Q: While fishing off Fowey Lighthouse south of Miami, Florida, in about 800 feet of water, we caught this weird-looking shark with a long tail. The fish measured over 17 feet in length and weighed 584 pounds. I believe it is a thresher shark. But my questions are, What kind of thresher is it, and do these sharks live in the depths of the ocean worldwide or just in the Florida area? We have caught five more in this area since then. --Dan De Bonis, Miami, Florida
A: That's quite a catch, Dan! Your fish is a bigeye thresher, Alopias superciliosus. This species can be distinguished from the other species of thresher sharks by its large, dorsally oriented eyes, the prominent groove that extends from the area just above and behind its eyes to the region above its gill slits, and the position of its dorsal fin relative to its pectoral and pelvic fins. Bigeye threshers inhabit tropical and warm temperate waters throughout the world, at depths ranging from the surface to over 500 meters. Some authorities believe that this species commonly lives deeper than other threshers and that its large eye helps it see in low-light conditions. Bigeye threshers are thought to reach lengths of approximately 18 feet, so yours was a very large one.
There's one thing you should be aware of prior to catching any more of these sharks. Because of their low replacement rate, slow growth and declining numbers, bigeye threshers, like several other species of sharks, are fully protected by the National Oceanic and Atmospheric Administration and may no longer be legally taken by anglers in the United States. You can find out more about the current federal regulations pertaining to sharks by visiting www.nmfs.noaa.gov/sfa/hms/recinfo.htm and www.publicaffairs.noaa.gov/releases2003/dec03/noaa03-r153.html.