By Katie Keil
Two stories seem to circulate repeatedly in the news: declining sea turtle populations and the dangers of fishing to marine life. Unsurprisingly, the two are related.
Fishing gear is the single greatest threat to sea turtles. Bycatch, or the incidental capture of a species by a commercial fishery, is such an extensive problem that some small-scale fishing boats can catch 16 sea turtles a day. Even more staggering: each year, over “250,000 sea turtles are accidentally captured, injured, or killed by U.S. fishermen” alone.
In order to monitor species vulnerability, the International Union for Conservation of Nature (IUCN) established the IUCN Red List, a global conservation tool designed to assess species conservation status. All seven extant sea turtle species have made troubling appearances on the Red List due to the consequences of bycatch and issues pertaining to habitat loss, coastal development, overharvesting, and pollution. Loggerhead, Leatherback, and Olive Ridley turtles are currently listed as vulnerable; Green are endangered; and Kemp’s Ridley and Hawksbill are critically endangered. Flatbacks were previously listed as vulnerable but are now “data-limited”. While it has taken years of declining populations to increase protections, nations, governments, and locals are joining together to fight for sea turtle restoration—and are gaining ground.
Increased pressure for fishery regulation has led to an outstanding 90% reduction of sea turtle bycatch in the US since the 1990s. Successful bycatch mitigation techniques include spatial and temporal closures, inspection programs, circle hooks, large mesh nets, dehooking equipment, and turtle excluder devices.
Additionally, recent research on sea turtle behavior has paved the way for innovative methods of reducing bycatch. Artificial light has traditionally played a detrimental role in sea turtle conservation because hatchlings follow the lights of coastal development instead of the instinctual bright ocean horizon promising safety. The tides turned, however, when we learned that sea turtles follow distinct visual cues when foraging for food and are deterred by certain wavelengths of light.
Using this information, researchers found that by simply adding LED lights to fishing gear, sea turtle bycatch rates dropped 40%. These visual deterrents act as a warning signal for sea turtles, prompting them to avoid the nets altogether. Similarly, adding chemical lightsticks reduced bycatch rates by 60%— a development that, if implemented on a large-scale, could save thousands of sea turtles annually.
Even more promising is that the fishery’s target species were largely unaffected by the lights, maintaining catch value and, consequently, the fishery’s profits. By using these lights, some fishermen have even experienced increased yields while others have seen a 90% decrease in bycatch of other marine species. This technology has the potential to save fishermen time, money, and effort spent removing unwanted species from their catch and fixing holes in their nets. Since both sea turtles and fishermen are benefiting, the lights are more likely to be accepted by fisheries, making it a notable victory for conservationists.
While these innovative, low cost, and easy to maintain strategies aren’t a “silver bullet” for conservation, they are a significant achievement in the fight to preserve our ocean’s biodiversity. Overall, these lights, coupled with other conservation strategies, illuminate the way to a happier and healthier ocean.