Tarpon are one of the most iconic saltwater fish in the Southeastern and Gulf states. Many anglers spend their life dreaming of hooking a tarpon that could easily exceed 100 pounds, which are known to fight fiercely, often leaping entirely clear of the water in their efforts to shake a hook.
The tarpon fishery, which extends from Texas to the Carolinas in the U.S., is, by some estimates, a multi-million-dollar-per-year industry, and the fish is tied deeply to local culture.
Yet, despite the legendary toughness of the species, the tarpon is listed as "vulnerable" by the International Union for the Conservation of Nature (IUCN), and their populations seem to have been affected by fishing, degraded water quality and habitat loss.
Recently, guides have been increasingly reporting that sharks are taking a bigger bite out of the tarpon catch in recent years, and may in fact pose a risk to the species' survival.
But, until now, there's been no hard data on just what the depredation rate might be, which makes it difficult to make informed conservation decisions, for either the tarpon or the hammerheads.
The Rising Predation Rate
Jakob Owens/Unsplash
In wave-making research recently published in Marine and Coastal Fisheries, a team of researchers, led by biologists at the University of Massachusetts Amherst, has quantified the rate at which great hammerhead sharks are eating Atlantic tarpon hooked by anglers at Bahia Honda, Florida-one of the prime tarpon fishing spots in the Florida Keys.
Called the "depredation rate," the team found that 15.3% of tarpon that were hooked by anglers and fought for more than five minutes were eaten while still on the line.
The team discovered this alarming trend at Bahia Honda, a renowned tarpon fishing spot and a putative tarpon prespawning aggregation site.
Using visual surveys of fishing in Bahia Honda, they quantified depredation rates and drivers of depredation. With acoustic telemetry, they simultaneously tracked 51 tarpon and 14 great hammerheads, the most common shark to depredate tarpon, to quantify residency and spatial overlap in Bahia Honda.
The researchers found that depredation risk was highest in the first 5-12 minutes of the fight and on the outgoing current.
They also observed that during the spawning season, great hammerheads shifted their space use in Bahia Honda to overlap with tarpon core use areas.
Great hammerheads restricted their space use on the outgoing current when compared to the incoming current, which could drive increased shark-angler interactions.
While alarming at first glance, experts argue that this heightened predation rate is not necessarily a sign of an ecosystem out of balance.
Increased reports of depredation are to be expected, especially as great hammerhead sharks, listed as critically endangered by the IUCN, are seeing their population stabilize in the southeastern United States; the result of decades of conservation and management efforts.
At the same time, angling is an increasingly popular sport, which means that there is a greater chance for human-fish-shark encounters.
The researchers' findings have ignited discussions among conservationists and anglers alike on potential modifications to fishing practices to safeguard both the tarpon and shark populations. These dialogues underscore the intricate dance between human activity and marine life sustainability.
Some of the suggested solutions include reducing fight times, using circle hooks, cutting the line when a shark is near, and avoiding fishing during peak shark activity periods.
These measures could help reduce the stress and mortality of both tarpon and sharks, and ensure the long-term health of these charismatic species.
The researchers hope that their study will raise awareness of the complex interactions between sharks and tarpon, and inspire further research and collaboration to protect these valuable marine resources.
