Fishing and Gear Technology

Unit 13 - Gillsnets

13. Gillnets

A gillnet consists of a long, rectangular web of netting with head rope, footrope, floats and sinkers are fixed on it, which is set in the water to form a vertical wall. Gillnet can be set on the bottom, in midwater or at the surface. Fish are caught in gillnet in one of the three ways.

• Wedging: The fish is held tight around the body of the mesh.
• Gilling: The fish enters the net but it is too large to pass through the mesh and it is prevented from retrieving by the twine that has caught the fish behind its gills.
• Tangling: The fish has not necessarily penetrated a mesh but caught to maxillaries or other projections.

Gillnet selectivity is mainly influenced by its mesh size, but other factors like twine and gear design and environmental factors are also have some influence. Capture by gilling, wedging and tangling is dependent on the shape of the particular species of fish encountered. Besides its well known size selectivity properties, gillnets are therefore also species selective.
Fishes are commonly caught in a gillnet are by wedging and gilling. The smallest fish caught has a maximum girth equal to the perimeter of the mesh and the largest fish caught has a head girth equal to the perimeter of the mesh. There is an optimum size at which a fish is most likely to be entangled in the net. Fish that are smaller or larger than this optimum size but within the capture range are less likely to captured.