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Bottom longline illustration.
Bottom longlines have a mainline weighted to the seafloor with buoy lines marked by flags on either end, called high flyers.
Leaders, called gangions or snoods, with baited hooks are attached to the mainline. A longline set can have up to a thousand baited hooks and once deployed can soak anywhere from hours to days.
Target Species
- Sharks
- Halibut
- Flounder
- Sole
- Other groundfish
Fisheries Regions
Used throughout U.S. waters, including off Alaska and Hawaii.
Risks to Sea Turtles
Many species of sea turtles feed along the bottom and can become entangled in branching gangions or may be atttracted to lightsticks attached near baited hooks.
A hook can penetrate the turtle's flippers, head, mouth, or neck. If swallowed, an entire hook can become lodged in the turtle's digestive tract, hindering normal feeding and digestion and possibly leading to starvation or death. Loggerheads are most often hooked in the mouth or esophagus while leatherbacks are commonly hooked around the front flippers.
Line entanglements can cause constriction of the lines on the turtle's soft body parts leading to severe lacerations and infections. Turtles entangled or hooked at depth likely drown because they cannot reach the surface to breathe.
Risks to Marine Mammals
Bottom longlines pose less of a threat from incidental hooking to marine mammal species that feed in shallower depths. However, injuries and entanglements can occur from vertical lines attached to surface buoys and in derelict gear. These interactions can lead to lacerations, puncture wounds, exhaustion from entanglement, and drowning.
Bycatch Reduction
NOAA Fisheries implemented regulations in 2005 to reduce bycatch in bottom longlines by requiring:
- Sea turtle release gear and handling instructions onboard reef fish vessels to facilitate the safe release of any sea turtles or smalltooth sawfish.
- Closures of certain fishing areas at certain times (time/ area closures).
- Fishing effort restrictions that limit the number of hooks per vessel.
Certain fisheries are also encouraged or required to carefully catalog and document bycatch through self-reporting and observer coverage in order to monitor the dynamics of incidental takes.
More Information
Humpback whales swimming underwater. Credit: Kogia.org
An endangered leatherback sea turtle swimming at the ocean surface. Once prevalent in almost every ocean, the leatherback population is rapidly declining in many parts of the world. As one of NOAA Fisheries’ Species in the Spotlight, we have made it a priority to focus recovery efforts on stabilizing and recovering the leatherback sea turtle to prevent its extinction. Photo credit: NOAA Fisheries
Gray whale breaching. Credit: NOAA Fisheries/Merrill Gosho.
A Rice’s whale just under the surface of the water in the Gulf of Mexico. This endangered whale was recognized as a separate species from the Bryde’s whale in 2021. Credit: NOAA Fisheries under NOAA Permit No. 21938.