Fishery collapse occurs when fish are harvested faster than populations can reproduce, causing stocks to fall below levels that can sustain continued fishing. This is overexploitation, often intensified by demand, efficient technology and weak regulation.
Level: SL and HL: Subtopic 4.3 Aquatic food production systems
How Overexploitation Causes Collapse
A fish population replaces losses through reproduction. When catches exceed replacement, the breeding population shrinks, so fewer young fish are produced and the stock declines. Fishers may increase effort to maintain catches, accelerating depletion.
The maximum sustainable yield (MSY) is the highest annual catch that can theoretically be sustained over time. Collapse can occur when catches exceed MSY, or when uncertain stock data cause MSY to be overestimated.
| Cause | Contribution to collapse |
|---|---|
| Rising seafood demand | Higher prices encourage larger catches. |
| Industrial fishing technology | Sonar, factory ships and large nets capture fish faster than stocks recover. |
| Open-access resources | Immediate private benefits but shared depletion costs create a tragedy of the commons. |
| Weak governance | Poor quotas, enforcement and control of illegal fishing permit excessive harvests. |
| Bycatch and habitat damage | Non-target species are killed, while trawling damages breeding and nursery grounds. |
| Environmental change | Climate change and ocean acidification reduce resilience and recovery. |
The collapse of the Grand Banks cod fishery off Newfoundland is a named example. Industrial harvesting and overestimated stocks severely reduced cod numbers, leading Canada to impose a moratorium in 1992. The collapse removed livelihoods from fishing communities, showing that management must address social, economic and ecological sustainability.