The Dangers of Overfishing

Today is day 3 of Rivers to Oceans Week here in Canada, and as such, we decided to publish an article focusing specifically on some of the dangers of overfishing. This includes impacts to local economies and employment, in addition to numerous ecological repercussions.


Fishing is one of the most significant forces behind the major declines in ocean wildlife populations around the world. While catching fish is not inherently bad for the ocean, the practices of commercial fisheries can result in vessels catching fish faster than their stocks can replenish. This occurrence is called overfishing.

According to the Food & Agriculture Organization of the United Nations, the number of overfished stocks has tripled in the past half century, and today, one-third of the world’s assessed fisheries are being pushed beyond their biological limits. Overfishing is closely tied to bycatch; this refers to all the other marine life caught while attempting to catch a target species. For instance, a fishing boat may put their net in the water aiming to catch all of one type of fish (see figure 1), but in reality, they are likely to also get some bycatch, which can include other aquatic animals such as dolphins or sea turtles (see figure 2).

Figure 1 – Target Species in Net
Figure 2 – Bycatch in Net

Bycatch is a serious threat to marine ecosystems that cause the loss of billions of fish, along with thousands of sea turtles and other aquatic species. According to the documentary Seaspiracy, 40% of everything caught gets thrown back into the water as bycatch; most of which die before they even hit the water. While bycatch may seem like an accidental practice, there is nothing accidental about it. Bycatch is taken into consideration for the economics of the fisheries, knowing that their current practices are causing those species not targeted to be caught and unnecessarily killed. The damage this does is apparent, as aquatic species and their populations dwindle.

photo of sea turtle
Figure 3 – Sea Turtle

For instance, while no fisheries in the world actually target sea turtles, 6 out of 7 sea turtle species have been categorized as threatened or endangered. This is not due to climate change or ocean pollution, but because of fishing practices. About 1,000 sea turtle deaths occur each year due to plastics, while in the United States alone, approximately 250,000 are captured and/or killed each year by fishing vessels.

However, the damage done by overfishing goes beyond our aquatic ecosystems. Billions of people worldwide rely on fish for a food source and as their livelihood. For instance, here in Canada, we are surrounded by the Arctic, Atlantic, and Pacific Oceans, and our lands are filled with nearly 32,000 lakes. As such, it is no surprise that one of Canada’s largest food export and employment sectors includes fish and seafood. Exports are a major part of Canada’s fishing industry, with a majority going to the United States, but also to China, Japan, and parts of Europe. In 2018, Canada exported about $6.9 billion in fish and seafood to about 140 countries. As such, the fishing and seafood industry is a crucial sector of Canada’s economy, working as a major economic driver for both coastal rural communities and major urban centres.

red and white boat on dock under cloudy sky
Figure 4 – Fishing Boats

Approximately 72,000 people are employed in Canada’s fishing industry, primarily in harvesting, aquaculture, or processing. Employment in these areas can be found across the country, except for Alberta and Yukon. The highest rate of employment for the sector can be found in Nova Scotia with over 17,669 workers, and another 17,904 can be found in Newfoundland. This illustrates how crucial the fishing industry is to Canada, and especially for provinces such as Nova Scotia and Newfoundland, where the livelihoods of many rely on it.

So, what would happen if one of these provinces began overfishing? Well, it has actually happened before, and it wasn’t pretty. In July 1992, the federal government placed a ban on cod fishing along Canada’s east coast, putting nearly 5 centuries of cod fishing in Newfoundland and Labrador on hold. Cod had played a central role in the province’s economy and culture in the past, but even today, the cod population remains too low to support a full-scale fishery.

Figure 5 – Fishing Industry

Alternatively, in 1975, the province had 15,000 fishers and 110 fish processing plants, and just 5 years later, it had 35,000 fishers and 175 processing plants. By 1992, the spawning stock of northern cod had fallen to just 1% of its estimated population, and in response, the Fisheries and Oceans minister announced a 2-year moratorium for cod fishing. Later on, the government extended the ban with no end date in sight, only making exemptions for a small stewardship fishery. This moratorium caused the largest layoff in Canadian history, affecting over 40,000 fishers and related workers. In Newfoundland and Labrador alone, nearly 30,000 people lost their jobs.

To combat this, the government introduced the Northern Cod Adjustment & Recovery Program (NCARP) throughout which workers received employment insurance payments and retraining. However, most viewed this as inadequate, causing the province’s population to drop by 10% in the first decade of the ban, as people left the province to find work elsewhere. Unable to pursue cod, the fishing industry eventually turned to shellfish – particularly snow crab and lobster. This was able to offset some of the financial impacts of overfishing the cod, but the province’s fishing industry has never managed to recover quite the same. In 2008, scientists recorded the first substantial increase in cod since 1992, and in 2015 research was published suggesting northern cod may finally be making enough of a recovery to end this moratorium. However, between 2017 and 2018, the stock made another significant drop, declining by about 30%.

photo of shark underwater
Figure 6 – Shark

In addition to employment and economic losses as a result of overfishing, there are some serious ecological losses that are likely to occur. For instance, there is growing evidence that the increased volume of commercial fishing activities is having detrimental effects on the health of our oceans as a whole. When a species that is considered ‘commercially valuable’ is overexploited, the other species and habitat within the same ecosystem are impacted. For example, let’s say we overfished a large species of shark. Overfishing this apex predator is likely to cause a ripple effect within the shark’s natural ecosystem, and consequently its food chain. With these changes could come an increase in other species, such as sting rays, as they are usually prey for larger sharks; but with fewer large sharks around, the ray populations are growing exponentially. However, since there are now more sting rays, the stock of smaller fish and shellfish that are favoured by the rays, will begin to dwindle as well. This is just one way in which overfishing can irreparably change the makeup of an ecosystem.


Every element in an ecosystem depends on every other element, whether directly or indirectly. The smallest change can make the biggest difference; a change in the temperature of an ecosystem can impact what crops can grow, or whether a species can survive. When human activities such as overfishing occur, we are forcing these ecosystems and their inhabitants to readjust and try to adapt to these changes, otherwise, they will be forced to find a new habitat, or be left to wither away. Unfortunately, this is how many species end up becoming threatened or endangered.

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