A 50-year study of sharks off the coast of North Carolina found that many species have decreased in size over time.
Researchers started collecting data on 12 species of sharks in 1972 in Onslow Bay, just east of Jacksonville. A recently published study analyzing this data found all 12 species appeared physically smaller over the years. Declines in maximum sizes ranged from 10% for silky sharks to 35% for sandbar sharks.
There are many theories as to why the sharks are smaller, but none have been proven yet.
Joel Fodrie is an ecologist at UNC-Chapel Hill. He says it’s still unclear exactly why the sharks have gotten smaller, but commercial and recreational fishing may be a contributing factor.
“Because people catch some of the biggest individuals and even target big individuals, you're immediately going to pull those out of the population,” Fodrie said. “So if that was the only thing happening, you might see smaller average sizes.”
Fodrie added that this combination of fewer and smaller sharks has likely contributed to shifts in local ecosystems.
"People have shown that if you lose the big sharks… the turtles can get out of hand and they can eat all the grass. And that grass is really valuable,” Fodrie said. “So you don't necessarily want a world where you got a lot of turtles and no sharks. You have to maintain that balance."
Data also found that most species had decreased in population over time.
Fodrie says researchers will continue to gather data on these sharks.