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Dolphinfish Research Program achieves substantial milestones

by Grady-White 2 Aug 2023 16:13 UTC
Dolphinfish research program achieves substantial milestones © Grady-White

The Dolphinfish Research Program, now the largest initiative to investigate the movement and population of dolphinfish, was started by Don Hammond in 2002 with a grant from the South Carolina Department of Natural Resources (SCDNR).

When the state's funding ended in 2005, Don retired from SCDNR to work on the program full-time. Beginning in 2006, the first year as a private initiative, Grady-White Boats, along with a number of angler's clubs along the east coast, were the primary supporters of this important program. Today, with the aid of many additional supporters and anglers who tag the fish, they've learned a great deal about the migration of dolphinfish in the Western Central Atlantic Ocean. Recently, we spoke with program director Wess Merten to learn more about some of the fascinating information they have uncovered over the past 20 years.

With tagging numbers expected to hit over 34,000 in 2023, the program has seen many significant milestones. One success that has never been achieved by any tagging program before or since, occurred between June 2014 and December 2014. A satellite tag deployed by Don off Charleston, South Carolina, on a 43" bull was tracked for a six-month period before the tag detached from the fish off Punta Cana, Dominican Republic.

Wess describes this success as incredible. He says "This is a feat that hasn't been replicated after a decade of deploying satellite tags. The record continues to amaze us because neither our program nor other researchers around the world have been able to replicate it." He continued, "Longer movement is more information gathered. Seeing exactly where this fish was for six months led to a super valuable data set that was reliable, because it was uninterrupted. Not only did we get to observe where this fish was during certain months, but the data supports a central theory that these fish move in an annual circuit around the Western Atlantic Ocean."

The extended tagging period provided the program with an unprecedented opportunity to gather comprehensive and invaluable data on the behavior, migration patterns, and habitat preferences of the bull. Another milestone is the sheer number of fish tagged and the wealth of knowledge that has been obtained by the information gathered from more than 800 recaptures. The program relies on commercial and private fishermen around the world to tag, recapture, and report dolphinfish data continuously in order to provide a consistent status update on the stocks. By placing and recapturing so many conventional tags, the program has been able to document how mahi are moving, and how they can be better conserved. The most important information obtained from the success of the program is the ability to describe the species migration pattern in the Western Central Atlantic Ocean. The six-month satellite tag, their 53 other satellite tag deployments in the Atlantic, and conventional tagging database support a circuit-like migration pattern. Along this migration pattern, data supports that dolphinfish can move up the entire East Coast in just 35 days, move slower through the Tropical Atlantic than the Caribbean Sea, and can move from the U.S. Caribbean Sea to the U.S. East Coast in 2-4 months.

With angler participation and their database growing, some may ask why it is so important to research and conserve a species of fish that is so massive in population. Primarily, dolphinfish sit directly in the middle of the food chain - feeding on smaller fish and acting as prey for larger sharks and billfish. Therefore, the movement of this species directly impacts the movement of other species. First, by studying dolphinfish, we are able to study pelagic food webs and see where other species that rely on them move as well.

Second, dolphinfish do not reach sexual maturity for at least 4-5 months. By promoting the release of immature and undersized dolphinfish, this supports a healthier future spawning biomass and stronger future recruitment for the stock. Third, collecting data on the size of the fish tagged and recaptured allows the program to calculate growth rates and examine how these may vary by sex, region, and time of year. Lastly, the program has shown dolphinfish have an impressive migratory behavior, covering vast distances during their lifetime. This exposes them to various environmental factors, including climate change, pollution, habitat degradation, and overfishing. Understanding their migration routes, life history patterns, and population dynamics allows the Dolphinfish Research Program to suggest conservation and management measures to the appropriate government agencies to safeguard the stock, thereby preserving the population and ensuring sustainable dolphinfish management.

From these successes, the program continues to grow and they are now replicating their tagging effort on dolphinfish with wahoo. Wahoo is another species that has not garnered as much attention in the past yet is extremely important to recreational and commercial fishing interests. With more boats fishing every year, there is a lot of debate about not only the dolphinfish population, but also wahoo. Another pilot program is taking place in Puerto Rico where the Dolphinfish Research Program has partnered with area restaurants to track how much dolphinfish is being purchased and consumed. This tracking has recently revealed a steep decline in dolphinfish available for purchase from local fishermen, leading the program to recognize the need to research what is causing the decline in dolphinfish populations in that region. This is also happening in the Florida Keys, where anglers are reporting that they are seeing less fish, and that the fish they do see are smaller than previous years.

To keep up to date with the Dolphinfish Research Program you can sign up to receive their monthly electronic newsletter here.

To become part of the Dolphinfish Research Program:

NOTE: If you have participated in the Dolphinfish Research Program by tagging or having caught a tagged dolphinfish on your Grady-White boat, please email us! We'd like to feature you in an upcoming story.

If you want to be part of protecting the dolphinfish population, consider only shopping for seafood or consuming seafood in restaurants that offer environmentally sustainable choices. The Monterey Bay Aquarium's Seafood Watch website outlines seafoods into three categories: Best Choices, Good Alternatives, and Avoid. Make a point of reviewing this information or go online and find a pocket guide to keep with you when making your seafood selection.

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