Longline Guidebook
By all appearances, sharks look hardy and it would be easy to assume that they can sustain long “soak times,” rough handling, or extensive exposure and still survive when returned to the sea.
But sharks have a few biological weaknesses that make them susceptible to stress and injury, which can reduce their chances at post-release survival.
Shark Anatomy
Most sharks must swim to breathe effectively, so long soak times in the water while attached to a hook could hinder their breathing. This causes stress—and in more extreme cases, suffocation—and reduces post-release survivorship.
Unlike other fish, these animals do not have a hard skeleton of bone to protect their internal organs. When out of water, the weight of gravity can tear their connective tissue, resulting in crushed or damaged organs. This same tissue holds the spinal cord in place, and for this reason, animals handled from the head or tail can suffer damage as a result.
A shark’s head also holds a number of sensitive and fragile organs used to detect prey, and if handling damages these, then the shark—once released—could be unable to locate prey and starve.
Handling and Hook Removal
Thus, considering these facts about shark biology, the handling techniques should be developed to minimize further injury to the animal (see for example Pacific Islands Regional Office (2022)). Of course, crew safety always is paramount, so employ these best practices only when they can be done safely and securely.
To release the shark as quickly as possible to increase its post-survivorship, it is recommended not to bring the shark on board.
- Thus, for sharks that are hooked or entangled, the use of long-handled line cutters and dehookers while the animal remains in the water is recommended.
- Bring the shark close to the vessel without putting much tension on the branchline and, if the hook is visible in the body or mouth, use a dehooking device or long-handled bolt cutter to remove the hook bard, and then remove the hook.
- If the hook is not observed, cut the line of the leader as close as possible to the shark’s mouth (and/or hook) leaving as little line/leader trailing as possible.
If the shark is brought on board, minimize the time to return it to the sea to increase survival and reduce the risk to the crew. As with sea turtles and seabirds, dehookers, bolt cutters, and line cutters can all be used to remove a hook, disentangle an animal or cut a leader if the hook is too deeply embedded as close as possible to the hook ring.
See the following galleries about general do’s and don’ts when handling the animal on deck.
