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Do Shark Sanctuaries Work?

One of the many ways that conservationists are trying to tackle the massive declines in shark populations world-wide, is to set up areas where any and all sharks are protected completely from fishing. These are known as "shark sanctuaries". The idea is that sharks can have a stronghold in these areas, where their populations can bolster themselves, whilst they are being extracted in fisheries elsewhere. Yet shark sanctuaries have been criticised as a conservation strategy... But why is this? Do shark sanctuaries actually work? How are they contributing to shark conservation and how might they be improved?

Blacktip reef sharks benefit from a shark santucary in French Polynesia (Image Credit: Damsea / Shutterstock)

Shark Sanctuaries of the World

There are currently 18 countries (the majority in the tropical Pacific) which have declared their entire Exclusive Economic Zone (EEZ) to be a shark sanctuary. The first of these was the Republic of Palau in 2009 (To learn more, you can check out The World's 1st Sanctuary). The primary objective of all of these shark sanctuaries is to ban commercial shark fishing (and finning) within their waters. Many also prohibit the commercial sale and import/export of shark fins, meat and curios within the country, in order to limit their contribution to the global trade in shark products (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

Shark sanctuaries have been introduced across a wide range of social and economic settings, ranging from areas of high population density to extremely remote regions, and from low GDP, developing nations to areas of high wealth. They have also been implemented for a range of different reasons; some nations citing concerns over ecosystem health, others hoping to improve their tourism industry. Some nations legislated for a shark sanctuary whilst their shark populations were still thriving, in the hopes of maintaining their ecosystem health, whilst others have introduced legislation in the hopes of boosting decimated shark stocks. Every shark sanctuary is unique (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

In 2020, Colombia also declared they planned to implement a shark sanctuary in their waters. To learn more you can check out Hail Columbia!

Yet, that may be the problem... As there is not one internationally agreed-upon standard which must be met for a site to be called a 'sanctuary', each country differs in its regulations and goals for their sanctuary. These inconsistencies have lead to the criticism of shark sanctuaries and many have questioned the efficacy of the strategy for shark conservation for several different reasons...

Some shark sanctuaries also protect their close relatives, where other sanctuaries do not specify whether similar animals enjoy the same protection as sharks (Image Credit: Stingrays in Bora Bora - Ethan Daniels / Shutterstock)

Does a Shark Sanctuary Distract from other Threats?

Many critics have cited concerns that the implementation of a shark sanctuary can distract from other significant threats which sharks face. Because sharks are not just vulnerable to fisheries! When we compare the top threats to sharks within and outside the confines of shark sanctuaries, it become clear that minimising fishing might not be enough to ensure shark conservation. Research shows that, whilst targeted shark fishing and "bycatch" (when sharks are killed in fisheries targeting other commercially valuable species) are reduced overall in shark sanctuaries (shown with ★ on the diagram), the innumerable other threats, including climate change-related ocean acidification, sea-level rise and high water temperatures, as well as incidental mortality in "ghost fishing" gear, are still a problem even within the sanctuaries. Therefore, the implementation of a sanctuary could mistakenly make people believe sharks are completely safe from harm in that area, when in reality, they are still vulnerable to many risks (Ward-Paige & Worm, 2017).

To learn more about how ghost fishing gear and other marine debris affects sharks, you can check out Ghosts in the Ocean and The Worst... Beware of The Plastics!.

Yet, in many sanctuaries, bycatch of sharks is still a significant problem. For example, in Honduras and the Maldives, the legislation for their sanctuaries does not include any details about what must be done with sharks incidentally caught as bycatch. Furthermore, many nations (including the Bahamas and French Polynesia) do not specify any fishing gear restrictions within the sanctuary, which might help to reduce the number of sharks caught as bycatch. So, just because a country has declared that no targeted fishing is allowed, this does not mean that sharks are completely safe from fisheries in all shark sanctuaries (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

Threatened scalloped hammerhead sharks are protected in the Marine Protected Area around the Cocos Islands, Costa Rica, but the area is not designated as a shark sanctuary (Image Credit: EDGAR PHOTOSAPIENS / Shutterstock)

Are Sharks Adequately Protected within the Sanctuary?

