Florida Tech researchers observe surprising bonefish spawning behavior in the Bahamas—with possible impacts felt across tropical marine life.

Bonefish, also called gray ghosts, are among the most elusive and highly prized fish sought by recreational anglers in the Florida Keys, Bahamas and similar tropical habitats around the world. Although bonefish support spawning waters off the Bahamian shoreline worth hundreds of millions of dollars annually, this fishery is threatened in many areas by habitat loss and overfishing. Scientists are scrambling to identify and protect critical habitats and identify other ways to conserve this vital fishery.

A recent study of bonefish spawning behavior brings to light new information that should aid bonefish conservation efforts. Aaron Adams, director of operations for Bonefish & Tarpon Trust (BTT) and research associate professor at Florida Institute of Technology, has shared the results with the Bahamas Ministry of the Environment and conservation collaborators Bahamas National Trust and The Nature Conservancy. He and other marine scientists sponsored by BTT, the nonprofit conservation group located at Florida Tech, recently tracked a school of more than 10,000 bonefish as they went through final stages of spawning in the Bahamas.

The implications are widespread, including in Tampa Bay. Although bonefish do not inhabit Tampa Bay, this research does impact the region’s fisheries. Ongoing research indicates that tarpon (which are related to bonefish) also undergo offshore migrations to spawn, and work is ongoing to identify these spawning locations so they can be protected. Also, this research is similar to recent research in Central Florida on snook that shows, like bonefish, they return to the same location to spawn each year. This means the future generations of these fisheries are reliant upon the continued good health of a few spawning locations.

The scientists found that, starting in mid-afternoon, the school swirled like a tornado in water 30 feet deep. These fish, which normally live on the bottom, started rushing to the surface to gulp air. Bumping against one another in a pre-spawning behavior, the fish tried to avoid the sharks, barracudas and Cubera snappers stalking the school. As night fell, fish in the school quickened their pace and headed for the drop-off at the edge of the reef, where water depths exceed 1,000 feet.

Using special tags they had inserted into the bonefish on a previous day, the team tracked the school as it quickly descended past 160 feet and drifted about a quarter mile from the edge of the drop-off. These shallow water fish were now suspended in the deep ocean, in water thousands of feet deep. After an hour in the deep, the bonefish suddenly rushed upward, releasing their eggs and sperm as they reached 80 feet below the surface.

The spawn over, the fish quickly moved back into shallow water, and the school was gone by the next morning, headed home. Ongoing tracking of bonefish is also revealing exciting new information—that bonefish are migrating 70 miles or more to get to this spawning location, and then reversing course to head home. At the spawning site, they left behind millions of fertilized eggs drifting in the water and beginning a two-month larval stage that will ideally result in baby bonefish somewhere in the Bahamas to begin the cycle again.