The National Wildlife Federation

Donate Donate

Hooked on Billfish

Marlin, sailfish and spearfish are among the most magnificent creatures in the sea, but commercial fishing has driven down their populations; now a simple change in fishhooks may help save them

  • Roger Di Silvestro
  • Feb 01, 2009

SPORTFISHING FOR MARLIN and sailfish off the U.S. Atlantic Coast is a $2-billion-a-year industry. Competitive tournaments, such as one held annually in Ocean City, Maryland, can yield top winners more than $1 million in prize money. Countless recreational anglers take to the seas yearly, trolling baits for hours, even days, in the hope that a marlin or sailfish will engage in battle.

Sportfishers usually release their catches. In the Ocean City tournament in 2008, for example, 300 boats caught 349 white and 23 blue marlin, of which a total of 19 were brought to shore dead. But billfish—as marlin, sailfish and their kin are collectively known—and the sport industry dependent on them, do face a grave threat: commercial longline fishing, in which boats put out monofilament lines up to 60 miles long with baited hooks suspended about every 100 feet. Longlining has helped reduce Atlantic marlin populations by as much as 90 percent in recent decades.

No Fish Tale:

The biggest billfish ever caught on rod and reel was a blue marlin, landed off Kona, Hawaii, in 1973, that weighed 1,805 pounds.

Ironically, marlin generally are not targeted by the pelagic (open-ocean) longline industry. Fisheries biologists estimate that about 70 percent of billfish caught in the Atlantic are bycatch—fish caught incidental to landing targeted species such as tuna. Strangely enough, the one billfish species that is commonly targeted—the swordfish—is doing relatively well, according to John Graves, a biologist at the Virginia Institute of Marine Science who has studied marlin and other billfish since 1990. For example, North Atlantic swordfish populations have almost fully recovered from lows in the 1990s, thanks to catch reductions and good spawning conditions. However, a potential solution to the decline of nontarget billfish may already be showing positive results, says Eric Prince, the biologist who heads up the National Oceanic and Atmospheric Administration’s (NOAA) billfish research in the Atlantic.

Ten species of billfish swim the world’s seas. Blue marlin and sailfish occur worldwide. The white marlin is limited to the Atlantic, and black and striped marlin to the Indian and Pacific Oceans. Of four species of spearfish, two are found only in the Atlantic, one in the Pacific and one in the Mediterranean Sea. The tenth billfish species is the swordfish, which belongs in a distinct family of its own and is found in oceans worldwide.

In swordfish, blue marlin and black marlin, males tend to max out at about 300 to 350 pounds, though Robert Humphreys, a NOAA fisheries biologist who has studied billfish for 15 years, says some may reach 500. Females, however, may comfortably exceed 1,000 pounds; maximum sizes remain unknown. “It would surprise no one if one exceeded 2,000 pounds,” Prince says. Other billfish are smaller. Striped marlin rarely reach 500 pounds, and white marlin and sailfish rarely exceed 200; spearfish usually weigh well under 100 pounds.

Scientists know little about billfish life histories. “We’re still working to better determine age and growth, longevity and age at maturation,” says Humpreys, adding that billfish rank among the ocean’s most elusive creatures. “It is extremely hard to get a handle on them,” he says. They are challenging to locate as adults, and species are difficult to find and identify as eggs and larvae. Prince agrees. “Billfish don’t school in the traditional sense of the word, so you don’t get a lot of information on them at one time,” he says. “There is no place you can go and be sure of catching a blue marlin.”

In his research, Humphreys has found evidence of yearly billfish spawning off Hawaii’s Kona Coast. “The early life history is pretty spotty,” he says, but it appears that spawning is restricted to warm surface waters of at least 75 degrees F. Although swordfish eggs raised in 73- to 75-degree-F water hatch within 65 hours of fertilization, marlin, spearfish and sailfish probably hatch within 24 hours, Prince says.

After most billfish species reach about 4 or 5 inches long, Prince says, they become very hard to catch, swimming too fast to be caught in the nets scientists typically use. They tend to remain out of reach of humankind until about a year old and perhaps 4 to 6 feet long. As the fish grow, they presumably expand their range, Humphreys says, with bigger fish roaming more widely—even thousands of miles. Atlantic swordfish inhabiting colder waters in the northern extent of their range are primarily big females, which probably are feeding on large squid and on fish such as snake mackerel and deepwater snappers at depths down to 2,600 feet.

