Reef Grief

In 2020 we were met with a horrifying headlines in the news: "Sharks ‘functionally extinct’ from one in five coral reefs" - ScienceMag". "Reef sharks are in major decline worldwide" - BBC. "Sharks 'functionally extinct' at 20% of world's coral reefs as fishing drives global decline"- The Guardian. A new study, which had sought to assess the populations of reef sharks around the world had found startling results, and conservationists, shark scientists and the public were all left flabbergasted and appalled. So what does this study mean? What impact could this have? And can we turn it around?

Reef sharks caught on a BRUC camera (Image Credit: Janet Greenlee, Source: Global FinPrint)

Team Work Makes the Dream Work

In 2020 a massive, global study was published highlighting serious declines in reef shark populations all over the world. The study was conducted by an enormous number of shark experts, collaborating internationally. They had installed 15,000 baited remote underwater video (BRUV) stations on 371 different reefs spanning 58 countries! (MacNeil et al, 2020)

BRUVs can be used to video underwater animals in the wild with minimal disturbance (Image Credit: Andy Mann, Source: Global FinPrint)

These BRUVs recorded video footage of marine animals, which were attracted to the apparatus by bait attached to the camera frame. The scientists could then remotely observe animals in wild conditions and assess how many sharks are currently living on coral reefs. All the research teams followed the same methodology and then pooled their knowledge, to assess their respective reef shark populations, and gain some understanding about reef shark abundances globally. Quite a remarkable display of team work! (MacNeil et al, 2020)

Many of the shark scientists were quite disturbed by their findings... They learned that sharks were completely absent from 69 of the 371 reefs they surveyed (that's 1 in 5) and they concluded that reef sharks were "functionally extinct" in at least 8 countries! This means that there would be less than 0.1% chance of seeing these sharks at reefs in the Dominican Republic, the West Indies, Vietnam, Kenya and Qatar (MacNeil et al, 2020).

"There has been widespread depletion of reef sharks across much of the world’s tropical oceans"

- MacNeil et al, 2020

A global study has found that reef sharks are functionally extinct (lighter grey markings) in many regions and can now only be found on a few reefs (dark grey dots) around the world (MacNeil et al, 2020)

Missing In Action

So why have these sharks gone missing on such a broad scale? The researchers determined that there were several different socioeconomic factors which had contributed to these declines.

Sharks are critical to the health of coral reef ecosystems (Image Credit: frantisekhojdysz / Shutterstock)

For instance, countries where many people live near to the coasts had very few sharks on their reefs and comparatively, if a reef was located further away from urban centres with fish markets, sharks were more likely to be flourishing. They also found a clear relationship between poverty and reduced shark abundances. Finally, they noted that the areas with the most severe shark declines were those which either had very few fishing regulations or only poorly enforced their regulations (MacNeil et al, 2020).

The reearchers concluded that fishing sharks, especially for their fins, is responsible for the decline in sharks on reefs globally, but that areas which are particularly badly affected are those where the local population live in poverty because these communities have no choice but exploit declining populations of sharks (MacNeil et al, 2020).

A Glimmer of Hope?

But it's important to note - and what many of the alarming headlines did not emphasise - is that this study did also find some positive results (*phew*)! The scientists also learned that sharks were doing very well in many areas; such as the Maldives, French Polynesia, Australia, the Bahamas and the USA (these nations are positioned at the top of the list in the chart below). The experts determined that sharks were doing well in these counties because they have regulations in place to control the levels of shark fishing. So, the good news is, that it seems that regulations to protect shark populations DO have some positive effects in pratice (MacNeil et al, 2020).

Conservation potential of reef sharks in different countries depending on different protective methods implemented: Nations higher in the list have the highest shark abundances (shown in yellow), and at the bottom have the lowest (shown in black). Horizontal lines show the potential for shark population rebounds if measures were introduced - with shark sanctuaries and catch limits being the best methods for bolstering shark populations on coral reefs (MacNeil et al, 2020)

The scientists suggested that implimenting protective measures for sharks could have a huge impact on their numbers in the wild. They found that the nations with the highest "conservation potential" were Madagascar, Hawaii, the British West Indies and Barbados. So if legislations was implimented in these countries, they would see that their sharks should rebound (MacNeil et al, 2020).

They recommended that creating sharks sanctuaries (areas where little to no shark fishing is permitted at any time) would have the best results (see right column of chart) and that introducing a catch limit (second column from the left) would also be effective for conservation (MacNeil et al, 2020).

A global study has identified that the Bahamas, USA, The Maldives, French Polynesia and Australia all have high shark abundances (larger circles) on their reefs (MacNeil et al, 2020)

A Balancing Act

These findings are of incredible valuable because it teaches us that there is a way to turn shark declines around... it is not a lost cause!

Scientists say we can boost reef shark populations if countries implement protective legislations like catch limits and shark sanctuaries (Image Credit: frantisekhojdysz / Shutterstock)

Whatsmore, it shows us that there is a way to ensure the survival of declining shark populations, whilst also allowing local fisheries to continue to work. In many nations where sharks are depleted, the community has no option but to rely on fishing for subsistence and/or income. Therefore, it is of critical importance that scientists work together with local communities to develop conservation strategies which can create a sustainable future for everyone - punishing the poorest, most vulnerable people with fisheries closures will not be productive in the long run! If governments, scientists, law enforcement and local people can all work together towards shark conservation, there is a way that both sharks and people can flourish together!

"When governments and communities work together, they can protect their sharks. So, you can have both fishing and healthy reefs"

- Mike Heithaus, Shark Research Scientist

To learn more about how sharks are vital for the health of coral reefs, check out Restructuring the Reef.

References

MacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, Harvey E, Goetze J, Kiszka J, Bond ME, Currey-Randall LM, Speed CW, Sherman CS, Rees MJ .. Cinner JE (2020). Global status and conservation potential of reef sharks. Nature, 583. Access online.

By Sophie A. Maycock for SharkSpeak