You rarely see a cookiecutter shark in action. Instead, you’ll spot the unique circular marks it leaves behind—small holes that look like they’ve been cut with a cookie cutter. Researchers have had to do some clever detective work to piece together the behavior of these elusive sharks.
A recent study from the University of Hawaii at Manoa, published in Marine Ecology Progress Series, focused on cookiecutter shark bites and sightings. The team gathered data from fisheries in Hawaiian waters, revealing important patterns in where and when these bites occur. This is the largest investigation so far, offering valuable insights for both scientists and the fishing industry.
Meet the Cookiecutter Shark
Cookiecutter sharks (Isistius brasiliensis) are relatively small, usually growing to about 20 inches. Their most distinctive feature is their unique teeth: a combination of small, upright teeth on the top and jagged ones below. They use these teeth to bite out circular sections of larger fish and even mammals like whales and dolphins.
Here’s a quirky fact: unlike most sharks, cookiecutter sharks shed all their teeth at once and eat them afterward. This behavior likely helps maintain their calcium levels.
Although cookiecutter sharks generally don’t pose a threat to humans, they can disrupt fishing, particularly for longline fisheries in Hawaii. They have also had occasional run-ins with submarines and other ocean gear.
Understanding the Bites
The new study examined reports of cookiecutter damage from 2011 to 2023. It built on earlier work that linked their activity to moon phases, using environmental data like sea temperature and salinity to model their behavior.
Findings suggest that cookiecutter bites are more common at night, especially during the new Moon when it’s darkest. Fishers tend to have longer operations during these times, making interactions with the sharks more likely. Surprisingly, the sharks prefer to target swordfish at night but go after bigeye tuna during the daytime.
A Dive into History
The researchers also looked at Polynesian records, discovering that local fishers had long been aware of cookiecutter bites. This historical context suggests that these sharks have been a part of Hawaiian waters for centuries.
Donald R. Kobayashi, an oceanographer involved in the study, noted, “These creatures have resisted formal study due to their elusive nature. It’s rewarding to contribute to our understanding of them.”
The cookiecutter shark is currently listed as “Least Concern” by the IUCN. However, experts warn that increased fishing could threaten shark populations in the future.
As we learn more about cookiecutter sharks, their role in the ecosystem becomes clearer. These fascinating creatures, with their strange biting habits and distinct marks, remind us how much we still have to discover about life in the ocean.
For more on marine life, check out the National Oceanic and Atmospheric Administration’s site on ocean ecosystems.
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Marine biology,Sharks
