Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Cast Nets

Kaneaki Edo

doi: https://doi.org/10.47886/9781888569926.ch7

The cast-net method for sampling freshwater fish is a small-scale method of net fishing that can be conducted by one person. With a relatively long history, cast-net fishing is regarded as a traditional method of catching fish that has been used since antiquity. Historians have discovered evidence of net imprints on ancient pottery and the presence of ancient floats and sinkers, indicating that the cast-net method of catching fish has likely been in use since the Neolithic Age.

A cast net is made up of three parts: the upper section (net band), the middle section (a conical-shaped net mesh), and the lower section, which is weighted. The practitioner casts using both hands and the shoulder, throwing the net onto the surface of water in an area likely to have the targeted fish. When hurled into the air, the net spreads out into a circular shape and expands; as the net hits the water surface, the weighted edges of the net descend into the water in a circular shape, spread out like a parachute, and trap the targeted fish within the circular section. Finally, when the weighted portions of the net reach the bottom of the stream, the top band of the net is pulled, cinching the net closed into a sacklike shape within the water. With the weights dragging along the stream bottom, the net is slowly drawn back to the caster’s hands, collecting the captured fish within the net. In most cast nets, the internal part of the lower section of the net (the section with rounded margins) forms a pouchlike structure in which the fish are caught. In deeper waters, where fish swim in or above the middle layer of water, the weights on the cast net’s characteristic conical shape (the cast net ring) and the purse line are pulled so that the net is quickly recovered by the caster in the water before the weights settle on the bottom of the stream. A light or bait is often used to attract the target fish into an area within the cast net’s range (Hayes et al. 1996).

Cast nets can be broadly classified into the three types: rapid current, deep water, and standard. Standard nets are the most common; they spread out into a conical shape when cast. In rapid currents or shallow sections of rivers and larger streams, appropriate-sized cast nets have a net length that is short in relation to the size of the mesh (see below for a discussion of mesh size). The mesh spreads out into the form of a plate when cast. The weights that are used are relatively light. Cast nets used in deep water have a longer net length in relation to the size of the mesh. Deepwater nets are designed in a campanulate (bell-shaped) form and spread out into a buglelike shape when cast. This type of net is often cast into deep waters and from riverbanks and stream banks and bridges.