The Importance of Researching Dolphinfish

Data is being collected on the ecological and economic importance of dolphinfish. Keith Alexander Lee

Sitting on his patio swing on Cudjoe Key, surrounded by hanging orchids and drooping palm fronds, Don Gates shares a memorable story from the Dolphinfish Research Program (DRP). A fishmonger at a Whole Foods in Omaha, Nebraska, was inspecting a 30-inch dolphin fillet when they noticed something in the flesh: a spaghetti tag. The fish was sourced from North Carolina. It was ­likely caught in the South Atlantic Bight during commercial longline operations.

From the South Atlantic to the Cornhusker State to the grill of a local resident, such is the troubled existence of Coryphaena hippurus.

“The dolphin is an oceanic species that we thought could never be overfished,” says marine artist, marine biologist and conservationist Guy Harvey, whose namesake foundation is the largest sponsor of the DRP. (One of his mahi paintings is the DRP logo.) “Well, here we are, and dolphin are overfished, not only by recreational anglers, but because of the nationwide demand for the mahi fillet or mahi sandwich. There is a cost to the dolphin population in the western Atlantic and eastern tropical Pacific. These fish are not farm-raised.”

While in its 24th year of ­operation, the DRP feels uniquely created for this moment. Its goal, both now and upon its founding, is to collect vital information on the ecological and economic importance of dolphinfish, including documenting growth rates, migration routes and natural behaviors, to inspire more research and allow scientists and managers to better understand local and regional fisheries. The best part: Anglers are driving the research. 

As of press time, this citizen-­powered tagging program had deployed 37,708 dolphinfish tags. DRP executive director Wess Merten says, “We estimate that 1,642 individual vessels have participated in our program, with as many as 4,924 anglers in 25 countries tagging fish.” 

Gates is the LeBron James of this initiative. Now in his 23rd year with the DRP, Gates’ team reached 5,000 tagged dolphin in June 2024. Since 2017, Gates has averaged 364 tags deployed per year. His Facebook page is populated with photos and videos of him and his crew aboard Killin’ Time II, a 25-foot Parker with a Guy Harvey dolphin wrap. In the pictures, Gates smiles broadly as they release tagged fish after tagged fish. 

“By maintaining a high level of tagging participation, we can generate more recoveries, which adds to the ability for the DRP to meet several key research objectives, such as better describing the species growth and movement dynamics along the US East Coast and ­international locations,” Gates says.   

Those 37,000-plus tags and resulting data have led to some memorable findings. “Through our tagging participation, we know mahi move throughout the western Atlantic, Caribbean and Gulf,” Gates explains. “Our tagging records have also ­documented that the species is capable of growing on average 0.45 inches per week.” 

Data collected with the public’s help has been published in 15 scientific publications that describe the species’ movements, genetic structure, vertical habitat use, oceanographic preferences, status among international fisheries and more.         

“Not only is there a great need for more data on the ­seasonal movements of this species, but Wess has created one of the biggest citizen-science tagging projects along the Southeast coasts of the US and in the Caribbean,” Harvey says.

But back to the demand for the fish sandwich. The current volume of undersize mahi being harvested, both commercially and recreationally, is not sustainable. “Too many fish are being retained that are juveniles, either less than 20-inch fork length or those fish that are just starting to mature. Any trip to a marina or a social media post will confirm this,” Gates says. “These fish need to breed before they are harvested. A 20-inch fish on average is four to five months old and is just starting to breed.”

To reduce overfishing of this key species, the Guy Harvey Foundation proposes much higher minimum sizes (30-inch fork length) and a closed season, with no possession permitted from April to July in the western Atlantic, Caribbean and Gulf. “This species reproduces rapidly, and a four-month moratorium will allow the species to build back its population,” Harvey explains.

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The DRP is always looking for more people to power its research. “Anglers can help support or participate in our program by tagging fish or financially contributing to our nonprofit, Beyond Our Shores,” Merten says.

To incentivize participation, the DRP rewards top taggers with a chance to fish at the legendary Tropic Star Lodge in Panama. Gates was a well-­deserved recipient of this trip in December 2023. Merten and Harvey attended as well. They tagged 70 dolphin in three and a half days.

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