October 20, 2026 — Depredation, the removal of or damage to hooked fish or gear by sharks or other marine predators, is a growing concern among fishing communities. Depredation results in increased mortality for managed fish stocks, economic loss, and degraded fishing experiences.
NOAA Fisheries biologists Dr. William “Trey” Driggers and Dr. Walter Ingram recently analyzed data from the Southeast Fisheries Science Center’s Bottom Longline Survey. Their goal: to determine trends in depredation rates over the past two decades. This is one of the first fishery-independent analyses of shark depredation—most research has been conducted in the fishery. The data confirm what anglers are seeing on the water: increasing trends in depredation by species like sandbar, blacktip, bull, and tiger sharks.
History of the Bottom Longline Survey
The annual Bottom Longline Survey, which started in 1995, samples U.S. waters of the Atlantic Ocean, including the Gulf of America, from Brownsville, Texas, to Cape Hatteras, North Carolina. Scientists use these data to monitor trends in abundance of federally managed sharks and other fish species like red snapper. It provides fishery-independent indices of abundance for numerous federal stock assessments in the Southeast region. When the survey protocol was standardized in 2001, Dr. Driggers recognized the importance of collecting data on depredation events. He added it as a standard data collection metric for the survey.
Since 2005, the survey has collected data on:
- Whether depredation occurred
- Predator species preying on the hooked catch, when possible
- Species of the depredated catch
- Variables like location, depth, temperature, and salinity
This has resulted in a standardized record of depredation events for all survey longline sets for more than two decades.