Study shows species is going functionally extinct in some areas
A study found that reef sharks are going functionally extinct in some areas, largely due to overfishing.
Researchers collected data from 58 nations on 371 reefs.
The worldwide population of reef sharks is slowly on the decline.
A study published on July 22 in the journal Nature showed that sharks are almost completely absent from reefs in several nations.
Scientists say they are generally not a threat to humans.
Using more than 15,000 standardized, baited remote underwater video stations on 371 reefs in 58 nations, researchers observed no sharks on almost 20% of the reefs.
The study went further to investigate the reason behind the decline, and it provided concrete solutions to conserve these animals.
The problem mostly stems from humans.
“One of the major contributing factors to the decline is fishing. We already knew that, and this study definitely showed that,” Dr. Jenn Caselle, a research biologist at the UCSB Marine Science Institute, told the News-Press.
Dr. Caselle is one of 150 authors of this study. She and Darcy Bradley, co-director of the Ocean and Fisheries program at the university’s Environmental Market Solutions Lab, both contributed a vital portion of the study.
To measure abundance, researchers would watch the footage and find the single frame with the largest amount of sharks. Of those drops, 63% saw no sharks.
Dr. Caselle and Ms. Bradley collected and reported data at Palmyra Atoll, an American territory in the middle of the Pacific Ocean. Dr. Caselle described this area as a “very, very healthy, almost pristine system.”
“It was a really important endpoint for the study, because since every measure they had was relative to the other, the data would all be very similar, and you wouldn’t be able to distinguish between healthy and unhealthy ones,” Dr. Caselle said. “Our contribution was important because it provided a healthy system by which all the other systems could be compared to.”
The study, according to Dr. Caselle, was a snapshot all around the globe, and she suspects many new studies will come out of this large collaboration.
To measure shark abundance, researchers deployed cameras that Dr. Caselle said are pretty comparable to GoPros — “easy to handle and not too high-tech.”
From there, the researchers go through the entire video until they find the single frame in the video with the most number of that species in it.
Of those camera drops, 63% saw no sharks.
“The major correlation we found with places that had no sharks or very few sharks was actually proximity to a high density of humans,” Dr. Caselle said. “They’re fished for both their fins and their meat. That’s one of the biggest problems.”
She added that the study’s proposed solutions set it apart from other research.
the ocean “is not so vast that we can’t harm it.” She said shark conservation zones
and bans on destructive fishing practices will help keep reef sharks from going extinct.
“This wasn’t just another documentation of the demise of our oceans,” Dr. Caselle said. “It gave actionable advice.”
The advice was to ban or at least reduce overfishing of sharks and their prey. Specifically, the study called to lessen the use of longlines and gillnets, which the researchers classified as destructive fishing practices.
“We’re not talking about tiger sharks or blue sharks. These are the ones you might see swimming along the coral reefs that generally do not pose a threat to humans,” Dr. Caselle said.
She added the average length of reef sharks ranges from 3 feet to 7 or 8 feet.
“The best remedies are marine-protected areas or shark conservation zones,” the biologist continued. “We recognize that might not be a very acceptable solution for a lot of countries that may depend on fishing sharks for food.”
While reef sharks aren’t going extinct all over the world, Dr. Caselle said that for a community very in tune with the ocean, it’s a good reminder that “the ocean is not so vast that we can’t harm it.”
“I’ve gotten a firsthand look into what our oceans can be like,” she said. “I feel like I have this understanding of what it should look like that a lot of people don’t have, so to see some of these places maybe get back to looking like that would be really amazing.”
email: gmccormick@newspress.com
FYI
For more about sharks, go to nature.com/articles/s41586-020-2519-y. To learn more about the UCSB Marine Science Institute, visit msi.ucsb.edu.
