4.3 Aquatic food production systems

 Phytoplankton and macrophytes

provide energy for freshwater and marine food webs, both are autotrophs and primary producers.

Phytoplankton

are a type of microscopic plankton capable of photosynthesis that are found in oceans, seas and freshwater

Macrophytes

are aquatic plants that are large enough to be visible. They can be emergent from water, submerged or floating

Humans consume organisms from

freshwater and marine environments, from farmed and wild sources

Demand for foods from freshwater and marine environments is increasing

due to the growth in human population and changes in dietary preferences, this demand has come from an increase in aquaculture while capture fisheries have plateaued.

The increasing global demand for seafood

has encouraged use of unsustainable harvesting practices and overexploitation.

Bottom trawling

Large nets are dragged along the seafloor, this destroys habitats like coral reefs and seagrass beds

Ghost fishing

Lost or abandoned fishing gear continues to trap fish and other marine animals, it wastes marine life and harms species like turtles and dolphins

Use of poisons and explosives

Poisons (like cyanide) and explosives are used to catch fish quickly.
These methods kill many other species and damage marine ecosystems

Overexploitation has led to the collapse of fisheries

The World Bank reports that almost 90% of global marine fish stocks are either fully exploited or overfished, indicating unsustainable fishing practices, Ex. Cod Fishery Collpase Grand Banks, Newfoundland

Maximum Sustainable Yield (MSY)

the highest possible annual catch that can be sustained over time, so it should be used to set caps on fishing quotas.

Climate change and ocean acidification

are having impacts on ecosystems and may cause collapse of some populations in freshwater or marine ecosystems

Climate Change leads to oceans becoming warmer, having less oxygen, and becoming more acidic, causing

Rising Sea Levels, Coral Bleaching, Toxic Algae, Habitat Destruction, Acidification, Fisheries Collapse

 Unsustainable exploitation of freshwater and marine ecosystems can be mitigated

through policy legislation addressing the fishing industry and changes in consumer behaviour

International Policy & Agreements

the EU is part of many international agreements to manage fish stocks, e.g., with Norway, Iceland, Guinea-Bissau, and Greenland, the International Commission for the Conservation of Atlantic Tunas (ICCAT) and the Convention on International Trade in Endangered Specie (CITES) help regulate marine species and trade, the Committee on Fisheries works under the UN’s Food and Agriculture Organization (FAO)

National Policies

USA Magnuson-Stevens Act to prevent overfishing, rebuild fish populations, ensure long-term benefits and sustainable seafood, and protect essential fish habitats, Permits, quotas, and fishing seasons help manage when and how much fish can be caught in specific areas, Control net mesh size can be adjusted to reduce bycatch (unwanted fish), and Zoning is used to control where fishing can take place

Consumer Behaviour

documentaries like Seaspiracy and End of the Line raise awareness, labels like the Marine Stewardship Council (MSC) guide consumers to choose, fish from healthy stocks, well-managed fisheries, and options that minimize harm to ecosystems

Marine protected areas (MPAs)

can be used to support aquatic food chains and maintain sustainable yields, they protected area can benefit wider areas of sea, for example, by providing shelter, or spawning grounds. This allows fish stock to recover.

Aquaculture

the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants, the industry is expanding to increase food supplies and support economic development, but there are associated environmental impacts

Aquaculture Negative Impacts

loss of habitat, pollution with feed, anti-fouling agents, antibiotics and other medicines used, spread of diseases, and escapees which, in some cases, are genetically modified. 

Managing environmental impacts of aquacultures

reducing waste from uneaten feed, regular removal of dead fish from cages, moving cages at regular intervals to prevent buildup of organic sediments and given the area time to recover, locate fish farms where there is movement and exchange of water, aerate the water to prevent anoxic conditions, using predator resistant materials