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October 06, 2003

Live Fast, Die Young

The remarkable life of the perfect pelagic - the dolphin.

The Islamorada captain called down from the bridge: "Dolphin!Dolphin! Get the lines out! Tie some jigs on ... just get 'em inthe water!" Thousands of neon fish flashed beneath the boat,brilliant in relief against a rich cobalt sea. We hooked upinstantly, two by two, sometimes triples. Taut lines twanged as aboatload of people danced delicately around each other, and matesthumped fresh mahi on the deck.

In 1970 (as in so many years), Florida Keys dolphin ran thick asthieves. Boats returned to port on most summer days with fish boxesbrimming, captains confident of an extra tip plus the bounty fromselling their catch. I was 12; I had never seen so many fish. Andwhile I loved my home waters inside Tampa Bay, I became a confirmedblue-water angler that day.

What the average dolphin lacks in size compared with otherpelagic brawlers such as billfish, tuna and wahoo, it makes up forin attitude and abundance. Even small peanut dolphin can be greatfun on light-spin or fly rods. Bull dolphin weighing up to 80pounds (88 pounds is the current all-tackle record) will wear outarms and stout fiberglass as they plane away from the boat,creating tremendous broadside pressure with their massive,prominent heads.

During a long day of trolling, dolphin truly spice up the act.In fact, some references say the dolphinfish, mahimahi, dorado(Coryphaena hippurus) may be the most popular saltwater game fishin the world, if not the perfect game fish. "Mahi" in Hawaiiantranslates as strong and athletic, similar to the English "macho"when describing a man, according to Fishing Hawaii Offshore by JimRizzuto (www.KonaFishing Chronicles.com). Doubling the word -"mahimahi" - doubles the intensity of the meaning. Also, "dorado"in Spanish means gilded or golden.

Among the oldest recorded images of dolphin is a fresco dated1500 B.C. at the National Archaeological Museum of Athens. Thepainting depicts a man and his catch of fish, and the fish areunmistakably dolphin. Little lore or mythology seems to exist aboutdolphin, although the constellation Dorado, introduced byastronomer Johann Bayer in 1603, obviously illustrates commonknowledge of the fish. Dorado, a southern constellation, containspart of the Large Magellanic Cloud, an irregular galaxy that orbitsthe Milky Way. Some older star atlases call the constellationXiphias, the swordfish, though an outline of the stars shows noprotruding bill.

Dolphin stand out physically because of their striking blue,green and gold colors. Males, or bulls, feature blunt, prominentforeheads that may allow other fish to recognize gender differencesor may indicate the animal's fitness to a potential mate. Commondolphin have few relatives, linked only to the pompano dolphin(Coryphaenas equiselis), which grow up to 4 feet long and travel inwaters farther offshore. Pompano dolphin can be mistaken forjuvenile or cow dolphin and have been found in the same schools ascommon dolphin. Pompano dolphin can be distinguished by theirgreater body depth and by the absence of longer rays at the startof the anal fin.

Omnipresent and Voracious
Dolphin swim in most of the world's tropical and subtropicaloceans, which automatically makes them a good candidate for "mostpopular." Dolphin also feed voraciously and throw an aerial displaybarely bested by an Olympic gymnast. But what truly makes thedolphinfish unique - perfect, if you will - is its incrediblebiology and habits.

Dolphin grow rapidly, migrate great distances and eat literallyeverything that swims. That heavyweight, 88-pound world-recorddolphin - caught in 1998 in the Bahamas - had lived less than fiveyears. The age of four is elderly for dolphin. That makes the"playboy" adage "live fast and die young" quite apropos for thesefish.

"If dolphin are not the fastest-growing fish, they're close,"says Don Hammond, marine fisheries biologist with the MarineResources Division of the South Carolina Department of NaturalResources. "Work is being done on wahoo and marlin, and they havesimilar growth rates."

Juvenile dolphin have been reported to grow 1.3 to 2.7 inches inlength per week, Hammond's background research shows. In fact,dolphin can reach 4 feet long and weigh 40 pounds in less than ayear!

But that's not all. Dolphin can reach sexual maturity in threemonths and at no more than 14 inches long; all dolphinfish reachmaturity by the time they're 22 inches long. Compare that with afish like red drum, which usually reach maturity at age four andabout 30 inches long.

Once they begin to spawn, dolphin apparently continue spawningalmost continuously. They have to. "Most dolphin live less than 18months," Hammond says. "Their annual mortality rate is estimated tobe 99.7 percent, which means only 0.3 percent make it past 12months of age."

Dolphin die early because of their own biology, but also becauseeverything eats them, including larger dolphin. Dolphin could becalled the menhaden of the open ocean.

