Research reveals drop in shark population

Junette Reyes/Staff Writer

There is no need to fear Jaws when you head to the beach — at least fear a little less as the shark population around the world is on the decline.

The effect of a declining shark population will not only affect the survival of shark species, but can also cause consequences to ecosystems, the environment and human populations.

An average of one million shark deaths was reported in 2000 and 2010 by executive director of the School of Environment, Arts and Society Michael Heithaus in a paper titled “Global Catches, Exploitation Rates and Rebuilding Options” published in the journal “Marine Policy.”

“What we tried to do was figure out how many sharks worldwide were being killed in fisheries every year,” Heithaus said. “There’s a fairly big range. It could be the high 60 million up to more than 200 million.”

The mortality rate was compared to the rate of reproduction among shark populations which showed that more sharks are being caught than reproduced annually.

“If we look at what other people have done around the world, looking at the catches of sharks in commercial fisheries, we see that shark populations over the last several decades have dropped a huge amount, in some cases 80 percent or even more,” Heithaus said.

That research, Heithaus said, proves that there is a valid necessity to fix the problem, not only because catching rates exceed reproduction rates when shark populations are already dangerously low, but because of how the decline in shark populations can affect their surrounding environments.

“We are really concerned about this decline and continued overfishing of sharks because it might disrupt whole marine ecosystems,” Heithaus said. “There is work that my colleagues, students and I have been doing in Australia for many years that shows that having tiger sharks in seagrass ecosystems is really important for the seagrass itself because they kind of keep the grazers in check.”

Heithaus suggested that the concern can even shift to the fish and fisheries people rely on.

“If we lose sharks and seagrass ecosystems are disrupted, then there might not be the habitat that shrimp and fish grow up in. We’d see less fish making it in the fisheries for people,” he said.

As for solutions to the problem, Heithaus said one approach is to lessen the high demand and value of shark fins, such as taxing the exportation and importation of shark fins. Heithaus said that early reports suggest that this is starting to happen in the Chinese government, where the serving of shark fin soup is being discontinued in official functions.

Another approach is to have better international regulation and enforcement.

“Sharks that stick around the coast of places like the U.S., where we have strong fishery laws and enforcement, they can do ok, but a lot of sharks go out into the open seas and international waters,” Heithaus said.

He said that in order to regulate the catches, especially for species of sharks that are worse off than others, both international agreements and limitations on international trade need to be set.

“It’s just not worth it for people to catch them,” said Heithaus.

junette.reyes@fiusm.com