Sport­fish­ing

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

Power & Motor Yacht - - IN THIS ISSUE - By John Brown­lee

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

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

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