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Gillnets: 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.

A gillnet is a wall of netting that hangs in the water column, typically made of monofilament or multifilament nylon.

Mesh sizes are designed to allow fish to get only their head through the netting, but not their body. The fish's gills then get caught in the mesh as the fish tries to back out of the net. As the fish struggles to free itself, it becomes more and more entangled. A variety of regulations and factors determine the mesh size, length, and height of commercial gillnets, including area fished and target species. There are two main types of gillnets:

Target Species

Fisheries Regions

Risks to Sea Turtles

Gillnetting has been a major source of mortality for all sea turtle species.

Turtles encountering a gillnet can quickly become entangled around their head or flippers as they try to escape. Entangled turtles will drown if held under the water but have a higher chance of survival if they can reach the surface to breathe. The nylon can tighten around the turtle's soft body parts and cause deep cuts potentially leading to infections, limited movement, or complete loss of the limb. Limited use of appendages can impair a turtle's natural feeding, breathing, and swimming behavior.

Risks to Marine Mammals

Gillnets can entangle a wide variety of marine mammals.

Depending on the gillnet mesh size, animals can become entangled around their necks, mouths, and flippers. Entanglement can prevent proper feeding, constrict growth, or cause infection after many months. Marine mammals entangled in set gillnets can drown while those entangled in drift gillnets can drag gear for miles as they migrate and forage, leading to extreme fatigue. Species most commonly caught in gillnets include:

Bycatch Reduction

Many factors have been studied in trying to minimize incidental capture, including adding breakaway panels and changing net slack, mesh size, and set depth.

Current regulated mitigation measures include:

Additional Resources

Updated: February 18, 2014