Do 11,000 sharks die every hour? – More or Less: Behind the Stats

Introduction: The 100 Million Figure and Its Origins

The podcast opens with a challenge to a stat circulating in conservation circles: are about 11,000 sharks killed every hour, totaling around 100 million per year? Dr. Boris Worm confirms that this annual mortality figure is in fact consistent with global estimates, though he stresses it is an estimate with a wide margin of error. This section establishes the scope of the problem: sharks comprise more than 500 species, many of which are not the target of fisheries but are caught as bycatch or discarded after capture.

"The annual mortality of sharks that we estimate globally is at least 100 million sharks, or about 11,000 sharks every hour." - Dr. Boris Worm, Professor of Marine Conservation, Dalhousie University

Data Challenges: Coastal vs Open Ocean Mortality

The researchers distinguish between sharks killed near coastlines and those captured in the open ocean. Coastal data are more readily available but still underreported by a factor of three to four, requiring country-by-country reconstruction from catch records and expert interviews. In the open ocean, data are patchier, so the team uses a grid-based approach and machine learning to extrapolate deaths in unsampled zones. The discussion underscores how hard it is to count sharks, given the wide size range and the prevalence of bycatch records that group sharks with other elasmobranchs.

Bycatch, Size, and Survival: Untangling the Numbers

Because shark weights vary dramatically, translating catch data into numbers of individuals requires additional assumptions about size. Bycatch retention and survival rates further complicate the estimate; some sharks die after being discarded, while others are kept for meat or other products. The team integrates several data sources to calibrate these proportions, acknowledging that much of the data come with uncertainties that propagate into the final estimate.

Finning Policy, Market Dynamics, and Mortality Trends

A key policy shift—finning bans in many jurisdictions—has changed incentives for the fishery. Boris Worm explains that although finning has become less common, fisheries are motivated to retain and market whole sharks, which can sustain or even increase mortality through new demand for shark meat and other products. This nuanced effect demonstrates how conservation measures can interact with market economics in unexpected ways, sometimes offsetting gains from policy alone.

"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 fisheries from taking 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." - Dr. Boris Worm, Professor of Marine Conservation, Dalhousie University

Uncertainty, Confidence, and What It Means for Conservation

Despite the large magnitude of the estimate, Worm emphasizes the wide margins of error and the difficulty of interpreting a single global number. The research triangulates multiple methods, including expert interviews, trend comparisons, and cross-checks with regional observations, to build confidence that the broad estimate captures the scale of mortality even if the precise figure remains debatable. The takeaway is pragmatic: while 100 million is plausible, the true number could be tens of millions higher or lower, and policy impact depends on understanding where and how most deaths occur.

Conclusion: What the Numbers Tell Us About Shark Conservation

In the closing moments, the discussion reflects on the broader implications for conservation. The team notes that while outlawing finning has reduced a particularly wasteful practice, total shark mortality continues due to ongoing bycatch and new market forces. The phrase "Market economics really can have a nasty bite" captures the tension between policy progress and persistent pressures on shark populations. The episode ends with an invitation to scrutinize statistics and report suspicious figures, underscoring the value of careful, expert-driven analysis in informing conservation strategies.