In September 1996, a crew tagged and released a healthy blue marlin off the coast of Venezuela: 513 days later, the same fish was recaptured off Sierra Leone, Africa, more than 3,000 miles away. Thanks to that little tag riding shotgun on the marlin's back, scientists gleaned a greater knowledge of how far these creatures roam.
Nearly everything we know about the movements of billfish and tuna comes from a small piece of nylon commonly referred to as a spaghetti tag. Before anglers started placing tags in released billfish, scientists couldn't determine where exactly these migratory animals swam, where they spawned or how quickly they grew. We now know much more about marlin and tuna thanks to conventional tagging, but there is still plenty to learn.
Frank Mather pioneered the first tagging program in 1954 and opened the Cooperative Tagging Center (CTC), originally based out of the Woods Hole Oceanographic Institution in Massachusetts. Mather laid the groundwork for tagging programs around the world. He developed tags using a slender, stainless-steel anchor and a piece of vinyl tubing that carried the name of the tagging agency and contact information to return the tag. Anglers used these tags until 1981 when a nylon barbed dart tag replaced the original.
Mather developed the CTC to gather basic information on the movements and biology of migratory fish in the Atlantic Ocean and its adjoining seas. At first, the program primarily targeted bluefin tuna; swordfish, blue marlin, white marlin, sailfish and yellowfin tuna were added a few years later. The tagging program always relied on recreational anglers to do the majority of the tagging, and since its inception, fishermen have deployed more than 313,000 CTC tags in the Atlantic.
"If you whittle down the tagging database to include only pelagic tunas, billfish and swordfish, we have 203,461 tags deployed since 1954," says Derke Snodgrass, a fishery biologist at the National Marine Fishery Service's Southeast Fisheries Science Center, which took over the CTC in 1980.
CTC numbers do not reflect the number of fish tagged by The Billfish Foundation, which is now the largest tagging agency in the world and the only organization that actively tags billfish in all the major oceans. Peter Chaibongsai, TBF's director of science and policy, says TBF members have tagged 160,000 billfish since the program began in the 1990s.
Recapture Rates
The only way researchers can learn anything from the tags deployed is to catch that same fish and return the tag to the agency it came from. Then the scientists can see how far the fish traveled while at large and how much it grew. It's a numbers game, and although everyone who tags hopes to see one of their fish recovered some day, the odds are not in their favor.
Billfish, especially blue marlin, have a historically low recapture rate, so the more fish we tag, the better the chance of a recapture. Even with five major billfish tagging programs around the world, the overall recovery percentage for all billfish species averages just 1.3 percent. TBF holds the highest recovery rate for blue marlin at just more than 2 percent. With so few tags coming back, every one returned represents a treasure-trove of information. And unfortunately, the number of anglers and captains actively tagging fish is on the decline.
"We've seen a significant drop-off since the beginning of the millennium," Chaibongsai says. "We're looking at new ways to incorporate anglers and captains and get them re-energized about tagging. We need to highlight the need for tagging and make sure people are aware of it."
All tagging programs rely on anglers, and through the years scientists have fostered tight relationships with fishermen of all sorts. These friendships help researchers learn about the fish and the anglers who pursue them. "There are all kinds of benefits to working with recreational fishermen," says Dr. Eric Prince, chief of the Migratory Fishery Biology branch of the Southeast Fisheries Science Center. "I've really worked with the best captains and crews in the business. These guys hold detailed information on these animals that are so hard to study." But for some reason, the amount of people tagging has steadily fallen since the late 1990s.
Because so few tags come back, many anglers harbor the misconception that they don't work. The truth is that conventional tags do work, and they're probably the most cost-efficient way to study migratory fish. The main problem is that migratory fish swim in very big oceans. A few other drawbacks and challenges make studying these elusive fish even more difficult.
First off, longliners recapture the vast majority of tagged billfish. And more often than not, these tags go unreported. "I know they don't return tags," says Prince. "You can't estimate the nonreporting accurately. Some longliners fear that if they cooperate, it will push them out of business."
Foreign boats also recover a good amount of tags and don't return them to the States. "I was talking to a longline captain in Venezuela, and I held up a tag and asked him if he'd ever seen one on a fish," Prince says. "He said, 'Oh yeah, we get them fairly regularly.' I asked him what he does with them, and he told me that his wife uses the recovered tags to roll up her hair in a bun. You can see there really is a need for better communication, especially where English is not the native language."
