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
Pair of bottlenose dolphins. Credit: NOAA Pacific Islands Fisheries Science Center/Lisa Morse.
A humpback mother and calf swimming off the West Coast. Credit: NOAA Fisheries/Ed Lyman. NOAA Fisheries Permit #14682.
Oceanic whitetip shark. Hawaiʻi longline fishermen use leaders to connect weighed branch lines and baited hooks. A new rule prohibits steel wire leaders in the Hawaiʻi deep-set longline fishery, starting May 31, 2022. The rule aims to increase the survival of hooked oceanic whitetip sharks caught as bycatch in the Pacific Islands region. Credit: Andy Mann
Right whale #3853 swimming north offshore of South Carolina on Jan. 20, 2011 with a series of fresh propeller wounds running across its back. The whale was observed 5 days previously offshore of Georgia without propeller wounds. It is unknown whether the whale survived its wounds or not, as it has not been re-sighted since. Vessel collisions are a leading cause of right whale mortality. Credit: EcoHealth Alliance (NOAA permit #594-1759).