A new study from the Virginia Institute of Marine Science shows that shark populations along the East Coast are starting to recover after a decades-long decline.
According to the researchers, the gains are coming as a result of enactment of new fishing regulations in the early 1990s. Those regulations, designed to curb the fishing of sharks for commercial and recreational purposes, helped to halt a decline that began in earnest after the 1975 movie Jaws painted sharks as dangerous predators that needed to be killed in order to ensure the safety of beach-goers.
“We’ve shown that after over two decades of management measures, coastal shark populations are finally starting to recover and reclaim their position as top predators, or regulators of their ecosystem,” said lead author Cassidy Peterson. “Our research suggests we can begin to shift away from the era of ‘doom and gloom’ regarding shark status in the United States.”
The study combined data from six different scientific surveys conducted along the U.S. East Coast and the Gulf of Mexico between 1975 and 2014. The researchers believe it provides a more accurate outlook than other studies that were based on commercial fishery landings or surveys in one location.
Although research surveys are typically designed to remove these influencing factors, they still didn’t capture population trends as accurately as this new study. But due to sharks’ migrations and complex life cycles, often data from different surveys will conflict. The combination of data from six different studies offsets this problem.
With their method of pooling data and calculating numbers, the researchers estimated population trends for seven of the most common shark species in the region—the large-bodied sandbar, blacktip, spinner, and tiger sharks; and the smaller Atlantic sharpnose, blacknose, and bonnethead sharks.
“All the large-bodied sharks showed similar population trends, with decreasing abundance from the mid-1970s to the early 1990s, then a multi-year period of low abundance, and recent indications of recovery from past exploitation,” said Peterson.
The small coastal sharks also increased in abundance. The one exception was blacknose sharks in the Gulf of Mexico, where they are susceptible to by-catch in trawl fishing for Gulf shrimp. But even the blacknose increased in population along the Atlantic coast.
Study co-author Rob Latour, a VIMS professor, says the population trends make sense. Large-bodied sharks saw the greatest initial declines because they mature late and produce few pups, and because anglers aggressively sought them out. The smaller sharks, however, have higher growth rates and were not subject to the same fishing pressures, so their population decline was smaller and recovery quicker.
The researchers did, however, find out that there is a correlation between shark numbers and climactic patterns. With the increasing pace of climate change, shark populations will need continual monitoring to ensure that their populations don’t begin declining again.