5.5 Case Studies — Oceans and Fisheries

2026 Syllabus Objectives

By the end of this subtopic, you should be able to:

  1. Study the resource potential, exploitation, impact and management of a marine fishery.
  2. Study an example of farming of marine species, including the source of food, pollution from waste, and impact on the natural habitat.

Objective 1: A Marine Fishery — The North Atlantic Cod Fishery

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What is a Marine Fishery?

A marine fishery is an area of the ocean where fish and other sea creatures are caught in large numbers for food or trade. Fisheries are incredibly important — they feed hundreds of millions of people around the world and provide jobs for coastal communities.

Resource Potential

Resource potential means how much a fishery could produce if used wisely and sustainably.

  • The North Atlantic Ocean — particularly the Grand Banks off the coast of Canada and Newfoundland — was once one of the richest fishing grounds on Earth.
  • The cold, nutrient-rich waters supported enormous populations of Atlantic cod (Gadus morhua), along with haddock, herring, and other species.
  • For centuries, cod were so plentiful that fishermen described the sea as almost "boiling" with fish.
  • Cod reproduce quickly under healthy conditions, meaning the population can naturally replenish itself — if humans do not take more than the sea can replace.

Key idea: A fishery has high resource potential when fish breed faster than they are caught. This is called a sustainable yield — the amount you can take without shrinking the population.

Exploitation

Exploitation means how humans use (and often overuse) a resource.

  • For hundreds of years, cod were caught using simple nets and small boats. The catches were large, but the fish population could recover.
  • In the 20th century, technology changed everything:
    • Factory ships — giant vessels that could catch, process, and freeze thousands of tonnes of fish at sea without ever returning to port.
    • Sonar and GPS technology — allowed fishermen to locate exactly where large shoals (groups) of fish were hiding.
    • Trawling — huge nets dragged along the seafloor scooped up enormous quantities of fish, including young fish that had not yet had a chance to breed.
  • The result: fish were being caught far faster than they could reproduce.
  • By the 1990s, cod stocks in the Grand Banks had collapsed — the population had fallen by over 95% from its original size.
  • In 1992, Canada declared a moratorium (a complete ban) on cod fishing in the area, putting tens of thousands of fishermen out of work overnight.

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