On Monday, a group of anglers from Texas, Colorado, and California hooked a colossal fish off Southern California. After a long struggle, they reeled in a shortfin mako shark that they say tipped the scale at 1,323.5 pounds (600 kilograms).

The shark is 11 feet (3.3 meters) long and 8 feet (2.4 meters) in diameter, Kent Williams, a certified weight master at New Fishall Bait Company in Gardena, California, told the Los Angeles Times. The massive mako was caught by a team of professional hunters and fishers who produce reality television for the Outdoor Channel. The three-day, deep-sea excursion was being filmed for the show Jim Shockey's The Professionals, a program that aims to document the lives of Outdoor Channel crew.

The anglers are storing their catch in a deep-freeze locker in Gardena, and they are applying for a world record from the International Game Fish Association. The certification process is expected to take around two months, because the fishing group needs time to analyze the specimen and tackle used and to interview eyewitnesses.

The previous record holder for a mako was a 1,221-pound (554-kilogram) catch made in July 2001 off the coast of Chatham, Massachusetts.

Corey Knowlton, a co-host of The Professionals and an expedition guide, told National Geographic that the team had spent 30 to 40 days on the water over the past four years looking for a big mako to take. A few days ago, Knowlton and the other anglers had been trying their luck about 15 miles (24 kilometers) off Huntington Beach, by dropping chopped mackerel and ground chum into the water.

They were rewarded with the sight of fins slicing the water, so they tossed out giant hooks. One took, and the team spent two and a half hours of "struggling, slipping, and sliding" to bring in the creature, according to published reports.

"They fight really hard, it was a very aggressive predator," said Knowlton. "It was trying to eat the birds and everything around it. It took the bait immediately and ran, ran, ran."

Knowlton added that the big fish jumped out of the water five times. "When it first jumped we all screamed, we were going crazy," he said.

Crew member Jason Johnston, who lives in Mesquite, Texas, climbed into a harness to work the fish. He described the scene to the Times as "mayhem" and "the scariest thing I've ever done in my life."

Knowlton said the group had caught several makos up to 900 pounds (408 kilograms) over the past few years, but their goal had been to catch something over 1,000 pounds (454 kilograms), to have something sizable to donate to science. "They haven't had one this big. So we were really, really excited to finally see it, it was a giant behemoth."

Knowlton said Mary Blasius at the University of California, Long Beach, is excited to examine the specimen, and that the team has also reached out to the National Oceanic and Atmospheric Administration (NOAA). A mold is also being made.

Mako Science

Suzanne Kohin, a shark biologist at the NOAA lab in La Jolla, California, told National Geographic that her agency has been in touch with the anglers about the shark. "Samples will be valuable to us, because we have a hard time accessing these large individuals," she said.

"We prefer to tag and release them, to study their movement patterns, but it is useful to sample. We may learn something about its reproductive status or foraging ecology," she added. (Related: "100 Million Sharks Killed Every Year.")

Kohin said the mako is most likely a female because males rarely reach a size bigger than 600 pounds (272 kilograms). She said it is likely over 15 years old, although testing is needed to confirm. Kohin added that shortfin makos are relatively common off Southern California, where females often give birth to pups in a "nursery."

"It is very rare for us to find these large makos—although of anyone, recreational fishers are the ones to catch them," said Kohin. She added that government surveys tend to use smaller hooks, and such large sharks may be powerful enough to bite through commercial drift nets or wriggle off longlines.

Makos tend to stay out in the open ocean, feasting on small fish like mackerel and sardines, so they rarely interact with people. They are among the fastest of all sharks. Fishermen routinely catch makos up to six feet (two meters) long.

The fishermen have pointed out that their big catch left them well within their legal state limit of two makos a day. But that doesn't mean their success hasn't touched a nerve in the conservation community.

Conservationists Speak Out

Marine biologist, author, and advocate Carl Safina told National Geographic that he still loves the excitement of fishing for makos, although he switched to catch and release around 15 years ago.