Fact Finding

Gathering data needed for billfish management is as difficult as collecting information on life history. The problem, Humphreys says, is especially challenging in the Pacific, where many different nations and various management commissions with overlapping jurisdictions are trying to compile fishing data. “My take on it is that we’re playing catch-up in our efforts to assemble a more complete time series of fisheries data that will provide more accurate stock assessments,” Humphreys says. What is known is that billfish populations face immediate threats from overfishing, he says, while possible impacts from other threats, such as pollution and global warming, remain uncertain.

In the Atlantic, the picture is less complicated. The Atlantic covers a smaller area than does the Pacific, and data collected there are relatively standardized because the Atlantic is subject to only one monitoring group, the International Commission on Atlantic Tuna (ICCAT), which, despite its name, tracks population trends for various species caught on longlines.

ICCAT first identified Atlantic blue and white marlin as “overexploited” in 1992, says Prince, who chaired the ICCAT billfish working group for more than 25 years. Whites are the most overexploited of Atlantic billfish and “probably the most overexploited resource under ICCAT jurisdiction.” Sailfish are being caught in the west Atlantic at the maximum level their population can sustain and likely are overexploited in the east, he says. Blue marlin are suffering mortality four times higher than they can sustain. Remedying the situation is difficult because of the many entities that play a role in billfish ecology. However, given that the majority of mortalities are due to offshore longlining, a relatively simple change in fishing gear offers one possible solution, Prince says.

A Workable Solution

The traditional fishing hook used in pelagic longline fishing by Europeans and Americans is the J hook, familiar to anyone who has ever visited a bait shop. Asian longline fishers, who are responsible for most fishing efforts worldwide, use a Japanese-style tuna hook that looks and fishes much like a J hook. In circle hooks, the curve leading from the shank of the hook into the barb is bent more gradually, forming more of an O than a J. As a result, swallowed circle hooks do less internal damage to fish. About three-quarters of billfish that swallow J hooks are unlikely to survive, Prince says. The mortality of those that swallow circle hooks is about half that.

Because longline fishing is the biggest source of billfish mortality worldwide, “If you want to make a difference, longliners are where you do it,” says Graves, who has served for 14 years as chair of the U.S. ICCAT Advisory Committee. His research in the U.S. Atlantic coastal pelagic longline fishery suggests that circle hooks will increase the survival of bycatch species in that fishery. The United States requires all of its Atlantic longliners, and some of its Pacific fisheries, to use circle hooks, and other nations are adopting them, too. In Brazil, some longliners found that target species such as tuna were more likely to be captured alive on circle hooks and, therefore, to bring higher prices at market because the meat is fresher. “They all switched to circles; nobody had to twist their arms,” Prince says. “It was win-win. They had a financial incentive to do this.”

Circle hooks also have been adopted in sportfishing contests in the United States. About 60 to 80 percent of billfish that take bait on J hooks swallow the hooks, Prince says. The hooks can damage gills, slash stomachs and penetrate other organs. Circle hooks, however, usually impale mouth parts, particularly the corner of the jaw. About half of billfish caught recreationally on J hooks die, compared to only about 4 percent caught on circle hooks, Prince adds. Studies by Graves and his colleague Andru Horodysksy also indicate that survival of white marlin released by recreational anglers is significantly better for circle hooks than for J hooks.

Prince says that sportfishers can further reduce billfish mortality by removing hooks after capture—special, commercially available dehooking devices can enhance this process. Removing hooks helps to reduce subsequent injury or infection. He also suggests resuscitating fish that are too weak to swim away by towing them behind or alongside the boat until able to swim. Ensuring that the fish are revived helps reduce loss to sharks as well as to the side effects of exhaustion.

Ellen Peel, head of the Billfish Foundation, agrees that “the circle hook is a major step forward.” However, she adds with cautious reservation, “More needs to be done looking at critical life stages. We also need more research on the exact design of the hooks. The government has never defined it specifically.” Nevertheless, Peel says that recent data, suggesting a slight though statistically insignificant uptick in white marlin, represent the first encouraging sign in 30 years. If the trend continues, she says, “We can breathe a sigh of relief.” Assessments are done every 4 to 6 years; the next one is slated for 2010.

Humphreys suggests that in addition to circle hooks commercial fishers also should consider making other technological changes to limit bycatch. For example, he says, squid fishers in the North Pacific previously fished with surface gill nets and caught tons of fish bycatch. When recently they switched to fishing at night with bright overhead lights and squid-jigging machines, the catch converted to almost 100 percent squid. He also cautions that further data are needed on the survival of billfish released after hooking. “These are the kind of studies we need to continue to be sure we’re not fooling ourselves,” he says.

Roger Di Silvestro is a National Wildlife senior editor and book author.