Because they live on the edge, so to speak, dolphin themselvesmust consume mass quantities of food to fuel their rapid growth.Dolphin in captivity have been known to eat 20 percent of their ownbody weight in food a day. That's like watching a 6-foot man whoweighs 200 pounds eat 40 pounds of food - say, 160 hamburgers or 30steaks.

More on the Menu
When scientists inspect the stomachs of dolphin, they never knowwhat they might find. Small jacks, flying fish, sea horses,triggerfish, squid and crabs are common prey. In the Atlantic Oceanoff the United States, these species can all be found near thefloating sargassum-weed communities notorious for holding schoolsof dolphin. Summer's southeast trade winds push weed lines from theSargasso Sea in the middle of the ocean toward the East Coast.Dolphin also orient to flotsam such as lumber, plastic bags andother trash and debris, which hold juvenile fish.

Preferring warm water - 70 to 90 degrees - dolphin cruise theopen ocean and coastal seas in search of food, high salinity andhigh oxygen content, all of which help support their metabolicrates, Hammond says. Younger dolphin school more readily than olderfish, especially bulls, which tend to break off into smaller groupsor become solitary once they weigh about 25 to 30 pounds.

With the dolphin's widespread popularity, it was only a matterof time before questions of abundance arose, at least for southeastU.S. anglers who commonly target dolphin in tournaments."Commercial fishing for dolphin started to increase in the early1990s, but it didn't reach a significant level until 1995," saysHammond. "Commercial fishermen then began to directly targetdolphin. Boats in South Carolina were offloading 10,000 to 20,000pounds per trip. Anglers suddenly had to troll around longlines insome of their favorite fishing areas. That got the attention offishermen."

Anglers, scientists and fisheries managers became concernedabout the increasing pressure on this fully utilized species.Federal councils governing the South Atlantic, the Caribbean andthe Gulf of Mexico tried to reach a consensus about dolphin andwahoo, but the joint plan suffered delays, and the Caribbean andGulf portions failed to include proper bycatch measures.

In 2002, the South Atlantic Fishery Management Council, whichformulates and proposes regulations for fisheries and essentialhabitat in federal waters from North Carolina through southeastFlorida, asked to proceed alone with its portion of the project.With permission granted, the council approved a Dolphin/WahooFishery Management Plan this January and sent it to the secretaryof commerce for review. The plan would set commercial andrecreational limits, including a 10-fish bag limit per day perangler. At press time, the plan was still pending, awaiting thesecretary's approval of a sargassum management plan, which wasexpected in mid-July.

At the same time, Hammond reviewed the council's data on dolphinand saw that little information existed about the fish's movementsand migration. Scientists theorize that the stock of dolphin foundoff the U.S. East Coast includes fish from the Bahamas and thenorthern Caribbean, possibly even Bermuda. This Atlantic stock maymix with Gulf of Mexico and western Caribbean dolphin, but morescientific data must be collected to confirm the theories and toprove genetic differences or similarities between the stocks.Hammond launched a three-year dolphin-tagging project in 2002 inSouth Carolina, but that effort quickly grew to include all of theSoutheast as anglers eagerly signed on to tag-and-release fish.

Far-Flung Fish
Tagging began in April. By the end of 2002, 350 anglers had signedup for the program, and 463 fish had been tagged: 379 by anglersand 84 by South Carolina biologists.

Of the fish tagged, 10 were recaptured. Those fish averaged 42days at liberty and traveled an average of 260 miles, or 6.7 milesper day. Previous studies have shown dolphin capable of swimming 80miles in a 24-hour period, Hammond says. Those studies, conductedin the early 1990s by Mote Marine Laboratory in Sarasota, Florida,involved too small a sample of dolphin (67 fish tagged; fourrecoveries) to reach the broad conclusions Hammond wants tomake.

The initial recoveries of fish tagged in 2002 occurred offFlorida, as Hammond suspected. The first fish caught demonstratedto scientists that capture and tagging had little effect on thefish's feeding behavior. It was recaptured the same day it wastagged off Sebastian. Among the remaining nine recaptures, one fishtagged off Cape Canaveral traveled 186 miles north to JekyllIsland, Georgia. Fish tagged off South Carolina went to Big Rock,North Carolina, and other points north and east. One made it allthe way up to Providence, Rhode Island (644 miles in five months).It was recovered in late October, at a time Hammond expected mostdolphin to have headed south.

"That kind of opened the door. It appears that fish remain inthe Mid-Atlantic Bight for a longer period of time than previouslythought," he says. This year, the number of angling participantsincreased to more than 500; by late June, 600 dolphin had beentagged. Hammond has also logged 14 more returns - six were taggedand recovered off Florida. Two fish tagged from the same school offKey West on March 1 were recovered two to four weeks later off FortPierce and Jupiter.

