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Bottom Longlines: Fishing Gear and Risks to Protected Species

NOTE: Gear types are listed by broad category. They are not intended to be specific to regional fishing practices.

Bottom longlines have a monofilament mainline up to a mile in length anchored on the seafloor at either end with buoy lines marked by flags, 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.

Credit: NOAA

Target Species

Fisheries Regions

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:

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.

Additional Resources

Updated: January 30, 2014