(CNN) -- For millions of years, sharks have been the kings of the oceans, the top of the food chain.
But these days, the hunter has become the hunted, because of better methods from commercial fishermen who are looking for fins to make expensive, exotic soup sold mostly in Asia. Shark fins are far more valuable than shark meat, so fisherman cut the fins off live fish and throw the sharks overboard to maximize the catch they bring back. Shark finning is illegal in the United States.
Another foe is tournament sport fishermen, who target and kill the biggest ones they take from the sea.
These tournaments -- dozens each year in the United States -- attract large crowds of anglers but also draw protests from animal rights groups and environmentalists.
The competitors say they are enjoying a fun, legal sport. The prizes for the largest sharks can reach $5,000 or more.
And the impact on the overall shark population is very small, one tournament organizer told CNN. Most of the sharks caught are tagged and returned to the ocean, said Dave Johnson of Kennebunkport, Maine. At the tournament he started, the rules say sharks must be a certain length to be weighed -- for instance, blue sharks must be at least 9 1/2 feet long, he said. He also said that no one ever comes close to the federal guideline of killing one shark per day during the three-month season.
"I enjoy watching these animals, but I also enjoy catching and releasing them, and very rarely killing them and eating them," he told CNN's Kaj Larsen.
"If I thought ... every five years killing one shark was endangering the species and contributing to their decline ... I'd stop doing it tomorrow."
Which is exactly what marine biologists like Luke Tipple want to happen.
"I believe that they should just stop it. Realistically, we don't need to be targeting, in any way, any of these threatened populations," he said, while giving CNN a tour of a marina in the Bahamas where shark fishing is prohibited.
Up to 73 million sharks are killed annually, and many species are at risk of extinction, Tipple said. Many of the sharks targeted by such tournaments are listed as threatened, he said.
Tipple, the managing director of the Shark-Free Marina Initiative, a project of the Humane Society of the United States, said he'd prefer that all tournaments, instead of just a few, were catch-and-release events -- if the tournaments won't end altogether.
The 32-year-old, who has been fascinated by sharks since his first encounter at the age of 5, said killing what fishing advocates call a small number of sharks harms the food chain by removing the "larger, breeding adults."
As an apex predator, sharks have a dramatic effect on keeping the marine ecosystem balanced. The repercussions of overfishing include an unbalanced food chain and damaged coral reefs. It will also make it harder to catch seafood, which, without sharks, will have more predators to worry about, he said.
He doesn't see any benefit to tournaments where big sharks are killed.
Johnson said he works with biologists who dissect the sharks to gather information on shark populations. Whatever remains of the sharks is taken to a composting area.
"They study everything from the cartilage to the liver," he said "I mean they dissect these things out completely, take samples, even do genetic analysis."
Tipple said that much is already known about sharks and there's no need to kill these animals. He also worries about the message a shark tournament sends to future generations. Sharks have more value, he said, than just as a trophy for a wall.
CNN's Kaj Larsen and Heather O'Neill contributed to this report.