Maya Ellison
Plastic pollution is a pressing issue that affects marine life in numerous ways. Sharks, in particular, face various threats from plastic waste in the ocean. While the exact number of shark deaths caused by plastic is unknown, it is estimated that 100 million sharks die each year from entanglement in commercial shipping nets. In addition to physical harm, plastic ingestion can lead to toxic buildup in sharks, impacting their health, behaviour, and overall well-being. With plastic pollution on the rise, the survival of shark species is increasingly at risk.
| Characteristics | Values |
|---|---|
| Number of sharks that die from plastic each year | 100 million |
| Number of sharks that die from entanglement in commercial shipping nets each year | 100 million |
| Number of sharks that die from ingestion of plastic | Not a significant threat to sharks, but there are several hundred recorded instances |
| Number of sharks that die from ingestion of microplastics | Not known, but microplastics are a direct threat to life |
| Number of sharks that die from plastic pollution | 100,000 annually |
| Number of sharks that die from entanglement in plastic | Thousands |
| Number of sharks that die from entanglement in ghost nets | 9 reef sharks found in two ghost nets |
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What You'll Learn
Sharks ingest plastic, mistaking it for food
Sharks are apex predators, meaning they are at the top of the marine food chain. As a result, they are particularly vulnerable to the accumulation of plastics and associated toxins in their bodies. While direct ingestion of plastic is not a significant threat to sharks, as they can invert their stomachs to expel inedible substances, plastics can enter their systems through the consumption of prey that have already ingested plastic.
Sharks often ingest plastic debris, mistaking it for food. This ingestion can lead to serious health issues, including internal injuries, intestinal blockages, and starvation. Smaller pieces of plastic can also be inhaled through the gills or become lodged in the body, causing irreparable damage to vital bodily systems.
The plastics that sharks ingest can release toxic chemicals, which accumulate in their bodies and lead to long-term health problems. Studies have found microplastics in the stomachs of several shark species, including tiger sharks and whale sharks. These microplastics, often less than five millimeters in size, are particularly harmful as they can carry harmful pollutants that bioaccumulate in the sharks' tissues. Over time, this accumulation of toxins can affect the sharks' growth, reproduction, and overall health.
In addition to the direct harm caused by ingesting plastic, sharks can also suffer indirect harm through the disruption of their food sources. Plastic pollution can degrade coral reefs, seagrass beds, and mangroves, which serve as critical nurseries for many shark species. This pollution reduces the suitability of these habitats for supporting young sharks and can lead to lower survival rates for shark pups.
While the impact of plastic ingestion on shark health is not yet fully understood, it is clear that plastic pollution poses a serious threat to shark populations. Reducing plastic pollution requires concerted efforts at the individual, community, and governmental levels, including reducing plastic use, improving waste management, participating in clean-up initiatives, and supporting scientific research.
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Plastic nets and twine can entangle and strangle sharks
While plastic pollution is not the biggest threat to sharks, it is a significant problem that is often overlooked. The issue of plastic nets and twine entangling and strangling sharks is a serious one, with several hundred recorded instances of shark deaths caused by drifting nets or plastic waste. The actual number is likely far higher, as some estimates suggest that 100 million sharks are hunted by humans annually.
Sharks can become entangled in plastic loops of debris, making it difficult for them to swim, catch food, or escape predators. In some cases, entanglement in plastic nets or twine can lead to drowning or slow, painful deaths as the plastic cuts into their flesh. For example, a shortfin mako shark was photographed with a fishing rope entangled around it, resulting in scoliosis of the spine. Similarly, a sandbar shark in Winyah Bay, South Carolina, was found badly entangled in plastic packaging twine, slowly being sliced in half.
Plastic fishing nets are a significant contributor to the problem, whether through bycatch (the unintended capture of marine mammals like sharks) or ghost nets—abandoned fishing nets left in the ocean or on shorelines. It is estimated that 640,000 tons of ghost fishing equipment, including nets, make up part of the 8 million tons of plastic entering our oceans annually. These ghost nets silently kill sharks, fish, and other marine life worldwide, entangling them and damaging coral reefs.
The issue of plastic nets and twine entangling and strangling sharks is not a new one, but as plastic pollution in our oceans continues to build up, the rate of entanglement will only increase. This growing problem highlights the importance of reducing plastic waste and transitioning to more sustainable fishing practices to protect shark populations and the marine ecosystem they help maintain.
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Plastic debris can cause scoliosis in sharks
While plastic pollution is not the biggest threat to sharks, it is a significant ocean problem that affects the health and survival of these animals. There are several hundred recorded instances of shark deaths caused by plastic waste, with entanglement in plastic debris being a major concern. Sharks can become entangled in plastic loops, making it difficult for them to swim, catch prey, or escape predators. This can lead to drowning or severe trauma, resulting in abnormal anatomical development.
One tragic example is the case of a shortfin mako shark that became entangled in a fishing rope. As the shark continued to grow, the rope dug into its flesh, causing scoliosis in its spine. The shark also suffered from deep abrasions and undernourishment due to the prolonged entanglement. While plastic entanglements are not considered a primary threat to shark populations, they do raise significant animal welfare concerns due to the grievous wounds inflicted on these creatures.
