Do 11,000 sharks die every hour?

Summary

Podcast Summary: More or Less: Behind the Stats

Episode: Do 11,000 sharks die every hour?

Host: Lizzie McNeil (BBC Radio 4)
Guest: Dr. Boris Worm, Professor in Marine Conservation, Dalhousie University
Date: September 6, 2025

---

Main Theme

This episode investigates the startling statistic that 11,000 sharks die every hour—a claim circulating in marine conservation circles and newsletters. Host Lizzie McNeil speaks with marine conservation specialist Dr. Boris Worm, whose research is the basis for the 100 million sharks-per-year figure, to unpack the methodology, uncertainties, and real-world impact behind this headline number.

---

Key Discussion Points & Insights

Sharks’ Public Image Versus Reality

• Popular culture, especially Hollywood, paints sharks as fearsome predators, but the episode quickly subverts this stereotype, focusing instead on the human threat to sharks.
  • "Imagine a fishy cinema, a school of sharks cowering as the young shark family on screen are mercilessly caught in man made nets..." (01:50, Lizzie McNeil)

The 100 Million Sharks Estimate

• Dr. Boris Worm confirms the annual global mortality estimate is at least 100 million sharks (02:51).
  • Quote: "Yes, it's true that the annual mortality of sharks that we estimate globally is at least 100 million sharks, or about 11,000 sharks every hour. So that's a lot." (02:51, Dr. Boris Worm)

Shark Biodiversity & Victimhood

• Over 500 shark species, ranging from tiny thumb-sized sharks to massive whale sharks (03:29, Dr. Worm).
• Most sharks aren’t hunted on purpose—they are largely victims of bycatch in fisheries targeting other species.
  • Quote: "In most cases, actually, they're being caught as bycatch. We're not intending to kill them, but unfortunately we do by fishing for other things." (03:56, Dr. Boris Worm)

Conservation Status

• Of 500+ species, 31% are threatened and 6.5% critically endangered (04:04, Lizzie McNeil).

How the Statistics Were Calculated

Coastal Fisheries

• Data available but highly variable in quality. Official figures severely underreport catches; reconstructions using old records, interviews, and expert input were necessary (05:01-05:18, Dr. Worm).

Open-Ocean (High Seas) Fisheries

• Data even more limited, so Boris’s team divided the oceans into a grid and used machine learning to extrapolate figures (05:18, Lizzie McNeil).

Other Layers of Uncertainty

• Bycatch survival rates: Had to estimate which sharks sold, discarded, and survived (05:57, Dr. Worm).

• Catch data often reported by weight, requiring estimation of average shark size to convert to number of individuals (06:19, Lizzie McNeil).

• Some catch data lump sharks with other species (elasmobranchs): estimates have to be made to isolate shark numbers (06:50, Dr. Worm).

• Quote: "...those numbers are underestimate by a factor of three or four. So we had to go country by country and reconstruct from old catch records and interviews and expert data to estimate the missing sharks, if you will." (05:01, Dr. Boris Worm)

• Quote: "It was very hard to resolve what proportion of those bulk reported elasmobranch fishes are actually sharks. So that's just one source of error." (06:50, Dr. Boris Worm)

Wide Margin of Error

• The estimate could range from 60 to 270 million per year, but 100 million is the most plausible central figure from latest research (07:21, Dr. Worm).

  • Quote: "Yeah. So it's really hard to say what the margin of error is... I think from our latest paper, I would think that the range is a little lower, but it could be in the order of a couple hundred million sharks." (07:21, Dr. Boris Worm)

• Validation: Their analysis lined up well with field experts’ observations (07:54, Dr. Worm).

  • Quote: "We did a bunch of expert interviews... and it matched up near perfectly. So that gave us a lot of confidence..." (07:54, Dr. Boris Worm)

Fishing Industry Impact & Exploitation Rate

• Fishing kills 6–7% of the entire shark population each year (08:38, Dr. Worm).
  • Quote: "In a previous study we estimated that 6 to 7% of all sharks that live in the sea are being killed every year." (08:38, Dr. Boris Worm)

Conservation Efforts and Unintended Consequences

• Shark finning (removal of fins for soup/medicine) has been outlawed in many places and has reduced, a success for campaigns (09:21, Dr. Worm).

  • "That practice had been outlawed in a lot of jurisdiction... has become much less common, which is a real success." (09:21, Dr. Worm)

• But: Laws preventing finning shifted markets to whole shark products (meat, cartilage, oil), arguably increasing demand and possibly mortality (09:21-10:05, Dr. Worm).

