BTT Discovers Florida Bonefish Spawning Site

Bonefish & Tarpon Trust scientists have successfully located and documented a bonefish pre-spawning aggregation (PSA) in the Florida Keys. The discovery is the first of its kind in Florida waters and the culmination of a years-long search that utilized acoustic telemetry and the historical knowledge of veteran fishing guides.

“This is a major discovery for the Florida Keys fishery,” said BTT President and CEO Jim McDuffie. “BTT has previously identified PSAs in several other countries, but Florida sites remained elusive—until now. By locating this PSA, our scientists will be able to learn more about where and how bonefish spawn in the Florida Keys, which is information critical to the sustained recovery of the population.”

Over the course of the 2022-2023 bonefish spawning season, which spans from October to April, BTT Florida Keys Initiative Manager Dr. Ross Boucek and his team tracked 67 fish and logged more than 94,000 detections. Many of these detections were in the area where BTT research during the 2021-2022 season and reports from fishing guides indicated a likely PSA. Fourteen bonefish detected at the suspected PSA site had been tagged at distant flats, including two fish tagged 55 miles away.

The newly discovered PSA comprises approximately 2,000 to 5,000 fish and is located three to four miles offshore along a reef. Previously documented PSAs in the Bahamas and Belize are located in nearshore waters.

“It is encouraging to see that our bonefish population in Florida has recovered to a point now where big spawning aggregations can form,” said Boucek. “It’s our job to make sure that these fish can keep spawning for years to come. We can do this by protecting the habitats that support these aggregations, reducing human stresses from boat traffic and other on-water activities that could disrupt their spawn, and most importantly improving water quality. Harmful contaminants in the water have been shown to affect fish reproduction. We will continue to let science lead the way by determining what actions need to happen to keep bonefish spawning safe and happy.”

At the site, BTT scientists also observed bonefish gulping air at the surface. Previous research shows that bonefish engage in this behavior before spawning to fill their swim bladders. At night, the fish dive hundreds of feet and rapidly ascend to the surface. The sudden change in pressure during the ascent makes their swim bladders expand, enabling the bonefish to release their eggs and sperm. After fertilization takes place, the hatched larvae drift in the ocean’s currents before settling in shallow sand- or mud-bottom bays, where they develop into juvenile bonefish.

“As a Keys fishing guide for 53 years, with a science background, I took bonefish for granted—they were what I fished for every day,” said Captain Rick Ruoff, member of the BTT Board of Directors. “I thought that I knew all about the resource; until the population crashed. I discovered neither I, nor anyone else, knew where or how bonefish spawned—a major gap in our knowledge. BTT has come up with the amazing science to determine the dynamics of bonefish spawning. It has been a great lesson to me that we have located this missing piece of the puzzle. To have a healthy population and management goals, you have to understand all aspects of your resource. I am so proud to be part of the BTT science effort that has unraveled these bonefish mysteries, and will witness their rebound.”