Another way plastic debris can impact sharks is through ingestion. Sharks may mistake plastic for food, leading to the consumption of plastic debris. This issue is particularly relevant for filter-feeding shark species, which feed by straining large quantities of water and food through their gills. As a result, they may inadvertently ingest plastic-associated toxins, such as heavy metals and phthalates. These toxins can alter hormones that regulate growth, development, metabolism, and reproductive functions.
While direct ingestion of plastic may not be as harmful to sharks as entanglement, it can still have detrimental effects. Microplastics, which are plastic particles less than five millimeters in length, are a significant concern for filter-feeding shark species. These tiny plastic fragments can be ingested by sharks at the ocean's surface, where ocean currents often transport them. Ingestion of microplastics can release toxins into the shark's body, posing a direct threat to their health.
The impact of plastic debris on shark health and survival underscores the importance of addressing plastic pollution in our oceans. While it is challenging to determine precisely how many sharks die from plastic annually, the number is likely much higher than recorded. Reducing plastic waste and transitioning away from single-use plastics are crucial steps toward mitigating the harmful effects of plastic pollution on shark populations and the marine ecosystem as a whole.
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Plastic waste enters the food chain and is consumed by sharks
Plastic waste is a significant concern for marine life, including sharks. While plastic pollution is not the biggest threat to sharks—overfishing and bycatch are far more detrimental—it is a growing problem that can no longer be overlooked.
Plastics in the ocean break down into smaller pieces, known as microplastics, through exposure to sunlight and seawater. These microplastics can be ingested by marine animals, including sharks, in various ways. One way is through direct ingestion, where sharks mistake plastic debris for their prey. For example, sea turtles often consume plastic sheeting and plastic bags, which resemble their natural prey, jellyfish. Another way plastics enter the food chain is through the consumption of contaminated prey. Sharks, as apex predators, feed on other species at lower trophic levels. If a fish lower in the food chain has consumed microplastics, there is a significant chance that a shark consuming it will absorb those contaminants.
The ingestion of plastics can lead to health issues and even death in sharks. The plastic debris can get stuck in their digestive systems, causing a feeling of fullness and leading to starvation. Additionally, plastics can release toxins that accumulate in the body and disrupt hormones regulating growth, development, metabolism, and reproductive functions. Furthermore, sharp plastic fragments can cause severe injuries to the stomach and intestinal mucosa through chafing.
While direct ingestion of plastics may not be a significant threat to sharks, as they can invert their stomachs to expel inedible substances, the indirect consumption of plastics through the food chain is a concern. As plastics break down into smaller microplastics, they can be ingested by smaller species, which are then consumed by sharks, leading to the accumulation of plastics and toxins in their bodies.
The impact of plastic waste on shark populations is challenging to quantify, and further research is needed to understand the full extent of the problem. However, it is clear that plastic pollution is a significant issue that requires urgent attention to protect shark species and the marine ecosystem they help maintain.
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Toxins from plastics can alter shark hormones
While it is difficult to estimate exactly how many sharks die from plastic each year, it is clear that plastic pollution is a significant threat to shark populations. One of the main ways plastics can harm sharks is through the ingestion of microplastics, which release toxins that can alter shark hormones.
Sharks are apex predators, meaning their primary food source is dependent on prey that consume other species at lower levels of the food chain. As a result, sharks are particularly susceptible to bioaccumulation. Small fish feed on zooplankton, and larger fish feed on smaller fish, allowing microplastics to move up the food chain and accumulate in the bodies of larger fish and sharks.
Microplastics act as vectors of toxins because they absorb toxic additives and chemicals and release them into a shark's body. These toxins can lead to toxicological effects such as decreased fitness and overall health. In addition, microplastics may contain chemical additives that, when absorbed by a shark's body, can act as endocrine disruptors. Endocrine-disrupting chemicals can interfere with hormonal balance and signaling systems, potentially influencing shark behaviour.
The impact of microplastics on sharks may be amplified by climate change, which causes a rise in sea temperatures and changes in ocean currents, affecting the distribution and abundance of prey species that sharks rely on. This may lead sharks to search for food in different areas, potentially increasing their exposure to microplastics. Additionally, extreme weather conditions and storm surges associated with climate change can enhance the plastic weathering process, releasing more microplastics into the marine environment and increasing the likelihood of sharks encountering and ingesting these particles.
While the direct ingestion of plastic is not considered a significant threat to sharks, as they can invert their stomachs to release inedible substances, microplastics can still have detrimental effects on their health and well-being. Studies have shown that microplastics can contribute to the global decline in fish populations, with an estimated 100,000 deaths annually due to plastic pollution.
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Frequently asked questions
It is difficult to estimate how many sharks die from ingesting plastic as it is not the biggest threat to sharks. However, a study found that 0.38% of 28,687 large sharks caught between 1978 and 2000 had ingested plastic debris.
There have been several hundred recorded instances of shark deaths from getting caught in plastic waste, with one study counting over 1,000 documented instances. However, the actual number is likely much higher.
Plastic threatens sharks in several ways. Sharks can ingest plastic, which releases toxins that alter their hormones and regulate growth, metabolism, and reproductive functions. Sharks can also become entangled in plastic, making it difficult to swim, catch food, or avoid predators, leading to drowning.
