Friday, August 11, 2006

Dolphin tagging program provides a lot of interesting information

Don Hammond is past the midpoint of year five in the Dolphin Tagging Research Project, a scientific study which involves tagging of the prolific pelagic species by recreational fishermen along the Southeast Coast and their subsequent recapture.

A total of 38 tags were returned this year as of Tuesday, giving Hammond plenty of information to analyze about the travels and growth patterns of the colorful, feisty and popular gamefish.

Twenty-seven of those fish had been recaptured by the end of June, marking the second highest number of recaptures for the first half of a year in the project's history.

As usual, the data from the returned tags reveals amazing and varied migratory patterns by dolphin.

The father-son team of Don and Justin Brown of Pembroke Pines, Fla., aboard Draggin' Dreams have tagged a large number of dolphins for the study, many while fishing off Islamorada in the upper Florida Keys.

The duo has tagged more than 700 dolphin since the study was originated in 2002 by Hammond and the South Carolina Department of Natural Resources.

Several dolphins tagged by the Browns revealed amazing details of the movement of the species.
One fish tagged by the Browns off Islamorada on May 26 was captured on July 16 near Block Canyon off Montauk, N.Y., 51 days later and 1,200 miles away. The fish traveled an average of 23.5 miles per day.

"That is a new domestic travel record for a [total] distance moved by a single fish," said Hammond. "That fish virtually moved the entire length of the Eastern Seabord that is utilized by dolphin."
Other fish tagged by the Browns exemplified just how swiftly dolphin can travel over a shorter period of time.

Another specimen was tagged by the Browns off Islamorada and, in Hammond's words, "was at liberty," for 15 days before it was caught off Cape Lookout, N.C. That fish traveled 702 miles during the span, an average of 46.2 miles per day.

"They very easily can travel even 50 to 100 miles per day," said Hammond, a retired biologist from S.C. DNR who now operates the dolphin project through Cooperative Science Services, LLC, out of Charleston.

Other tagged dolphins that have been recaptured this year have shown individual fish don't always travel as far. One characteristic they all have in common, though, is they are very fast growers.
Hammond cites a dolphin that was tagged offshore of Marathon in the middle Florida Keys and was captured 58 days later off Miami, approximately 100 miles away.

That fish measured 18 inches and weighed about 3 pounds when tagged and had grown to 32 inches and nearly 10 pounds when caught off Miami.

"That in itself shows there is real good justification for releasing small dolphin," Hammond said. "Give it two months and now you've got an 8-10 pound fish. An 18-inch fish has barely enough meat on it to make a sandwich. It's worth it isn't it [to release the small fish]?"

Hammond has gathered some other interesting tidbits from the study:

Hammond continues to scratch his head over the fact that no dolphin tagged in Florida has been recovered by an angler fishing in South Carolina waters in the history of the project.

Hammond points to a couple of possible causes.

"There is a natural push of the sargassum to the eastern side of the Gulf Stream and the dolphin may move to the eastern side of the Gulf Stream," Hammond said. "South Florida is like the gauntlet and it may push them to the eastern side ... to try to get away from the fishing pressure. The fish could very likely be passing by our coast beyond the reach of the anglers [on the eastern side of the Gulf Stream]."

Hammond noted large dolphin have been commonplace, especially in South Florida from Stuart to the Keys.

"It's been a phenomenal year for big dolphin," said Hammond. "This year we've seen probably more 50-pound dolphin caught off the Eastern Seaboard than in the last 20 years.

"Everybody down there [in South Florida] is talking about it."

The largest Hammond's heard of? An 84.6-pounder caught June 17 off Nassau, Bahamas.

Quick "Facts about Dolphins"