Where Do Dolphin Migrate?

Guest commentary from Donald L. Hammond, Director of the Dolphinfish Research Program

There was nothing normal about this winter. The southeast had little to no winter. This, coupled with the fantastic October and November dolphin fishing found off Puerto Rico and in the Caribbean Sea in 2011, makes for a complex but interesting set of conditions that will impact the U.S. East Coast dolphin fishing this year. What will 2012 bring?

Dolphin in three regions, the Mid-Atlantic Bight, Gulf of Mexico, and the western north Atlantic tropics (Caribbean and Bahamas), have become increasingly important to completing the puzzle of the relationship of dolphin utilizing U.S. territorial waters. However, tagging in these areas has been very low in the past. Our knowledge about dolphin in these areas has subsequently suffered. In an effort to encourage tagging in these areas, Dolphin Research Program's year-end awards will feature awards for boats fishing specifically in these areas. Sign up for the program, tag dolphin and wine prizes.

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Captain Bouncer Smith of Miami, Florida has done it again, or I should say one of his fish has. The amazing movement of one of his fish is highlighted below lends credence that dolphin from The Bahamas and off the U.S. East Coast likely belong to the same stock.

Which Way Did It Go?

Just as the proverbial question “Who done it?” is associated with paperback mystery novels, “Which way did it go?” is the question associated with long-distance fish movements. The latest tag recovery highlights this question.

This story begins off Miami, Florida, on July 14, 2011, when Capt. Bouncer Smith tagged seven dolphin during a charter trip aboard his boat Bouncer's Dusky. One of these fish, estimated at 19 inches, was recovered 223 days later, February 22, 2012, by Alex Sturges of Charlotte, North Carolina, in the northern end of Exuma Sound, Bahamas, during a fishing trip on the Patsea VII. The fish was estimated to be 42 inches in fork length and weighed approximately 20 pounds. This fish grew an estimated 23 inches in the 32-week liberty, which would mean that it averaged growing 0.7 inches per week.

With a liberty period spanning more than 7 months, the fish could have traveled 4,800 miles if it only maintained the average of 21.8 miles per day observed for other Florida dolphin traveling up the East Coast. This piece of information opens up many possible routes.

One of the shortest routes would take it from Miami into the Providence Channel through the Bahamas Bank into the Atlantic where it could turn south traveling toward the south end of Cat Island to enter the southern reaches of Exuma Sound. This route covers 550 miles requiring the fish to maintain a leisurely pace of 2.47 miles per day to complete the trip.

An alternate and much longer route would take the fish up the Eastern Seaboard to the area off Montauk, New York. There it might turn southeasterly, moving out into the Atlantic where it could utilize intermittent southerly counter currents to travel down to the southern end of Cat Island, Bahamas, to enter the southern end of Exuma Sound. This route would take it 2,700 miles which would require an average daily travel of 12.11 miles per day.

Even if we speculate that the fish traveled from New York down to Anguilla Island on the northeast corner of the Caribbean Sea before turning west to Cat Island, it would only add 1,200 miles to the distance. This would require the fish to speed up to an average of 17.5 miles per day. The faster pace is still 20 percent less than the average speed of dolphin traveling up the U.S. East Coast.

Moving beyond the route the fish took, the point is that a dolphin from Florida's east coast traveled to the north end of the Exuma Sound, Bahamas. This completes the relationship of the dolphin found in Exuma Sound with those off Florida. The first half of the story came from a dolphin tagged by Mark Mitchell in April 2009 in the north end of Exuma Sound that was recaptured 44 days later by James Childs off Ft. Pierce, Florida, a distance of 620 miles. Capt. Bouncer's fish shows there is a two-way exchange between dolphin in these two areas.

Numerous fish tagged on the eastern side of the Bahamas have been recovered along the U.S. East Coast from Ft. Pierce up to New York, showing the movement of fish to the west. In April 2010, a dolphin tagged off Marathon, Florida, in June 2009 by Don Gates was recovered by the boat Reel Excuse off Long Island, Bahamas, at the southern end of Exuma Sound. This suggests that dolphin found along the east side of the Bahamas and off east Florida will readily move between the two areas and possibly the entire U.S. Eastern Seaboard.

The bottom line is that fish found off the Bahamas and off the U.S. East Coast likely belong to the same stock. FS

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