In the early 1960s the world ate under 30 million tonnes of aquatic food a year. Today it is over 150 million. That is not just more people — it is richer people, eating differently, supplied by a global trade network that barely existed then.
📘 What you need to know
Humans eat both flora and fauna from freshwater and marine environments.
Consumption patterns vary locally and globally, shaped by availability, tradition and sustainability concerns.
Demand has risen sharply over the last 50–100 years.
The main drivers are population growth, changing diets, nutritional value, urbanisation and a growing middle class, global trade and aquaculture.
Capture fisheries have levelled off while aquaculture has grown enormously.
Seafood supplies useful nutrients including omega-3 fatty acids, vitamins and minerals.
What people actually eat
Aquatic food is not just fish. Seaweeds and freshwater algae are eaten worldwide, and some of the most valuable harvests are shellfish.
Organism
Type
Environment
Reach
How it is produced or gathered
Watercress
Flora
Freshwater
Local
Grown in shallow flowing beds fed by springs; eaten in salads and soups, popular in the UK
Spirulina
Flora
Freshwater
Global
Cyanobacteria grown in ponds and lakes, filtered out and dried as a dietary supplement
Dulse
Flora
Marine
Local
Red seaweed hand-picked from rocks at low tide and dried; traditional in Ireland
Nori
Flora
Marine
Global
Red seaweed farmed on nets in coastal water, dried into sheets; central to Japanese cuisine
Trout
Fauna
Freshwater
Local
Raised in ponds or tanks with controlled water quality, netted at market size
Tilapia
Fauna
Freshwater
Global
Farmed in ponds or recirculating systems; one of the most widely eaten farmed fish
Scallops
Fauna
Marine
Local
Hand-collected by divers from the seabed, which avoids the damage caused by dredging
Shrimp
Fauna
Marine
Global
Raised in coastal ponds or tanks and harvested by draining and netting
Notice the pattern. The local foods tend to be gathered by hand or grown in small operations. The global ones are farmed at scale and shipped worldwide. That difference in production method is usually where the environmental impact lies.
How much demand has grown
Always separate the two causes. Some of this rise is extra people; a large part is each person eating roughly twice as much aquatic food as their grandparents did.
Six reasons demand keeps climbing
Population growth. More people means a bigger consumer base for every food, seafood included.
Changing diets. As economies grow, people shift towards protein-rich foods, and seafood is one of them.
Nutritional reputation. Seafood is valued for omega-3 fatty acids, vitamins and minerals, so health advice pushes consumption up.
Urbanisation and the middle class. City living and rising incomes create demand for varied, higher-value foods.
Global trade. Refrigerated transport and trade networks mean fish caught in one ocean is eaten on another continent days later.
Aquaculture. Farming has grown fast enough to supply demand that wild stocks could never have met.
Where the supply now comes from
This is the graph to understand. Capture fisheries grew until roughly 1990 and then flattened — the ocean simply could not yield more. Everything since has come from farming.
The flat green bars are the story. Once wild catch plateaued, every extra tonne of seafood the world ate had to be farmed — which is why the aquaculture page matters so much.
If a data question gives you this graph, describe both trends separately before comparing them. “Capture rises then plateaus at about 70 Mt, while aquaculture rises continuously and overtakes it” is a full-mark description.
Worked examples
WORKED EXAMPLE 1
Percentage increase in consumption
Global aquatic food consumption rose from about 28 million tonnes in 1961 to about 158 million tonnes in 2019. Calculate the percentage increase.
Step 1: find the change158 − 28 = 130 million tonnesStep 2: divide by the original and multiply by 100130 ÷ 28 × 100 = 464%An increase of about 464%, or roughly 5.6 timesalways divide by the original value — dividing by the new one is the most common error in this calculation
WORKED EXAMPLE 2
Separating population growth from diet change
World population was about 3.1 billion in 1961 and about 7.7 billion in 2019. Using the consumption figures above, calculate seafood consumption per person for each year and comment.
Step 1: 196128 × 109 kg ÷ 3.1 × 109 = 9.0 kg per personStep 2: 2019158 × 109 kg ÷ 7.7 × 109 = 20.5 kg per personStep 3: interpret
Population rose about 2.5 times but consumption per person more than doubledBoth more people and richer diets, roughly equallythis is the analysis examiners want — not just “because population increased”
WORKED EXAMPLE 3
Describe the trends in the second graph [3]
Write a full-mark data description.
Point 1: capture fisheries
Rise from about 40 Mt in 1970 to about 70 Mt by 2010, then level offPoint 2: aquaculture
Rises continuously and steeply, from about 3 Mt to about 88 Mt
Point 3: comparison
Aquaculture overtakes capture fisheries between 2010 and 2020
Quote figures and give the shape of each trenddescription means what the data shows; save the explanation for a separate question unless asked
💡 Exam tip
Give both flora and fauna examples. Seaweed and spirulina show you have read past “fish”.
Distinguish local from global foods, and freshwater from marine.
Separate more people from more per person when explaining rising demand.
Learn the plateau in capture fisheries. It is the single most useful fact in this section.
Quote figures with about, and always give units (million tonnes).
Mention omega-3 when nutritional value comes up — it is the named example in the syllabus material.
⚠ Common mix-up
Thinking aquatic food means only fish. Seaweeds, shellfish and algae are all part of it.
Blaming population alone. Consumption per person has roughly doubled as well.
Reading the plateau as a fall. Capture fisheries have stayed roughly level, not declined sharply.
Assuming aquaculture is automatically sustainable. That comes with its own problems, covered later.
Dividing by the wrong value in percentage change questions.
Describing when asked to explain, or the other way round. Check the command term.
Up next: Overfishing and Damaging Harvest Methods — what happens when that rising demand meets a finite ocean, and how a fishery collapses.
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