Confounding this problem is the issue of actually enforcing sanctuary laws. There has been a lot of concern that some shark sanctuaries are not sufficiently protected from poachers and therefore do not aid in shark conservation. It is not difficult to understand how challenging patrolling a shark sanctuary can be, when you consider the size of the area... even the smallest shark sanctuary, located in St. Maarten is 1,066 square kilometres, and the largest, in French Polynesia, is a whopping 4,771,088 square kilometres! It is simply an enormous task to watch every corner of these waters. Whatsmore, as many shark sanctuaries are located within developing nations, the amount of investment into surveillance can be very limited (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

Similarly, how the law is enforced and the penalties for breaches varies massively between countries. For instance, in the British Virgin Islands monetary fines "will not exceed $1,000 USD", but in the Federated States of Micronesia, these penalties can be as much as $250,000 USD! Shark poaching might still be a financially viable option if fines are low, especially for the most vulnerable members of society, who rely on shark fishing for their livelihoods or subsistence. This can mean local communities do not feel incentivised to abide by new conservation laws (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

Whilst designated as a shark sanctuary, there are no fishing gear restrictions stipulated in the Bahamas, causing some people to question the efficacy of the sanctuary (Image Credit: nurse sharks - Kim / WikimediaCommons)

How Do You Assess if a Shark Sanctuary is a Success?

Another major problem with shark sanctuaries, is that it can be very challenging to actually measure whether they are working. This is because we often do not have any "baseline" data for the size of shark populations before extraction began, so we don't know their natural abundance. The legislation for the sanctuary can also be problematic here. The majority of countries (excluding only the Caribbean Netherlands and the Republic of Palau) do not require any monitoring of shark populations within the sanctuary or do not demand reporting of shark landings in fisheries operating within the sanctuary. Subsequently, we have no way to determine whether shark populations are rising or declining since the implementation of the sanctuary and no way to evaulate the success of the sanctuary as a conservation strategy (Ward-Paige, 2017; Ward-Paige & Worm, 2017).

In the Cook Islands the legislation does not specify that any monitoring must be completed to assess whether the shark sanctuary is effective (Image Credit: grey reef sharks - USFWS - Pacific Region / WikimediaCommons)

Do Shark Sanctuaries Actually Increase Shark Abundance?

However, one way we can assess how sharks are doing within a sanctuary is to start taking data on shark abundance now and compare this with counts of sharks from other places. For example, recently scientists and volunteer divers investigated how the populations of sharks vary between different sanctuaries around the world. Divers counted the maximum number of individuals of any one species present at once (called "relative abundance") and also how many different species of sharks were present around the divers at any one time (this is known as the "species richness"). This allowed them to compare how shark numbers compared between sanctuaries (Ward-Paige & Worm, 2017).

They found that sharks were most abundant in the sanctuaries in French Polynesia, Palau and the Maldives, but relatively unabundant in the Cayman Islands and Caribbean Netherlands. Shark species richness was also highest in Palau and The Maldives, and also in New Caledonia. Species richness was low in the Caribbean Netherlands, and in Grenada and the Cook Islands. Overall though, the researchers found that shark sanctuaries supported a larger relative abundance of sharks! Good news!

The scientists stated that the wide variations in abundance and species richness might not necessarily mean certain sanctuaries are failing though! Sharks are very slow to re-establish themselves after population declines and it can take many years for their populations to increase back to healthy level. As shark sanctuaries have only been introduced recently (many less than 10 years ago), these findings might not necessarily show us how effective or ineffective each individual sanctuary might be in the future (Ward-Paige & Worm, 2017).

What is great about this research thought is that it gives us baseline data with which to assess sharks populations in the coming years. If we recreate this work a few years down the line, we will be able to evaluate whether sharks populations are growing equally in each sanctuary, and thus, decide how we need to tweak the legislation, in order to improve the efficacy of each sanctuary (Ward-Paige & Worm, 2017).

Even so, it still seems quite likely that, whilst shark sanctuaries do have their benefits, they are not going to be powerful enough to bolster shark populations on a global scale. Sanctuaries currently only cover 3% of the Earth's oceans and therefore, sharks are still extremely vulnerable to innumerable threats when they are outside of the sanctuaries. The scientists who conducted this study stated that for shark sanctuaries to be effective, they would need to operate alongside many other management measures put in place to protect sharks when they wander into other waters, including: strict monitoring of and limitations on trade, bans on targeting endangered species, protection of critical habitats, mitigating against the treats of climate change, and reducing extraction in fisheries down to sustainable levels... Basically, sharks should be safe from extinction throughout every single part of our oceans, not just in one corner, where a sanctuary is located.

"[Shark sanctuaries as a] conservation strategy [are] likely not sufficient in isolation & require added conservation measures"

- Ward-Paige & Worm, 2017

The shark sanctuary in the Dutch Caribbean does not enforce fines or other penalties for breaches of the law, causing some to wonder whether people will respect the protected area (Image Credit: Albert Kok / WikimediaCommons)


Ward-Paige CA (2017). A global overview of shark sanctuary regulations and their impact on shark fisheries. Marine Policy, 82, 87–97. Access online.

Ward-Paige CA & Worm B (2017). Global evaluation of shark sanctuaries. Global Environmental Change, 47, 174-189. Access online.

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