"This is something that has been shown from genetic studies -that fish taken out of the same school have a closer genetic link,which implies school fidelity among spawned fish," he says. "Inother words, fish from common parents will stay together."

This school apparently swam from the Keys to the central eastcoast of Florida, but remained there for a few weeks. Hammond saysthat raises further questions about migration patterns: Did thefish stop to feed on a large pod of bait? Was there some cold-waterbarrier to the north? Another Florida fish, tagged off Miami inearly May, was recaptured at the end of the month off Hatteras,North Carolina.

While the study, to date, has revealed a definitive - andexpected - south-to-north migration along the East Coast duringspring, many questions remain unanswered. Earlier studiesdocumented two recoveries of dolphin tagged off Cozumel. One fishwas caught off Pensacola, the other off Fort Lauderdale, linkingthe western Caribbean fish with those in the Gulf and even in theSouth Atlantic. But more study is needed.

And what of the fish that linger throughout south Florida duringthe summer? Where do they come from? Hammond asks. After July 1,dolphin tagged off south Florida have shown no indications ofnorthward movement, he says. Perhaps fish from the westernCaribbean arrive to replace the dolphin that move north inspring?

Add to that the anecdotal information from fishermen who saythat dolphin caught off the eastern side of the Bahamas from Marchto June dwarf the smaller fish caught off south Florida. Could thestock separate as it moves north, with larger fish transitingfarther offshore along the eastern edge of the Gulf Stream and onto Georgia and the Carolinas?

"This study has provided good information, and it's raising morequestions about the fishery and the stocks than we thought aboutpreviously," Hammond says. "Our dolphinfish are involved inmultinational fisheries along several nations' coasts. It's goingto take international treaties to manage them." CaptiveAudience

The dolphin's rapid growth capability has fueled interest infarming the species at commercial aquaculture facilities. In Hawaiiand Australia several companies have investigated methods ofgrowing dolphin in pens offshore and in man-made facilities andgrow-out ponds flushed with fresh seawater piped inland from thecoast.

Steve Nel of Marine Farms in western Australia hopes to beginproduction at his farm near Exmouth on the coast this fall, withshipments of fish by June 2004. Nel operates a research anddevelopment facility near Perth, where he says he's successfullygrown dolphinfish to market size.

"Within 10 years or so, Marine Farms believes more mahimahi willbe produced around the world than salmon is today," Nel states onhis Web site: www.marinefarms.com.au. "This is possible due to thespawning capability, rapid growth and food conversion efficiency ofthe fish."

Mature mahi spawn every second day, Nel says. Under intensiveaquaculture conditions, the fish will grow from an egg to marketsize (about 10 pounds) within eight months. While dolphin may beraised in offshore pens, and another Australian company hasrequested permission to begin such a practice, Nel says land-basedsystems can be more easily controlled. He can also properly treatwaste water to maintain an ecologically sound facility.

That said, he does see other areas where sea cages may be moresuitable, such as where sheltered water may be available andcoastal land is too expensive. Nel expects his farm to produce550,000 pounds of dolphin per year initially, increasing to 4.4million pounds within five years. Supply is expected to remainconstant throughout the year, and fresh chilled whole fish will beavailable at any size from 5 to 10 pounds. Now that's a largeschool of mahi!

Want to Tag
Among the 500 anglers signed up to tag fish for the South CarolinaDolphin Tagging Project, more than 300 live in Florida or SouthCarolina. Project coordinator Don Hammond hopes more anglers frommid-Atlantic states will participate to better track the coastaldolphin migration.

Anglers can sign up online at www.dolphintagging.homestead.comand receive a tagging kit, complete with standard external streamertags. These tags sport a nylon dart head and a polyethylenestreamer imprinted with information about what to do when that fishis recaptured.

"I ask that anglers who catch a tagged fish keep the fish," saysHammond. "The data it can provide is too valuable to chance comingup with the wrong numbers. I ask them to measure the fish, givingus the fork length, and weigh the fish, then send in theinformation with the tag."

So far, 255 different anglers have tagged fish aboard 117 boats.With 24 recaptures, Hammond estimates he's seeing a 2-percentrecovery rate. "When dealing with such a highly pelagic species, a1-percent recovery rate is generally accepted. I'm very pleased sofar. As we get more larger fish tagged, I hope the recovery ratewill increase," he says. Anglers who tag five or more dolphin,captains whose passengers tag 10 or more, and anyone who recovers atagged dolphin all earn a project T-shirt.

Initially, project funding came from two South Carolina sources:the South Carolina Governor's Cup Billfishing Series and thesaltwater license fund. As the project expanded, Hammond soliciteddonations from private businesses and sport-fishing organizations.For more information, visit www.dolphintagging.homestead.com.