Creature at Risk: The Seesaw Future of the Sawfish

The sawfish can easily be mistaken for a billfish, given its long, rapierlike snout or rostrum. But the sawfish rostrum is edged with sharp teeth, unlike that of billfish, and, to top it off, the sawfish is not even classified as a true bony fish, as billfish are. A relative of sharks, the sawfish is a type of skate or ray—more or less a shark with a flattened body.

One thing the sawfish has in common with billfish, however, is the tenuousness of its existence. Sawfish occur in warm tropical and subtropical waters around the globe. Two species of sawfish, largetooth and smalltooth, have been recognized historically in U.S. waters. The last confirmed report of a largetooth sawfish in U.S. waters occurred in the 1940s, according to John Carlson, a biologist with the National Marine Fisheries Service. Smalltooth sawfish were once prevalent throughout Florida and were commonly encountered from Texas to North Carolina. Currently, smalltooth sawfish can only be found with any regularity in South Florida, mostly in the Everglades. Based on the contraction in range and anecdotal data, it is likely that the population is currently at less than 5 percent of its size at the time of European settlement.

Adult sawfish swim in open seas and bays and even appear in rivers—they can survive in fresh water for months. Using their rostrums, they slash through schools of fish, such as mullets, and eat the pieces, or dig in the floors of seas and bays for shellfish. As babies and juveniles, however, they rely on mangroves. Born in groups of about eight live young, each about 3 feet long, they probably mature at 8 to 20 years old, Carlson says. While growing, they live in the shallow waters of mangrove stands, seeking safety from hungry sharks.

Shoreline development destroyed much mangrove habitat, and coastal fisheries also put a dent in U.S. sawfish populations. It is no coincidence, Carlson says, that sawfish have held on in South Florida, where the Everglades was made into a national park in 1947: The park is one of the few places left in the fish’s U.S. range where mangroves still thrive.

In recent years sawfish have been beleaguered by the shark-fin-soup industry and by demand for rostrums as curios and for use in cockfighting. Sawfish fins are particularly rich in the cartilage content fin eaters seek, so sawfish fins can sell for as much as $550 a pound. Cockfighters use rostrum teeth to make spurs for warrior roosters; the teeth are supposed to serve better than horn, shell, sea lion teeth, stingray spines and other pointed objects used in the rooster arms race. Spurs made from a single rostrum can be worth as much as $6,000.

In 2007, the Convention on International Trade in Endangered Species declared sawfish off-limits for international commerce, offering promise for the animal’s survival. Moreover, says Carlson, “The National Marine Fisheries Service is doing a lot of good outreach, teaching fishers how to release sawfish.” The smalltooth is protected as endangered under the U.S. Endangered Species Act. A listing proposal for the largetooth sawfish failed in 2003 partly from a lack of data. The new protections should help the surviving fish, however.—Roger Di Silvestro

Web Exclusive

So Literary a Fish

Sport fishing for sailfish is big business in Florida, as is fishing for the species’ close relatives, blue, white, black and striped marlins, wherever they occur around the world. Trolling for them has grown in popularity ever since novelist Zane Grey began writing accounts of his fishing expeditions around 1918—he helped make New Zealand a bill-fishing capital. He also is credited with being the first person ever to land with rod and reel a marlin that weighed more than 1,000 pounds, though the catch was later disqualified by the International Game Fish Association (IGFA) because the fish had been injured by sharks before it was brought to the boat.

Writer Ernest Hemingway helped increase the popularity of trolling for billfish, too, with his vivid descriptions in the 1930s of marlin hooked between Key West, Florida, and Cuba: “Then he comes out again, and the spray roars, and again, then the line feels slack and out he bursts headed across and in, then jumps wildly twice more seeming to hang high and stiff in the air before falling to throw a column of water and you can see the hook in the corner of his jaw.” Hemingway took to the sea, he said, because “great ocean currents are the last wild country there is left.” Hemingway consumed the bounty of the last wild country with enthusiasm: Writing for the New York Times, author and billfisher Paul Greenberg loosely calculated in 2007 that Hemingway landed in his lifetime about 800 marlin. Hemingway also wrote a novel about catching a blue marlin, a work that in 1953 won him a Pulitzer Prize; the following year he won the Nobel Prize in Literature.

But there was give in Hemingway’s take, too. He was one of the founders of the IGFA, created in 1939 to establish a code of ethics for sport marine anglers and their conduct at sea.

For more information on billfish and the survival challenges they face, see the National Wildlife feature “Hooked on Billfish.”

Get Involved

   Please leave this field empty

Happening Near You

You don't have to travel far to join us for an event. Attend an upcoming event with one of our regional centers or affiliates.

Learn More