LONG BEACH (CBSLA) — A groundbreaking new study found decreasing shark populations in a number of areas — largely due to overfishing and climate change — though the California shark population was said to be thriving.
“This was a huge, huge endeavor,” Chris Lowe, director of the Cal State Long Beach Shark Lab, said.
In the most comprehensive study done on the world’s shark population, scientists spent four years gathering 15,000 hours of video data on nearly 400 ecosystems in 58 countries. To do the study, scientists dropped a cage equipped with bait on one end and a camera at the other onto the ocean floor for an hour at a time to see how many sharks showed up.
“Because they did it over multiple years, they were able to document changes in shark populations over time at all these locations,” Lowe said.
The study found that some regions in the world appeared to not have any sharks at all, with researchers unable to observe sharks in 20% of the areas they studied. The study said that shark populations have decreased in places where they get caught up in commercial fishing nets or are actively hunted for their fins — considered a delicacy in Asia. The scientists also said climate change was a factor in their disappearance from areas with food supplies shifting.
“They are really important to keep certain populations healthy,” Lowe said.
The historic research also provided some hope that conservation measures actually work. In areas where destructive fishing practices were banned, the shark population was considered healthy.
“There are tools that work, like green protected areas we know can work,” Lowe said. “Banning the use of gillnets in certain areas, we know can work. Regulating fisheries and managing them better, we know can work.”
And, Lowe said, California is one of the places where the shark population was thriving.
“California has done a really good job, I think, of managing many of its fisheries,” Lowe said. “We’ve seen shark populations decline back in the 60s through the mid-90s and then through a series of better fisheries management practices, we’ve been able to better protect many of the populations that were being harvested.”
Lowe also said sharks were mobile and adaptable, so with some focused effort, it is possible to revive their populations in areas where their numbers have decreased.