Outdoors column: Dolphin tracking opening new doors

For about the last 17 years, Don Hammond has been focused on studying the habits, growth rates and, most importantly, the migratory patterns of dolphin in the North Atlantic Ocean, the portion of the great Atlantic north of the equator.

Hammond is a retired marine fisheries biologist from the S.C. Department of Natural Resources who established the Dolphinfish Research Program in 2002 through his research organization, Cooperative Science Services, LLC. Plus, the prior four years leading up to his retirement, Hammond was heavily involved with a S.C. DNR study of the colorful, prolific pelagics.

Hammond, a Charleston resident, and his cohorts have tagged over 19,000 dolphin over the course of the program. But thanks to a $26,000 grant from the Guy Harvey Ocean Foundation, Hammond has been able to take his tagging program, and the data gleaned from it, to a new level.

The donation provided the funding for a pair of satellite tags to be deployed on dolphin, with these tags programmed to monitor the fish's movements for six months instead of the 30 days previous tags used in the program were for programmed for.

On June 3, 2014, Hammond was able to implant the tags in a pair of bull dolphin on a trip off Charleston aboard My Three Sons, owned by Hunter Edwards. Thus began the odyssey of Dolphin GHOF-01.

While Hammond was hopeful one of the tags could stay with a dolphin for the entire half-year, he wasn't tremendously optimistic. Only three of the 18 previous 30-day tags Hammond deployed provided data for the full 30 days.

When the other dolphin fitted with a tag was eaten by a predator only 36 hours after being fitted with it, Hammond was even less optimistic.

But, on Dec. 2, 2014, almost exactly six months later, Dolphin GHOF-01's archival tag released itself from the fish and soon made first contact with a satellite about 44 miles northeast of Punta Cana, Dominican Republic.

Hammond said the tag spent the next 23 days downloading data via the ARGOS satellite system as it drifted through the Mona Passage between Puerto Rico and the Dominican Republic, heading southwest into the open Caribbean Sea.

The information provided on the fish's movements during the six-month stretch were amazing to Hammond.

After being released offshore of Charleston, the dolphin traveled in a general northeast direction, north of Bermuda, then east and then a south-southwest direction before the tag released itself from the fish near the Dominican Republic.

In all, the fish traveled over 8,000 miles in the six months, and that is, as Hammond said, smoothing out the fish's movements.

“It just boggles my mind,” said Hammond earlier this week. “When we started processing the data and saw this fish has traveled 8,100 miles I said ‘What?’ How many tail wags is that? That's straight-line movement, and they move laterally. Nature is amazing – what God has put together is mindboggling. We’re just beginning to scratch the surface of dolphin.’”

Hammond combines the confirmed migratory track of Dolphin GHOF-01 with a dolphin tagged in 2012 to complete the general circle of migration he believes dolphin make in the North Atlantic.

The tagged fish recovery from 2012 confirmed that dolphin moved from near San Juan, Puerto Rico to off Georgetown. That fish’s projected route, through the Old Bahamas Channel to the Florida Straits and then up the East Coast, covered an estimated route of 1,600 miles.

“(Combining the two routes) shows the closed circle of the migration routes of these fish,” said Hammond. “That's one thing this study initially proved was there are three supply lines for dolphin (along the East Coast). First is from the Gulf (of Mexico), from the loop current in the gulf to the Gulf Stream. The second is the Old Bahamas Channel which runs along the north of the Caribbean Sea towards the Keys and comes out near Key Largo and up the Gulf Stream.

“Third is along the east side of the Bahamas and catches the Gulf Stream near Fort Pierce (Fla.) This route is far more important for the Carolinas fishery. I think that's where the majority of our fish come from.”

Hammond, though, is hesitant to be absolutely sure of the migratory pattern of dolphin, but he has his opinion.

“The first satellite tag recovery could be written off as an anomaly,” said Hammond. “If we get get a second recovery that is similar, it may suggest a pattern may be developing. Get a third one, then ‘OK, this is a pattern.’ We have to replicate it.

“Personally, yes, I absolutely think we’re going to prove this is the normal pattern for our dolphinfish.”

Local Dolphin

Local boats have caught a few dolphin on offshore trips this week, but the big appearance of the migratory fish anglers are eager for is yet to come. It won't be long, Hammond says.

“I predict the third week of April, it’s going to break loose,” Hammond said. “They're already catching a few now (off South Carolina). One boat out of Edisto caught six and they were targeting wahoo.

“They're catching them in the Keys and in the Bahamas.''

Considering Dolphin GHOF-01 traveled as far as 150 miles in a single day during the six months with the satellite tag implanted, you can bet the dolphin will be here en masse before you know it.

This story was originally published April 9, 2015 at 6:17 PM with the headline "Outdoors column: Dolphin tracking opening new doors."