The science of tagging fish began with tuna decades ago, but has since evolved into a global effort for multiple species.

Tag Along

Tagging adds a fun and valuable element to any fishing trip.

Fish tags vary in size, shape and complexity, but they all benefit the greater good of the species.

Fish tags vary in size, shape and complexity, but they all benefit the greater good of the species.

Fish tagging has been around in one form or another for many decades. But it took the formation of the Cooperative Game Fish Tagging Program to organize what had been local efforts and begin the process of channeling these efforts into an international program.

The late fishery scientist Frank Mather created the Cooperative Tagging Program in 1954 at the Woods Hole Oceanographic Institute, initially to tag bluefin tuna. But Mather’s process was soon applied to billfish around the world, as more crews began tagging and releasing sailfish and marlin.

The National Marine Fisheries Service (NMFS) ran the tagging program for many years and spectacular tales of tagged fish and recaptures abound. For example, Mather once told me of a bluefin tuna tagged off Cat Cay in the Bahamas, which was recaptured only 70 days later in Norway.

On another excursion to Venezuela, Mather tagged a white marlin that everyone aboard the boat thought was dead; the fish sank from sight, motionless, with blood pouring from both gills. That fish was recaptured 18 months later. Its survival points out an obvious truth: A fish on the deck is dead for sure, but it will always have a chance of survival if you release it.

Conventional tags, sometimes called spaghetti tags, use metal or plastic darts, which get embedded in the flesh of the fish with a tag stick, typically in the “shoulder” next to its dorsal fin. A colored plastic streamer (hence the “spaghetti” moniker) attached to the dart bears a tag number and information on how to contact the right organization to report a recapture. If you catch a tagged fish, try to clip the tag off and retain it if you plan to release it.

This decidedly low-tech scientific research tool has been somewhat overshadowed by the development of high-tech satellite tags that gather a wealth of data while attached. The tags pop off at some point and float to the surface, where they transmit the recorded data to satellites via telemetry, so scientists can download it. If, by chance, the spent satellite tag washes up on a beach and someone finds and returns it, scientists can access even more data.

Satellite tags cost a lot, though (around $5,000 apiece), and are more difficult to deploy, so far fewer of them exist. The lowly dart tag therefore still plays an important role in science and conservation efforts, and various programs exist to enable anglers worldwide to participate.

Tag return rates can be indicative of the relative health of a particular stock of fish. If a particular pelagic species has a high tag-return rate, for instance, that could point to low abundance of that species, theoretically because the tagged fish was one individual among a small stock. Conversely, a low return rate might indicate a healthier stock for the opposite reason.

“Traditional tags provide recapture data, the most valuable in any tagging process,” says Ellen Peel, president of The Billfish Foundation (TBF). “Recapture data provides scientists the ability to advance their understanding of age and growth of fish by comparing initially reported data to data recorded upon recapture. In other words, by knowing how long the fish has been at large, swimming with the first tag, and then comparing estimated weight, a basic awareness is gained on how much the fish grew between tagging events.”

The recapture data and estimates of growth rates get included in stock assessments that calculate the relative abundance of billfish remaining in the water through a sophisticated mathematical model. “The model compares current reported landings with reported landing data over decades to arrive at an upward or downward trend in abundance,” Peel says. “Exact movements are not recorded with traditional tags, but location upon each tagging provides some insight on migration patterns. Locations also provide data on habitat use. Another key component of tagging through recapture data is documentation that caught, tagged and released fish can survive.”

The Billfish Foundation has administered the billfish tagging program since 1990 and has the world’s largest and longest-running private billfish tag-and-release database. TBF also runs a prestigious international tagging competition each year and presents awards for the top tagging anglers and captains from around the world.

The NMFS still runs a Cooperative Shark Tagging Program, as well as a regional Cooperative Billfish Program in the Pacific Ocean. And quite a few research institutions carry out private research tagging initiatives focusing on specific species. But one relatively new tagging program has taken a somewhat different approach.

Gray Fishtag Research (GFR) began as an offshoot of the Gray Taxidermy company and encourages the tagging of all species. “We want people to tag lots of different species and we make it fun,” says Bill Dobbelaer, president of GFR. “We ask people to name their fish, and every tagged fish gets a release certificate.”

The GFR program focuses primarily on charter operations, and tags are free for those crews, although recreational anglers can also participate on their own boats by buying tags. “Charter boats catch a lot of species that they usually let go,” Dobbelaer says, “and putting a tag in those fish adds another element to the trip. Tagging is fun and might make their clients want to go again.”

GFR has tagged some unusual species, including roosterfish in Central America and amberjack off South Florida, and these efforts have provided some surprising statistics. “The conventional wisdom of a one-percent tag return rate doesn’t hold true with those species,” Dobbelaer says. “Our tag return rate on roosterfish is thirty-eight percent, and with amberjack it’s over forty percent.”

This might indicate problems within the stock of fish, but in this case, it’s more likely due to the nature of these particular species. Roosterfish and amberjack live around structure, making them easier to target than true pelagics like marlin, which roam the open sea. But that doesn’t mean they stay in one place all the time.

“We tagged a roosterfish in Costa Rica that was recaptured three hundred and fifty miles away, seventeen days later,” Dobbelaer says. “That’s quite a trip.” Surprising results like this show just how exciting tagging can be. It’s always fun when something you’ve tagged gets caught again, and that’s why Frank Mather’s visionary efforts are still going strong 64 years later.

This article originally appeared in the October 2018 issue of Power & Motoryacht magazine.

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