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.

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