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examBoard: Cambridge
examType: IGCSE
lessonTitle: Overfishing of Marine Species
Overfishing occurs when fish are caught faster than they can reproduce and replenish their populations. It's one of the most serious threats to our oceans today, affecting marine ecosystems worldwide. Nearly 90% of the world's fish stocks are now fully exploited, overexploited or depleted, putting the future of our oceans and the livelihoods of millions of people at risk.
Key Definitions:
Global fishing fleets are 2-3 times larger than what our oceans can sustainably support. Since the 1970s, we've removed more than 90% of large predatory fish like tuna, swordfish and sharks from the world's oceans. Every year, about 80 million tonnes of fish are caught worldwide, with an additional 20 million tonnes discarded as bycatch.
Oceans provide food security for billions of people, with fish supplying about 17% of animal protein consumed globally. Beyond food, healthy fish populations maintain marine ecosystem balance. Overfishing disrupts food webs, destroys habitats and threatens the livelihoods of 820 million people who depend on fisheries for income and nutrition.
Several interconnected factors have led to the current overfishing crisis in our oceans:
Global fish consumption has doubled since the 1960s. With the world population expected to reach 9.7 billion by 2050, demand continues to rise, putting pressure on already strained fish stocks.
Modern fishing vessels equipped with sonar, GPS and satellite communications can locate fish with incredible precision. Factory ships can process and freeze catch at sea, allowing fleets to stay out longer and fish more intensively.
Government subsidies (about $35 billion annually) keep many fishing operations profitable even when fish stocks decline. This creates economic incentives to continue fishing beyond sustainable levels.
Several fishing methods cause particular harm to marine ecosystems:
Enormous nets are dragged along the seafloor, capturing everything in their path. This method destroys delicate seafloor habitats like coral reefs and seagrass beds that serve as nurseries for many species. A single pass of a trawl net can destroy marine habitats that took centuries to form.
Lines up to 80 km long with thousands of baited hooks catch many non-target species. Each year, longlines kill an estimated 300,000 seabirds, including endangered albatrosses, along with thousands of sea turtles and sharks as bycatch.
Overfishing disrupts marine ecosystems in complex and far-reaching ways:
When key species are removed from marine ecosystems, it creates a ripple effect throughout the food web:
The collapse of the North Atlantic cod fishery off Newfoundland, Canada, stands as one of the most dramatic examples of overfishing. For centuries, these waters were among the richest fishing grounds in the world. By the 1960s, massive factory trawlers were harvesting 800,000 tonnes of cod annually.
Despite warning signs of population decline in the 1980s, fishing continued until 1992, when the Canadian government declared a moratorium after stocks had collapsed by 99%. This led to the loss of 40,000 jobs and devastated coastal communities. Despite nearly 30 years of protection, cod stocks have shown only minimal recovery, demonstrating how overfishing can cause long-term or permanent ecological damage.
Overfishing affects not just marine life but human communities as well:
More than 3 billion people rely on fish as their primary source of protein and about 820 million people depend directly or indirectly on fisheries for their livelihoods. When fish stocks collapse, these communities face food insecurity, unemployment and economic hardship. Small-scale fishers are particularly vulnerable, as they lack the resources to travel further offshore or switch to alternative livelihoods.
The World Bank estimates that overfishing results in $83 billion in lost economic benefits annually. As fish become scarcer, fishing becomes more expensive and less profitable. This creates a vicious cycle where fishers must catch more fish to maintain their income, further depleting stocks. Developing nations that depend heavily on fishing for export income and food security are disproportionately affected.
Addressing overfishing requires a combination of scientific, regulatory and market-based approaches:
Several approaches have proven effective in restoring fish populations while maintaining fishing livelihoods:
The United States has made significant progress in rebuilding overfished stocks through the Magnuson-Stevens Fishery Conservation and Management Act. Since 2000, 45 fish stocks have been rebuilt to sustainable levels. Key to this success has been setting science-based catch limits, holding fisheries accountable for staying within these limits and implementing rebuilding plans with firm deadlines.
For example, the Atlantic sea scallop fishery was near collapse in the early 1990s. Through a combination of rotating closed areas, reduced fishing days and gear modifications, the fishery recovered dramatically. Today, it's one of the most valuable and sustainable fisheries in the U.S., worth over $500 million annually.
Since fish don't respect national boundaries, international cooperation is essential:
The UN Fish Stocks Agreement and the FAO Code of Conduct for Responsible Fisheries provide frameworks for international cooperation. Regional Fisheries Management Organizations (RFMOs) manage fish stocks in international waters. However, enforcement remains challenging, with illegal, unreported and unregulated (IUU) fishing accounting for up to 26 million tonnes of fish annually.
Consumers can help by making informed choices. Certification schemes like the Marine Stewardship Council (MSC) and seafood guides help identify sustainable options. By choosing sustainable seafood, consumers create market demand for responsibly caught fish. Apps like the Good Fish Guide help shoppers make sustainable choices at the supermarket or restaurant.
The good news is that fish populations can recover when given the chance. Studies show that reducing fishing pressure allows most stocks to rebuild within 10 years. With proper management, our oceans can continue to provide food and livelihoods for generations to come.
The challenge of overfishing requires action at all levels from international agreements to individual consumer choices. By understanding the causes and consequences of overfishing, we can all contribute to healthier oceans and more sustainable fisheries.
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