Over the years, the CTC has printed signs in Spanish explaining how to return the data and even offered cash rewards for returned tags, but coming up with federal funds for such a program is no easy feat. The best way to get more tag returns is to spend time with the folks most likely to tag fish and recover tags. TBF really excels when it comes to outreach in this arena. And its efforts appear to be working.
TBF started shipping tags to Kenya, Asia, the Maldives, Thailand, Oman and the Seychelles, areas where it hoped to get more information. "With a small amount of money, we can reach out to those locations where we get minimal info," Chaibongsai says.
TBF also strives to make it easier to send back tag info. "For the past year or two, we've included our e-mail address on tags," Chaibongsai says. "Previously, the only way they could contact us was by telephone or snail mail. We wanted to come up with another avenue. I honestly think it's working. We saw the recapture rate increase."
Besides helping in the quest for information on billfish, anglers benefit from tagging in other ways. Each year TBF hands out release and tagging awards to captains and anglers at a posh banquet. This recognition is a great boon for up-and-coming and veteran captains alike. The International Commission for the Conservation of Atlantic Tunas also supports a lottery for all recaptured tags and gives out a $500 prize to whomever wins. But perhaps the best way to get people fired up about tagging again is to quell the fallacies about the program. Don't believe those who say tags hurt or kill fish, or that tagging leads to too much time on the wire and worn-out fish. If done properly, conventional tagging should not hurt the fish.
Proper Tagging Procedures
The tagging process and the equipment used have evolved greatly since the 1950s. The tags themselves underwent a few changes over the years, and the current version staves off algae growth and infection while remaining firmly embedded in the fish. The standard tag consists of a nylon double-barbed anchor with a nylon or monofilament trace that displays the contact information of the tag agency. But it's not the tag so much as how it's placed in the fish that really matters. While some people might profess that conventional tags kill fish, a multitude of studies show the exact opposite. A properly placed tag will do nothing to slow a fish down. However, a poorly tagged animal is another story.
"A lot of TV shows and magazines get it wrong," says fishery biologist Eric Orbesen. "You don't want to be stabbing at the fish with a 12-foot tag pole. You really need to have the fish under control, not thrashing."
Trying to get a perfect tag shot in a head-shaking blue marlin is no easy task. And many captains made the move away from tagging because they don't want to take the time to do it correctly, especially in tournament situations. With a little practice, however, a crew can master the art of tagging in very little time.
Tag placement remains the most important factor in whether a fish will swim away unharmed. Take your time and embed the tag in the muscle above the fish's lateral line away from its head, gills, eyes and other vital organs. Try to place the tag as close to the dorsal spines as possible. When placed here, the small wound will heal quickly and minimize any chance of injury. The use of a snooter around the fish's bill helps the crew control the fish next to the boat during the tagging process and revive the fish before release. If a sailfish can swim for 12 years without a tag affecting it in any way, and they have, it's a safe bet that they don't do much harm.
The next vital step that many crews glaze over is taking a quick measurement of the fish. To speed up the process, use a floating tape measure to get a measurement. Lots of crews put a tennis ball or lure at one end of a tape measure to get it to pull out straight in the water. If you can't measure the fish for some reason, take an educated guess and include that information on the tag card that accompanies the actual tag. Make sure to include an estimated weight, the location of the fish, the species, date, and the names of the angler, mate and captain. Any missing information on the card renders that tag virtually useless.
"We need those tag cards to come in legible with all info filled in," says TBF's Elliot Stark. "We'll get cards with no location, no date and no species, just the angler's name and the captain's name. That's essentially a lost tag. If it's recaptured, there's nothing we can do."
The information on the tag card plays a critical role, and it's best to fill the cards out immediately after a catch so you don't forget to do it or find yourself trying to guess how big the fish was at the end of the day or where exactly you were when you caught it. TBF actually started a program called Tag Your It to get people to fill in their cards legibly and correctly. Each week, TBF pulls a random card, and if all the information is filled in clearly and correctly, that person receives a handsome prize.
"The data is only as good as the people sending it to us," says Orbesen, who works with the CTC. "We're always finding typos in our database that we try to correct and proof."
