What Sharks are Endangered and What You Can Do

By AT&T Digital Media Productions editorial team

Sharks are one of the planet’s oldest species, evolving to become dominant ocean predators over 400 million years. But the last 100 years have seen the rise of threats that nature could never have anticipated. From direct overfishing and accidental by-catch to loss of habitat and destruction of ecosystems, man-made threats have landed over 70 species of shark on the IUCN’s threatened list, with more being added every year.

But if mankind is largely responsible for these threats to shark populations, we can also take responsibility for reversing these trends. Scientists and activists have made significant research and policy advances, particularly in the last 20 years. While more aggressive conservation measures are needed, there is reason to hope.


Overfishing is the top threat to shark populations

By far, overfishing is the main threat to wild populations of sharks, along with their close relatives, rays and chimaeras. While actual catches are notoriously under-reported, it’s estimated that unintentional catches alone number 50 million sharks per year, accounting for the majority of overfishing.

But with developing markets and depleted populations of more commercially desirable fish, much of this by-catch is now welcomed by consumers. The global market for shark fin soup is a well-known factor in shark depletion, and traditionally saw sharks being “finned” and thrown back into the ocean to die. But sharks are increasingly sought for their meat, with mako and thresher sharks especially prized. The livers of the deep sea, dogfish, and basking sharks are also in high demand from the pharmaceutical industry, with shark liver oil used to treat a number of conditions from acne to cancer.

Sharks tend to grow slowly and reproduce in small numbers, leaving them particularly vulnerable to overfishing. And since many sharks prefer to feed on commercially valuable species like tuna—which are themselves overfished—the risk of by-catch increases exponentially.

Most cruelly, the intentional killing of sharks due to the imagined risk that they pose to people, fishing equipment, or other species contributes to several shark species’ threatened status.


Recreational shark fishing

While commercial fishing deservedly receives the most attention, recreational shark fishing has a less studied effect. Most Sportfishing is practiced responsibly, but some fishermen still practice catch and kill techniques in their pursuit of records and trophies. This can result in the death of large pregnant females, dealing a double blow to shark populations.

Even as fishermen and tournaments adopt catch and release policies, if proper techniques are not followed, sharks may become stressed and more susceptible to death after release. Those engaging in catch and release shark fishing must be familiar with the species they encounter, and should take care to use the right equipment to prevent unnecessary deaths.


Ocean pollution

Chemical toxins such as mercury, DDT, and organochlorines have been documented in sharks close to areas of human activity. Some shark populations exhibit alarming levels of pharmaceutical compounds due to exposure from waste water discharge. Even in remote, deep-water locations, high contaminant levels have been detected in species like the Greenland shark, offering further evidence that ocean pollution knows no border. Compounding the problem is sharks’ status as apex predators, accumulating not only environmental pollutants, but the built-up toxins present in their prey.

Non-chemical pollution is another major concern. Discarded commercial fishing equipment is the biggest of these threats, but any kind of man-made refuse, such as plastic toys, can become stuck in sharks’ gills.


Shark habitat and ecosystem damage

Pollution and environmental contamination have increased significantly due to worldwide coastal development. Many shark species rely on coastal areas as a safe place for finding food, giving birth, and maturing to adulthood. Degradation of coastal habitats makes sharks especially susceptible to negative environmental changes at vulnerable life stages. 


Ocean warming and acidification

Increasingly warm and acidic seas have had profound impacts on shark populations, from behavior to food supply. Sharks can linger too long in unnaturally warm waters, with “thermal shock” causing them to miss seasonal migrations. The location of sharks’ prey is also easily affected by changes in water temperature. As fish move away from equatorial waters, sharks follow, leaving their ancestral territory behind.

Meanwhile, atmospheric carbon dioxide, caused mainly by fossil fuel consumption, is absorbed by the oceans, where the gas dissolves into carbonic acid. Elevated acidity inhibits the ability of phytoplankton and shellfish to form shells. NOAA research indicates that a decrease in these bases of the marine food chain creates a chain effect up the ecosystem, with less food available to all predators, including apex predators like sharks.


Steps in the right direction

Recent years have seen the passage of important shark protection laws. The 2011 Shark Conservation Act banned shark finning in the US, cutting back on the cruel disposal of live, finless sharks back into the ocean. Further state legislation has banned the possession, sale, trade, and distribution of shark fins, with 2013 bans in California and New York dramatically disrupting the core of America's shark fin trade.

Improvements in commercial fishing practices can also yield positive results. For example, switching from steel to nylon leaders both reduces shark by-catch and improves catch of targeted species. New “smart” hook designs, shark deterrents, and avoidance measures can also greatly reduce by-catch.

While significant policy strides have been made recently, effective shark conservation requires an increase in pace and scope. A number of university research programs conduct crucial research on humans’ ecological impact on threatened shark populations, including the University of Miami’s Shark Research Program and UC San Diego’s Scripps Institute of Oceanography. National agencies such as the NOAA and Australia’s Sharksmart initiative also yield important insight.

Ultimately, the public may have the greatest capability to protect endangered sharks, particularly when it comes to overfishing. By choosing more sustainable fish and avoiding foods and products made from sharks, consumers can reduce the economic incentive for commercial fisheries to target sharks and keep by-catch.

With funding cuts threatening scientific research of all kinds, it’s important for concerned citizens to help persuade lawmakers to draft and pass further legislation, including funding for shark research as well as proactive pollution controls. Sharks face a daunting scope of threats, and with almost all of them man-made, it’s up to humans to correct course and protect these amazing species.

Don’t miss a moment of Shark Week, only on Discovery