Great White Sharks: How Many Are There and Why Are They at Risk?

Great white sharks are iconic marine predators that are found around the world in temperate and subtropical waters. But what threats is this species facing, and how many of these sharks are there?

Great whites (Carcharodon carcharias) can grow to lengths of more than 20 feet and weigh up to 4,500 pounds, according to the National Oceanic and Atmospheric Administration (NOAA) Fisheries.

In U.S.-waters, the range of these sharks extends from Maine to the Gulf of Mexico on the Atlantic side, and from Alaska to California and Hawaii on the Pacific side.

According to NOAA shark scientist Tobey Curtis, genetic research has shown that white sharks around the world are divided into multiple regional subpopulations.

These subpopulations include white sharks in southern Africa, Australia/New Zealand, the northeastern Pacific, the northwestern Pacific, the northwestern Atlantic, South America and the Mediterranean.

A great white shark
Stock image: A great white shark. The true number of great whites around the world is unknown. iStock

While white sharks are relatively well-studied, estimating the total global population is challenging and the true number is unknown.

"There are no global estimates of white shark population size," Curtis told Newsweek. "However, as large-bodied apex predators their numbers are naturally low compared to many other marine species."

"Population estimates have been attempted in some discrete regions such as South Africa, Australia, and off California, however, even these local estimates are highly uncertain. These estimates have generally been in the low thousands of individuals in each region," he said.

While scientists don't know the true number of great white sharks that are present around the world today, scientists have been able to monitor changes in the relative abundance of these animals in different regions where data is collected.

"Over years and decades of monitoring, we can get some idea of whether the population is trending upward or downward," Curtis said.

Great white shark populations off the U.S. Atlantic and Pacific coasts have been trending upward since federal and state regulations were put into place to protect these animals in the 1990s. In many other parts of the world, of the world, populations are trending downward, often due to overfishing.

A great white shark
Stock image: A great white shark leaping out of the water. This species is classified as "Vulnerable" by the IUCN. iStock

"The primary threat to white shark populations is overfishing," Curtis said. "While there are no longer any targeted fishing operations for white sharks, they are still accidentally caught by fishing vessels targeting other species. If this 'bycatch' is too high, it can cause populations to decline or slow recovery."

"Lesser threats include catches in beach protection programs in some areas, habitat degradation, and climate change."

The conservation status of white sharks around the world tends to be better than many other sharks and rays, according to Curtis.

"Their populations have been depleted, but not as severely as others," he said.

The International Union for Conservation of Nature (IUCN) classifies the species, which can live for more than 70 years, as "Vulnerable," which is one category away from "Endangered."

"Over three generation lengths (159 years), the white shark is estimated to be increasing in abundance in the Northeast Pacific and Indian Ocean, and declining in abundance from historic levels in the northwest Atlantic and south Pacific. In most regions, declines occurred during the 1980s followed by slow recovery since the 1990s when protection was implemented," the IUCN report on the species says.

"Globally, based on long-term abundance data and protections instigated in the 1990s that have since reduced catches and allowed some recovery, the White Shark population is estimated to have reduced by 30–49 percent over the last three generations, and is therefore assessed as Vulnerable."

Similarly, white sharks are not listed as threatened or endangered under the U.S. Endangered Species Act. According to Curtis, great whites are actually one of the best protected sharks around the world, with past conservation efforts enabling several populations to recover.