"I think we should be long past the point where killing such a creature should be talked about so breathlessly, using words like 'historic' and other hype," said Safina. "It doesn't 'make history' for the animal involved, it ends it."

Voicing similar concern, ocean advocate and author David Helvarg of Blue Frontier Campaign said, "If someone just claimed the record for shooting the largest elephant ever shot in Africa, people would be appalled. Apparently too many people haven't made that connection with endangered top predator 'game fish.'"

Helvarg added that people have fished out an estimated 90 percent of the ocean's largest fish, and there are indications that some fish species are genetically downsizing in response to that pressure. "CPR—catch, photograph, and release—might have stressed this monster of the deep, but it also would have left it to breed and feed and also left us with a sense of awe and respect knowing it was still out there," said Helvarg.

The shortfin mako is not on the endangered species list, but the species is considered "vulnerable" by the International Union for Conservation of Nature (IUCN). According to Kohin, not much is known about the mako's population status off California. "We don't know if it is in trouble or not," she said, adding that scientists hope to work on a survey in 2014.

The most recent federal regulation, the Pacific Council's Highly Migratory Species Fishery Management Plan, allows for a total of 150 metric tons of mako to be harvested a year by a combination of commercial and recreational interests, Kohin said. According to a 2010 report, the estimated average catch of both the commercial and recreational fisheries combined for the prior five years (2005-2009) was 53 metric tons, well below the 150-metric-ton harvest guideline, although there is uncertainty in the catch estimates, particularly the recreational numbers.

Still, Kohin said, "Removing a reproductive-age female is not a good idea. With any shark that is late to mature and produces few pups, they are much more vulnerable." She said makos don't reach maturity until ages 8 to 15 years, older than many other species in the area.

Defending his team's catch, Knowlton said, "There have been studies that say those sharks are on the increase. We never have any trouble finding sharks, some days we see eight or 10 or more, so there are a lot out there."

To Safina, killing any sharks at a time when they face intense global pressure from the fin trade and death as bycatch in commercial fisheries sends the wrong message to people, many of whom still view sharks as brainless killers. "Whether killing one very, very successful individual giant animal will harm the population isn't the whole issue," he said.

Echoing Safina's concern, Amanda Keledjian, a marine scientist with the group Oceana, said, "There might be a few old sharks out there but in general the larger body of evidence suggests that so many thousands are caught as bycatch off California every year. That's the bigger concern."

Keledjian added, "A lot of recreational fisheries are thought to have a small impact but that's not always the case, and sometimes they don't have the same accountability or don't have to report how much they catch. If it remains unknown it can be problematic for managers trying to set science-based limits."

Catch and Release?

Laleh Mohajerani, a National Geographic grantee who heads the board of Pescadores y Tiburones, a group that promotes shark conservation in Mexico's Baja California, said she was saddened to hear of the death of such a large marine animal.

"We are fishing out all the large species, so when you see an animal that is that remarkable and had such amazing survival to make it that big, you feel, why was it not released?" asked Mohajerani. "It's like if we were to discover a dinosaur and then kill it because we wanted to hunt it.

"Some people say 'they are not endangered,' 'we don't fish that many,' and all these other excuses," Mohajerani continued. "But IUCN says they are vulnerable, so we have to err on the side of caution."

Mohajerani added that many sportfishers care about the environment, and she pointed to growing interest in catch and release methods, especially when it comes to slow-reproducing fish like sharks.

For his part, Knowlton said, "We really care about these animals. We realize there is no old folks' home for sharks. That shark is going to die and no one is going to know anything about it. By going out there and taking the animal, getting it to a freezing facility, getting it to the correct people, that is getting the most out of this animal."

Knowlton added that being able to analyze the fish's brain and other parts may provide insight into mercury and other toxin accumulation. He said the same data would not have been available if the group had released it. He added that the boat's captain, Matt Potter, had tagged and released many sharks over the years, starting when he was a teenager.

Perhaps putting it more bluntly, Kent Williams, who weighed the mako, told the Los Angeles Times, "It's all part of the food chain. If they were endangered, they wouldn't allow us to fish them."