4.3 Aquatic Food Production Systems

Phytoplankton

Microscopic photosynthetic organisms that float in water and form the base of aquatic food webs, producing over half of Earth’s oxygen.

Macrophytes

Large aquatic plants visible to the naked eye that photosynthesise and provide energy for aquatic food webs.

Aquatic food web

A network of interconnected food chains showing the flow of energy and matter between aquatic organisms.

Food chain

A simple linear model showing energy transfer from one organism to another through feeding relationships.

Trophic level

The position an organism occupies in a food chain or food web based on its feeding role.

Primary producers

Organisms such as phytoplankton and macrophytes that produce biomass using photosynthesis.

Primary consumers

Organisms such as zooplankton and small fish that feed directly on primary producers.

Secondary consumers

Organisms such as larger fish, dolphins or whales that feed on primary consumers.

Tertiary consumers

Apex predators such as sharks or seals that feed on secondary consumers.

Whale pump

The process by which whales mix ocean layers and release nutrient

Productivity

The rate at which biomass or organic matter is produced through photosynthesis in an ecosystem.

Thermal stratification

Layering of water in lakes or oceans due to temperature differences, affecting nutrient mixing and productivity.

Nutrient mixing

The movement of nutrients between water layers, supporting productivity in aquatic ecosystems.

Upwelling

The upward movement of cold, nutrient

Nutrient loading

The input of excess nutrients into water bodies from human activities such as agriculture and urbanisation.

Eutrophication

The process where excess nutrients cause algal blooms, oxygen depletion and reduced aquatic biodiversity.

Blue foods

Foods harvested from aquatic environments, including fish, shellfish and aquatic plants.

Maximum sustainable yield (MSY)

The highest annual catch of a species that can be maintained over time without depleting the population.

Fishing effort

The amount of work, time and resources used to harvest fish within a given area or time period.

Overfishing

Fishing beyond the MSY that reduces fish populations faster than they can recover.

Fishing quota

A limit on the amount of a specific fish species that can be caught, set by governments to ensure sustainable fishing by preventing overfishing, often based on scientific assessments of fish stocks.

Renewable resource

A resource that can regenerate naturally at the same rate it is consumed, such as fish stocks.

Natural capital

Natural resources valued for their usefulness to humans, such as fish populations.

Natural income

The yield harvested from natural capital, such as fish caught from the sea.

Tragedy of the commons

A situation where shared resources are overused because individuals act in their own self

Commoning

Principles for managing shared resources collectively to reduce the risk of overexploitation.

Acoustic survey

A method of estimating fish populations using sound waves and analysing their echoes.

Fish tagging

The use of electronic tags to track fish movements and estimate population sizes.

Electronic monitoring

The use of cameras and digital systems on fishing vessels to track catch levels and enforce quotas.

Unsustainable harvesting

Fishing practices that damage habitats, produce high bycatch or deplete fish populations.

Bycatch

the unwanted fish and other marine creatures caught during commercial fishing for a different species.

Ghost fishing

The continued trapping of marine organisms by lost or abandoned fishing gear.

Bottom trawling

A fishing method where nets are dragged along the seafloor, causing habitat damage and bycatch.

Pelagic trawling

A fishing method using cone-shaped nets towed through the open water column by one or two boats to catch schooling fish without touching the seabed, thus avoiding habitat damage but potentially creating bycatch issues

Blast fishing

The use of explosives to stun or kill fish, causing severe habitat destruction.

Poison fishing

The use of toxic substances such as cyanide to capture fish, harming ecosystems.

Fishery collapse

The failure of a fish population due to prolonged overexploitation, such as the Newfoundland cod collapse.

Exclusive economic zone (EEZ)

An ocean area extending 370 km from a country’s coast where it has rights to regulate fishing.

UNCLOS

The United Nations Convention on the Law of the Sea, establishing rules for ocean use and fishing rights.

High seas

Ocean areas beyond national EEZs with limited international regulation.

Environmental justice

A concern that environmental benefits and burdens are shared fairly among different communities.

Animal rights

The ethical view that animals have moral value and should not be exploited unnecessarily.

Indigenous hunting

Traditional harvesting practices essential for the survival and culture of indigenous peoples.

Ocean acidification

The decrease in ocean pH caused by absorption of atmospheric CO2 forming carbonic acid.

Carbonic acid

A weak acid formed when carbon dioxide dissolves in seawater, lowering ocean pH.

Coral reef

A marine ecosystem built from calcium carbonate skeletons of coral polyps.

Coral bleaching

The loss of symbiotic algae from corals due to heat stress, causing corals to turn white and weaken.

Resilience

The ability of an ecosystem to resist and recover from disturbances.

Coral gardening

A reef restoration technique where corals are grown and transplanted to damaged reefs.

Marine protected area (MPA)

An ocean region where human activities are restricted to protect ecosystems and fish stocks.

Spillover effect

The movement of fish from MPAs into surrounding waters, supporting fisheries outside protected zones.

Aquaculture

The farming of aquatic organisms such as fish, shellfish and seaweed.

Fishmeal

A high-protein animal feed made from ground, dried fish or fish by-products, commonly used in aquaculture and livestock farming.

Antifouling agents

Chemicals used to prevent organism growth on aquaculture equipment that can harm ecosystems.

Integrated aquaculture

A system where multiple species such as fish, seaweed and shellfish are farmed together to reduce waste.

Illegal, unreported and unregulated (IUU) fishing

Fishing activities that violate laws, avoid reporting or operate without regulation.

Environmental law

Rules governing how humans use natural resources to promote sustainability.

International cooperation

Collaboration between countries to manage shared fish stocks and prevent overfishing.

Consumer choice

The role of individual purchasing decisions in supporting sustainable fishing practices.

Sustainable seafood certification

Labelling systems that indicate fish have been harvested using sustainable methods.

Recovery of fish stocks

The gradual increase of overexploited populations through regulation, protection and cooperation.