• Quote: "In some ways there was even incentive to keep the whole shark and develop these new markets, which increases the value, which increases the demand. This might have caused this spike in shark mortality that we did not anticipate and did not want." (09:21, Dr. Boris Worm)

---

Memorable Moments & Notable Quotes

• "Are these numbers fishy or is it true that this many sharks are being killed?" (02:16, Lizzie McNeil)
• "They're mostly not being hunted on purpose... In most cases, actually, they're being caught as bycatch." (03:47-03:56, Dr. Boris Worm)
• "A lot of these sharks are caught accidentally and some are thrown back into the ocean by the fishers." (05:18, Lizzie McNeil)
• "So maybe 100 million sharks are being killed a year, give or take tens of millions of sharks." (08:23, Lizzie McNeil)

---

Timestamps for Important Segments

• 01:38–02:51: Introduction to the shark mortality statistic and listener question
• 02:51–03:02: Dr. Boris Worm confirms statistic
• 03:12–03:47: Shark species overview & threat analysis
• 04:04–05:18: Shark conservation status and mortality calculation for coastal fisheries
• 05:18–07:00: High seas data challenges, estimation methods, and further uncertainties
• 07:21–07:54: Discussion of error margins and validation methods
• 08:38–09:21: Exploitation rate; effectiveness of shark finning bans
• 09:21–10:05: Economic incentives lead to new shark product markets and possibly greater shark mortality

---

Conclusion

The claim that 11,000 sharks die every hour is grounded in the best available global research, though it is a rough estimate with potentially huge margins of error due to incomplete and unreliable data. Most sharks aren’t intentionally targeted but end up as bycatch, and while bans on finning have changed practices, they may have inadvertently increased overall shark exploitation. The big picture is clear: human fishing activity continues to pose a grave threat to global shark populations.

---

If you spot a suspicious stat, email: moreorlessbc.co.uk

---

Transcript

[Lizzie McNeil]

This BBC podcast is supported by ads outside the uk. You can make a difference in someone's life, including your own, with a job in home care. These jobs offer flexible schedules, health care, retirement options and free training. They also provide paid time off and opportunities for overtime. The Visit OregonHomeCareJobs.com to learn more and apply. That's OregonHomeCareJobs.com.

[GoDaddy Advertiser]

Running a business online look legit and own your own brand with professional tools from GoDaddy instantly build trust with your customers and boost your credibility with an email that matches your domain so people know you mean business. There's never been a better time. Just go to GoDaddy.com GDnow and choose from a wide variety of popular domains to find one that's right for you. Pair that with a professional email that works for all your business needs, from daily communications to email marketing and everything in between. That's a little price for a lot of credibility. For a limited time, get a domain and matching professional email for just 99 cents a month for one year. Go to GoDaddy.comGdNow and look legit with GoDaddy. That's GoDaddy.comGdNow again GoDaddy.comGdNow there's never been a better time to choose the domain and email that's right for you. New customer purchases only products Auto renew separately. See terms on site godaddy.com gdnow.

[Lizzie McNeil]

Hello and thanks for downloading the More or less podcast. We're the program that looks at the numbers in the news, life and under the sea. And I'm Lizzie McNeil. Thanks to certain Hollywood stereotypes, sharks have something of a scary image problem. But what if the films have got it wrong and it's actually the sharks who should be scared of us? Imagine a fishy cinema, a school of sharks cowering as the young shark family on screen are mercilessly caught in man made nets and fishing trawlers. And they've the right to be afraid. Many sharks are killed this way each year. The question is though, how many loyal listener and steward got in touch to ask about a stat she saw in a newsletter from marine conservation charity Sea Shepherd Global. And the email claimed that every hour 11,000 sharks are killed. That's over 100 million every year caught in nets, hunted for fins or discarded as bycatch. Those sound like very big and surprisingly round numbers. So are these numbers fishy or is it true that this many sharks are being killed?

[Dr. Boris Worm]

Yes, it's true that the annual mortality of sharks that we estimate globally is at least 100 million sharks, or about 11,000 sharks every hour. So that's a lot.

[Lizzie McNeil]

This is Dr. Boris Worm, a professor in marine conservation at Dalhousie University in Canada. His research is the source of this claim.

[Dr. Boris Worm]

Unfortunately, it's more than that very ancient group of species can sustain.

[Lizzie McNeil]

Now, before we start explaining how he worked this number out, you need to know something about sharks. Loads of them are the complete opposite of massive and terrifying.

[Dr. Boris Worm]

There's over 500 species of sharks from very large. Actually, the largest fish in the world is the whale shark to some very tiny ones that are about the size of my thumb and everything in between. And we mostly think about the largest, say, hammerheads or blue sharks, bull sharks, white sharks and so on.

[Lizzie McNeil]

They are also mostly not being hunted on purpose. Instead, they're getting caught in nets and lines used to hunt other fish.

[Dr. Boris Worm]

In most cases, actually, they're being caught as bycatch. We're not intending to kill them, but unfortunately we do by fishing for other things.

[Lizzie McNeil]

Now, there's no doubt that fishing has put many species of shark at risk. Of those 500 plus types of shark, there are 31% are threatened and 6.5% are critically endangered. Sharks are being killed in very large numbers by industrial fishing fleets and fishermen and women all around the world. But how did Boris work out this figure of 100 million for the total shark death toll?

[Dr. Boris Worm]

So we did a variety of global analyses to derive that number. We separated shark mortality to those that live in coastal waters and those that live far from shore on the high seas.

[Lizzie McNeil]

These two data sets posed quite different problems to Boris and his team. For the coastal fisheries, governments do publish data on the quantities of sharks that are caught in the waters, though the quality of this data is highly variable.

