A dorsal fin breaks the surface

Two ways to count sharks

Did you pick up the July edition of National Geographic to read about great white sharks, or read the article online? (Pro tip: you should.)

The article’s author, science writer Erik Vance, contributes to a blog that I follow called The Last Word on NothingI was delighted to read a follow-up he posted to his National Geographic feature, explaining how scientists count sharks. At the heart of the method is a beautiful piece of statistics (a model) that allows scientists to draw conclusions about the size of a population – some of whom are tagged or marked  – based on only a sample of the individuals, and what proportion of those sampled individuals is tagged.

A dorsal fin breaks the surface
A dorsal fin breaks the surface

Why is it important to know how many great white sharks (or cowsharks, or whale sharks, or or or…) there are? The most obvious answer relates to conservation: if we have a baseline population estimate, we can then determine whether it is increasing or decreasing over time. What is the status of the population? Are these animals endangered, or flourishing? Are conservation measures necessary? Are they effective?

Go and read about counting sharks here. An important thing to pay attention to when you are reading any scientific model is what the underlying assumptions are, because they will show you the circumstances under which the model will fail.

And for some hot off the press South African research on a related subject but taking a different (genetic) approach, check out this press release. The study’s author, Sara Andreotti, spoke on the topic at the SA Shark and Ray Symposium in 2015.

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Clare

Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

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