What is Overfishing and How Does it Affect the Ecosystem?

Overfishing involves taking more fish from the water than is sustainable, which means the number of individuals removed is more than the breeding or recovery rate of the population.

This leads to a decline in the numbers of these species, which can happen rapidly, causing issues within the ecosystems and affecting the stability of the environment.

Research shows that global marine seafood populations could collapse by 2050, which means the species we rely on for consumption will have declined by a massive 90%.

Today, 3 billion people rely on seafood as a primary protein source, and in 2018, global fishing totals are estimated to be around 179 million tonnes each year. Studies show that at least a third of all assessed fishing practices are done so in an unsustainable way, and the species targeted are declining rapidly.

Fishing unsustainably results in economic problems, as less marine life is available to catch and sell. But what are the environmental impacts?

What Impacts Does Overfishing Have on the Ecosystem?

Overfishing Destroys Delicate Ecosystems

The major problem with overfishing is that it depletes the amount of marine life in the water, which causes ecosystems to collapse. This drives further environmental destruction, as each species plays a vital role in maintaining its habitat’s health.

Specific species are often targeted in the fishing industry concerning what consumers want, leaving many environments depleted of a vital food chain member.

The coral triangle in Southeast Asia faces overfishing issues of many species, including tuna, which is one of the worst affected.

Extensive fishing practices often take advantage of marine life that gathers in large numbers, sometimes to hunt for safety or to spawn at specific times of the year. Collecting fish this way can quickly reduce populations because many reproducing adults are caught at once, producing fewer offspring or making it to adulthood.

This negatively impacts species further down the food chain, and when fishing occurs on coral reefs using nets, it is generally the herbivorous fish that are caught. These fish are essential in keeping the reef healthy by preventing other species from overpopulating and balancing algae levels.

Fewer marine creatures on the reef to keep it healthy means the coral is more exposed to extreme weather events and climatic changes like increases in water temperature that lead to the death of the coral reefs.

Overfishing Leads to More Marine Environments Being Targeted

It is a vicious cycle. Overfishing leads to fewer fish in the ocean, so boats must venture into new locations, or trawlers go to deeper parts of the sea, which destroys even more ecosystems.

To put this in perspective, despite the number of fishing boats doubling between 1950 and 2015, the number of fish caught compared to the effort was a fifth less. This means more areas are being fished, but fewer fish are caught each time.

Trawling drives overfishing as it involves the wasteful practice of dragging large nets, sometimes miles long, through the ocean or across the seabed, which catches every animal in its path.

Overfishing Causes the Decline of Other Marine Animals

Reducing the number of fish in the ocean affects the food sources of many other marine animals and leads to a decline in their numbers.

Overfishing also results in many creatures ending up as bycatch, particularly with trawling fishing practices, as the nets catch every animal in the area. This means many marine mammals, such as whales, dolphins, and porpoises, as well as turtles, sharks, and even seabirds, die in these nets, which has a dramatic impact on the environment.

One-third of all sharks, rays, and related species are at risk of extinction because of overfishing, and at least 650,000 marine mammals are caught as bycatch in nets each year.

Ocean or Lake Dead Zones

Damage to an ecosystem’s biodiversity can cause ocean or lake dead zones, which are areas with low oxygen levels that most organisms cannot survive in. Worldwide, around 400 ocean dead zones are more significant than in the United Kingdom or Oregon.

Overfishing can lead to these dead zones because essential species, like Cod, are lost, which unbalances the ecosystem and can increase certain species, such as algae.

With no other species to regulate numbers, algae can multiply, leading to large algal blooms that take oxygen out of the water and starve the water.

Therefore, populations of other species are forced to leave or even die out, damaging the ecosystem.

Why Does Overfishing Happen?

Fishing is not Well Managed or Controlled

Even though research highlights the adverse effects overfishing has from both an environmental and economic perspective, it is still commonplace because the industry is poorly governed and managed.

Governments are hesitant to place stricter controls on fishing or tackle illegal fishing because of the industry’s enormous economic benefits.

The nature of the ocean, being so vast with no clearly defined borders, also poses an issue for implementing policies and control measures.

Harmful Subsidies Fuel Overfishing

Subsidies are generally used to support economic growth in specific industries. However, harmful subsidies provided for certain fishing practices cause problems such as overfishing, as they fund sectors that would not make a profit without them.

An example of this is subsidies to build new fishing vessels or those for industrial trawling boats to cover fuel costs.

Research outlines that in 2018, over $20 billion of subsidies were used to fund unsustainable fishing practices worldwide that led to overfishing.

Subsidies are not necessarily the problem, but they are what this funding is supporting. Currently, this model results in overfishing—as fish stocks decrease, fishing efforts must increase for the companies to profit. This is unsustainable and part of the reason fish stocks are so low.

Fishing is a Big Part of Many Cultures

It is crucial to outline that many cultures and communities rely on fishing for survival and have done so for many years. Fishing in a small-scale operation using knowledge, experience, and respect for the local ecosystems is not the issue.

Biodiversity suffers when organizations use these resources and local knowledge about species’ behavior or habitat to maximize profit.

What Can We Do to Stop Overfishing?

Consume Less Fish

One of the best ways to prevent overfishing is to reduce the amount of fish you consume and ensure the fish you eat is caught sustainably. This is particularly relevant if you live in a developed country and eat fish imported from other parts of the world, as you cannot guarantee the sustainability of these fishing practices.

It is more complex than trusting labels that claim fishing regulations are followed, as this needs to be managed globally. If you purchase fish, shop locally, choose sustainable species, and buy from trusted brands.

Introduce Policies

Governments and global organizations need to work together to end illegal fishing, adjust subsidies to promote sustainable fishing, and introduce policies that prevent overfishing.


Funding research into fish populations, the health of marine ecosystems, and the effects of current fishing techniques will also reduce overfishing as there are precise data to support laws and policies.

Additionally, changes are more likely to occur if we share the idea that eliminating overfishing will have economic benefits for the fishing industry and environmental benefits due to more abundant marine life populations.

Creating More Marine Parks

Creating more Marine Parks where fish are protected is a fantastic way to support ecosystems. It provides safe areas for fish to live and reproduce, stabilizing populations.

Research has shown that implementing protected marine areas can increase fish populations by 400% in just 11 years, allowing ecosystems to recover yet still allowing designated areas where fishing can occur.

Support and Promote

Supporting and promoting the rights of local, small-scale fishing communities and learning to appropriately protect marine life will also help transform ecosystems worldwide.

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