Bonefish, also called gray ghosts, are among the most elusive and highly prized fishes sought by recreational anglers in the Florida Keys, Bahamas and similar tropical habitats around the world. Bonefish support a fishery worth hundreds of millions of dollars annually, but this fishery is threatened in many areas by habitat loss and degradation, and by overfishing.
A recent study of bonefish spawning behavior in the Bahamas brings to light new information that should aid bonefish conservation efforts. In meetings in the Bahamas Dec. 9, Aaron Adams, director of operations for Bonefish & Tarpon Trust (BTT) and biological sciences research faculty member, 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 scientists found that, starting in mid-afternoon, the school swirled like a tornado in water 30 feet deep (http://youtube/5KMGm39zOqI). These fish, which normally live on the bottom, started rushing to the surface to gulp air. Bumping against each other in a pre-spawning behavior, the fish tried to avoid the sharks, barracuda 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 previously, 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.
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-long larval stage that will ideally result in settlement of baby bonefish somewhere in the Bahamas to begin the cycle over again.
This new research effort led by Adams shows that thousands of bonefish can be involved simultaneously in spawning aggregations. It also documents new spawning-associated behaviors and identifies distinct staging and spawning locations.
These new observations help define conservation strategies required to maintain this vital fishery. The current research defines another critical need for conservation: protection of spawning aggregations. Bonefish spawning migration requires a greatly expanded conservation outlook that links critical deep and shallow habitats.
In addition to Adams, the research team included Jon Shenker, biological sciences; Andy Danylchuk, University of Massachusetts Amherst; and Zack Jud, Florida International University.