[Dr. Boris Worm]

We knew how many sharks were reported to be killed by those countries, but those numbers are underestimate by a factor of three or four. So we had to go country by country and reconstruct from old catch records and interviews and expert data to estimate the missing sharks, if you will.

[Lizzie McNeil]

At least there's some actual data from these coastal fisheries. For the open ocean away from land, the data is even worse. So Boris divided these waters into a grid and used a machine learning system to extrapolate figures for the sharks killed in each zone using the patchy data at his disposal. So it's fair to say that this is not a precise number. And on top of all of this uncertainty, we can add a bit more. First, as we said, a lot of these sharks are caught accidentally and some are thrown back into the ocean by the fishes.

[Dr. Boris Worm]

And that bycatch is a problem because a lot of those sharks don't survive. So we also had to estimate the proportion of sharks that, when they get caught, get retained and sold or thrown back in the water. And then of those, what proportion survives? And we used all available studies that people have done to get at those proportions in the most accurate way we possibly could.

[Lizzie McNeil]

What's more, much of the data comes in the form of the weight of the shark that's being killed. But because sharks come in a massive range of sizes, including lots of tiddly little sharks that no one thinks about, you've got to make more estimates about the size of the sharks being killed to work out the numbers of sharks per ton. On top of this, some of the catch data doesn't record sharks, but only a grouping called elasmobranch, which includes sawfish, skates, rays as well as sharks.

[Dr. Boris Worm]

So it was very hard to resolve what proportion of those bulk reported alazenbranch fishes are actually sharks. So that's just one source of error.

[Lizzie McNeil]

They use this data, where the sharks were identified, to work out what proportion of the elasmobranc might be sharks. And that makes up 20 million of the hundred million figure. So if you have unreliable government data, combined with reconstructed missing data, combined with estimates on top of estimates.

[Dr. Boris Worm]

Yeah. So it's really hard to say what the margin of error is. In this paper, we didn't provide a range of numbers that could be plausible. In a previous paper, we estimate that, that the range was between 60 and 270 million sharks killed every year. I think from our latest paper, I would think that the range is a little lower, but it could be in the order of a couple hundred million sharks.

[Lizzie McNeil]

Boris is very clear that the estimate is an estimate. Sharks are hard to count.

[Dr. Boris Worm]

We did a bunch of expert interviews to back up our analyses and to see whether the trends that we were seeing in the data were matched up by what people who had a lot of knowledge about, about particular geographies we're seeing on the ground. And then we put all of that together and it matched up near perfectly. So that gave us a lot of confidence that what people are seeing on the ground, who are visiting markets, who know about fishing communities, who are tracking entire fleets, is similar to what we found in our global analysis.

[Lizzie McNeil]

So maybe 100 million sharks are being killed a year, give or take tens of millions of sharks. Either way, it seems the international fishing industry is taking a sizable chunk out of the shark population every year.

[Dr. Boris Worm]

In a previous study we estimated that 6 to 7% of all sharks that live in the sea are being killed every year. So that's the rate of exploitation which we measured three different ways just to be sure that it's correct and I think it's in that ballpark.

[Lizzie McNeil]

A major purpose of Boris's research was to work out whether international efforts to protect shark populations had actually worked to lower the number numbers being killed. Much of this has focused on the practice of so called finning, which is a horrifically wasteful practice where a shark's fins are cut off for use in shark fin soup and traditional medicine and the rest of the shark, often still alive, is discarded back into the sea.

[Dr. Boris Worm]

That practice had been outlawed in a lot of jurisdiction and according to our data and our expert interviews, has become much less common, which is a real success. Unfortunately, it did not prevent fishers from taking and fishing and retaining sharks because they were just not allowed to cut the fins off and sell them separately. So they had to retain the whole sharks and find markets for shark meat, shark cartilage, shark liver oil and other products. And so in some ways there was even incentive to keep the horse shark in develop these new markets, which increases the value, which increases the demand. This might have caused this spike in shark mortality that we did not anticipate and did not want.

[Lizzie McNeil]

Market economics really can have a nasty bite. All in all, you can think of 100 million as a plausible estimate, albeit one with a wide margin of error. Just in case you thought it was safe for sharks to be back in the water. Our thanks to Dr. Boris Worm. And that is all we have time for this week. If you see any suspicious stats, please do let us know at more or lessbc.co.uk until next week, goodbye.

[Brooke Gladstone]

This is the story of the 1. As head of maintenance at a concert hall, he knows the show must always go on. That's why he works behind the scenes, ensuring every light is working, the H Vac is humming and his facility shines with Grainger's supplies and solutions for every challenge he faces. Plus 24. 7 customer support. His venue never misses a beat. Call quickgranger.com or just stop by Grainger for the ones who get it done. There's a lot going on right now. Mounting economic inequality, threats to democracy, environmental disaster, the source of stench of chaos in the air. I'm Brooke Gladstone, host of WNYC's on the Media. Want to understand the reasons and the meanings of the narratives that led us here and maybe how to head them off at the pass. That's on the media's specialty. Take a listen wherever you get your podcasts.