Longlines consist of a mainline, gangions, and baited hooks.
A high-flyer buoy is used to monitor gear position while fishing, and lightsticks are often used to target certain species. The longline set can be suspended at any depth within the water column, depending on target species.
- Hook type varies with different catch species, but J-hooks and circle hooks are most common. Circle hooks are required in Atlantic pelagic longline fisheries.
- Once deployed, sets can soak for hours.
- Bait includes squid, mackerel, and sardines.
- The average U.S. longline set is 28 miles (45 km) long. There are limits on longline length in areas.
- Longline fisheries range from local small-scale operations to large-scale mechanized fishing fleets.
Target Species
- Tuna
- Swordfish
- Other Pacific billfish
Fisheries Regions
Throughout U.S. waters, including off Alaska and Hawaii.
Risks to Sea Turtles
High numbers of sea turtles are incidentally caught in longline fisheries worldwide.
Lightsticks may attract sea turtles to the baited hooks.
Loggerheads and leatherbacks are the species most commonly captured as bycatch.
A hook can penetrate the turtle's flippers, head, mouth, or neck. If a turtle swallows an entire hook, it can become lodged in the turtle's digestive track, thereby hindering normal feeding and digestion, resulting in starvation and possibly death.
Entanglements may lead to severe lacerations and infections caused by constriction of the lines on the turtle's soft body.
- Loggerheads are most often hooked in the mouth or esophagus.
- Leatherbacks are commonly hooked around the front flippers.
- Turtles entangled or hooked at depth likely drown because they cannot reach the surface to breathe.
Risks to Marine Mammals
Marine mammals are often entangled or hooked in longline gear.
Pilot whales and false killer whales are known to steal bait and or target catch from longlines and can thus be hooked in the mouth or entangled in the lines.
Risso's dolphins, bottlenose dolphins, and several species of whales have also been documented as longline bycatch.
Injuries from these interactions can include lacerations, puncture wounds, exhaustion, and drowning.
Bycatch Reduction
Current bycatch reduction measures include the use of circle hooks, with the shape and smaller opening reducing the likelihood of turtles and marine mammals ingesting hooks or being caught. When hookings do occur, they are superficial and primarily in the mouth, which reduces internal injury and allows for safer release. Circle hooks used in combination with finfish bait like mackerel significantly reduce sea turtle bycatch.
Other measures can also reduce the number and severity of marine mammal interactions:
- Minimizing soak times.
- Limiting mainline length.
- Following safe handling and release protocols.
- Encouraging captain communications.
- Researching dolphin and whale feeding behavior to identify how they become hooked in the gear.
More Information
Leatherback turtle in the Kei Islands. Credit: Scubazoo/Jason Isley
A hawksbill sea turtle swimming above a coral reef in western Maui in the Hawaiian Islands. Credit: NOAA Fisheries/Don McLeish. Photo taken under permit #21260.
The Pacific leatherback sea turtles have existed in their current form without scales and a hard shell since the age of the dinosaurs, but threats from bycatch, egg harvesting, and degradation of nesting habit have made this species endangered. Photo credit: Jason Isley, Scubazoo.