FGCU professor's research could lead to a brighter future for endangered sea turtles
A Florida Gulf Coast University professor’s work is illuminating a way to help the world’s threatened sea turtles.
Nets used by fishermen or shrimpers can be deadly to these ancient mariners, as FGCU professor Phil Allman calls them, when the turtles get entangled and drown, but his new paper details a simple, low-cost way to keep them safe: LED lights.
Allman, a vertebrate zoology associate professor and a 2006 Fulbright Scholar, found that installing a series of green lights on the edges of the nets reduces the number of endangered sea turtles killed as "bycatch", the untargeted creatures unintentionally ensnared in mesh traps intended for other species.
Allman has just published his research in the scientific journal “Conservation Biology” after years of study with West African fishermen along Ghana’s coast. Researchers followed 15 fishing boats six days a week for a full year, “These observers went out with a boat on every single fishing trip for a full 12-month period," he said. The carnage they documented was sobering. "Those 15 vessels in that single year captured 64 turtles," he said. "That equates to about 4.3 turtles per boat per year.”
Doing the math with the country’s fleet of 12,000 boats, “That would represent 48,000 turtles just in Ghana being captured in a one-year period.”
Allman’s work on a way to keep the endangered creatures safer comes at an opportune time for the popular reptiles. A coalition of U.S. conservation groups intends to sue the National Marine Fisheries Service for what they call a drastic weakening of rules to protect them.
Sea turtles are citizens of the world, traveling thousands of miles and over national boundaries from their nesting beaches. All five sea turtles found in U.S. waters are protected by the Endangered Species Act and would be harmed by this rule, which becomes effective in April, says Jaclyn Lopez, the center’s Florida director.
The shrimp industry also poses hazards for sea turtles. Florida has long required shrimper trawlers to include what are called turtle excluder devices, which are an escape hatch that let them swim to safety.
However, a late move by the Trump administration reversed course on a proposed rule about turtle excluder devices in shrimp trawl fisheries in the Gulf of Mexico and South Atlantic, said Lopez, reducing the measure’s effectiveness by more than 50%.
According to the nonprofit, conservative estimates suggest that, on average, shrimp trawlers routinely kill and discard about three pounds of unintended “bycatch” for every pound of shrimp they haul in. The bycatch includes thousands of sea turtles that drown every year along the Gulf and Atlantic coasts while being dragged to their deaths in shrimp nets.
For fishing boats, the numbers are more elusive, but Allman points to research that shows that worldwide, 85,000 sea turtle bycatch deaths occurred over a 20-year period. However, that study only represents less than 1% of the total fishing fleet around the world, Allman said, “so that number could be astronomically higher.”
The bottom line, he says, is that magnitude of sea turtle bycatch is unsustainable and driving sea turtles closer to extinction.
He worked with Ghanaian fishers to add soda can-sized lights at 10- to-15-meter intervals along their nets’ borders, an easy, low-cost fix that’s been used by commercial fleets, but had never been tried with small-scale fishers.
It worked. After two different studies in two separate fishing communities, the experimental nets with lights captured 82 and 81% fewer turtles than the control nets minus lights – “both incredibly high values,” he said.
The weakened federal rule targeted by the nonprofits exempts turtle excluder devices on vessels smaller than 40 feet, which will result in an estimated 1,300 preventable sea turtle deaths from smaller vessels each year, the conservation groups say.
Any efforts to reduce bycatch turtle deaths would help. Sea turtles are highly migratory, routinely crossing the Atlantic and Pacific oceans. “These turtles move around a lot … moving from foraging habitat to breeding grounds,” he said.
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The benefit of such research as Allman's is that it's applicable in other places. “We can study populations, specific threats and try to develop tools such as this to reduce their mortality, and that tool will likely work in other locations as well.”
Whether LEDS would work for shrimp trawlers, in which pouch-shaped nets are dragged along the ocean floor, “I’m not sure the light would prevent a turtle from moving into the net but maybe it’s worth experimenting with to see," he said. "The only way for these species to recover their population is to work with fishermen and work with industry to find solutions to the bycatch issue."
For ordinary citizens who want to help, Allman recommends engaging with area restaurants and fishmongers.
"One thing the public can do is find out where their fish came from and try to purchase fish locally captured. Just ask the server if they know where the fish is from and if the server doesn’t know, ask if they can find out from the manager.”
If everyone does it, Allman says, it’ll become the norm, not just helping to support area fishing families and businesses, he says, but “Here in Florida it helps support a fishery that is much more tightly regulated (with) much less ecological damage … Instead of buying fish caught with unsustainable methods halfway across the globe, it’s better for the fisheries and it’s better for sea turtles if they buy fish captured locally.”