Shark moms return to their birthplaces when it’s time to have their own litter, a new study suggests.
After nearly two decades of research, scientists in the Bahamas confirmed that female lemon sharks return to the place where they were born when it is their time to give birth. The study began in 1995, when more than 2,000 baby sharks were tagged and monitored.
"We found that newborn sharks captured in the mid-1990s left the safety of the islands when they were between five and eight years old. Yet, despite leaving and visiting many other islands in their travels, these sharks remember where they were born after a decade of roving, and are able to find the island again when they are pregnant and ready to give birth," Kevin Feldheim, manager of the Pritzker Laboratory for Molecular Systematics and Evolution at the Field Museum in Chicago and the lead author of the study, said in a statement.
The study, published in the journal Molecular Ecology, is the first to prove what scientists have long speculated: that lemon sharks have the ability to find their original birthplace and return to it. Bimini island in the Bahamas proved to be the ideal spot to test the hypothesis.
“The lagoon in Bimini is almost like a lake,” project founder Samuel Gruber, president and director of the Bimini Biological Field Station Foundation, said in a statement. “I realized that we had a chance to capture nearly every shark born into the lagoon each year, and this gave us the unique opportunity to see if the females actually come back to give birth. However it took us nearly two decades and countless hours in the field and laboratory, but we finally answered this long-standing question and many others with this paper.”
The study’s results highlights the growing need to recover the world’s coastal shark populations. Rather than being wanderers, the fact that they return to the same nurseries indicates they need to be better protected.
Researchers found that female lemon sharks, which become sexually mature at 15 to 17 years, tend to return to their birthplaces every two years on average.
"We're realizing these nursery areas are really vital for these populations," Feldheim told Newsday. "There's some females that have been giving birth [in the research area] the entire course of the study."
Lemon sharks are considered a “near threatened” species on the IUCN Red List. The coastal shark is common in the Atlantic Ocean along the coasts of the United States to Brazil and possibly in some areas on the West African coast. It’s caught for both commercial and recreational reasons. Their fins also fetch a high price and their meat is consumed in the United States and in Central and South America.
But parts of the Caribbean have taken strides to stop shark hunting. In 2011, the Bahamas passed anti-poaching legislation to protect more than 40 species of shark. Palau, the Maldives and Honduras also prohibit shark hunting.