Longlines

Longline fishing is a commercial fishing technique that uses thousands of baited hooks hanging from a single line, often miles long. Swordfish, tuna and mackerel are commonly targeted by this fishery. Longlines can be set to hang at varying depths depending on the targeted species. Leatherbacks, being primarily a pelagic species, are especially threatened by this method of fishing.
 
Longlines catch a large amount of bycatch because the baited hooks provide an easy meal for any indiscriminant predator, including sea turtles. Endangered sea turtles will commonly swallow baited hooks or become hooked in the mouth or other areas of the body. Longlines are often set in the water for extended periods of time. By the time they are removed from the water, the hooked turtles have drowned. There are methods for disentanglement from fishing line and the removal of hooks from the turtles, but the process can be time-consuming, complicated and even dangerous because of the size of the turtle. It is not clear how many turtles are released from longlines still hooked or entangled and how many are removed from longlines using proper de-hooking methods.
 
The use of circle hooks can significantly reduce the number of hooks that are deeply or lethally ingested by turtles. Unlike J-hooks which tend to be swallowed by sea turtles as they ingest the baited line, circle hooks tend to snare turtles in the beak. A turtle that has had a hook removed from its beak is much more likely to live than a turtle that has fully ingested a hook. The use of circle hooks could significantly decrease the number of post-hooking mortalities for sea turtles.