A two decade-long study showed female lemon sharks returned to the place they were born to give birth to their own young.
In 1995 a research team tagged 2,000 baby sharks with tracking devices and found they returned to their birthplaces 15 years later, a Stony Brook University news release reported.
"We used each shark's individual DNA fingerprint to construct a large family tree," Doctor Kevin Feldheim, the A. Watson Armour III Manager of the Pritzker Laboratory for Molecular Systematics and Evolution at The Field Museum and the lead author of the study, said. "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."
Researchers had always suspected female sharks returned to their birthplaces, but they were never able to prove it because it is extremely difficult to track a shark from birth to motherhood without advanced technology.
"The lagoon in Bimini is almost like a lake," project founder Dr. Samuel Gruber, president and director of the Bimini Biological Field Station Foundation, said. "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."
Shark populations have been drastically declining due to overfishing. The shark's fin is the prime ingredient in a culturally important Chinese soup. The marine creatures are especially vulnerable to overfishing because they have few young at one time and long stages of development.
"The lagoon in Bimini is almost like a lake," project founder Dr. Samuel Gruber, president and director of the Bimini Biological Field Station Foundation. "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."
"When we tagged the first baby sharks in Bimini, Bill Clinton was President of the United States," Chapman said. "When they started to mature and return to give birth, Barack Obama was President. If you think of all that has happened in the world over that period, just consider that is the amount of time it takes for many large sharks to reach maturity."
