fundy, researchers have developed an IMTA system that combines Atlantic salmon with mussels and kelp. The salmon are fed commercial feed, producing waste that contains nutrients. The mussels filter small particles from the water, while the kelp absorbs dissolved nutrients.
Research has shown that mussels grown near salmon cages grow faster than those in control sites due to the additional food particles. Similarly, kelp grows more quickly when positioned near salmon cages because of the higher nutrient levels.
This system not only reduces the environmental footprint of salmon farming but also produces additional valuable crops. The kelp can be harvested for food products or biofuel, while the mussels provide additional seafood for human consumption.
Certification schemes help consumers identify responsibly farmed seafood and incentivise farmers to adopt sustainable practices.
Aquaculture Stewardship Council (ASC): Sets standards for responsible aquaculture, covering environmental and social impacts.
Global Aquaculture Alliance (GAA): Provides Best Aquaculture Practices (BAP) certification for farms, processing plants and feed mills.
Organic Certification: Various schemes exist for organic aquaculture, prohibiting synthetic chemicals and requiring sustainable feed sources.
Informed consumers can drive industry improvements by choosing certified products. Retailers increasingly require certification from their suppliers, creating market pressure for better practices.
Apps like the Marine Conservation Society's "Good Fish Guide" help consumers make sustainable choices when buying seafood, including farmed products.
Technological innovations and new approaches are helping address current challenges and expand the potential of marine farming.
Moving farms further offshore into deeper waters can reduce conflicts with coastal users and environmental impacts. New technologies like submersible cages and automated feeding systems make this possible.
Land-based systems that recycle water reduce environmental impacts and allow farming in non-coastal areas. Though energy-intensive, they offer complete control over growing conditions.
Research into farming new species can reduce pressure on popular species and create more resilient industry. Species like cobia, grouper and various seaweeds show promise.
Marine species farming plays a crucial role in global food security and will become increasingly important as the world's population grows and wild fish stocks continue to face pressure. While the industry faces environmental challenges, sustainable management practices, technological innovations and integrated approaches like IMTA offer pathways to responsible development.
For students interested in environmental management, marine farming represents an important case study in balancing food production needs with environmental protection. The future of the industry will depend on continued improvements in technology, management practices and regulatory frameworks to ensure that marine farming contributes positively to both human nutrition and ocean health.
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