Surrounding net

Salmon purse seining

Surrounding net is a fishing technique that involves encircling a school of fish with a net. This method is widely used in commercial fishing to capture large quantities of fish efficiently. The technique is also known by various other names, including purse seine, ring net, and encircling net. The surrounding net method is particularly effective for species that school, or gather in large groups, such as tuna, mackerel, and sardines.

Overview

The basic principle of the surrounding net technique involves a fishing vessel deploying a large wall of netting into the ocean. The net is laid out in a circle or semi-circle around a school of fish detected by sonar or spotted by a spotter plane. Once the fish are encircled, the bottom of the net is drawn together, similar to a drawstring bag, to prevent the fish from escaping by diving deeper. This process is known as "pursing" the net. The entire encircled mass of fish is then gradually drawn towards the vessel and hoisted aboard.

Equipment

The key piece of equipment used in the surrounding net method is the seine net. Seine nets are large nets with floats attached to the top edge to keep them vertical in the water and weights on the bottom edge to ensure they sink. The size and type of net used can vary significantly depending on the target fish species and the size of the vessel. In addition to the net, modern fishing vessels equipped for this method often use sophisticated sonar and radar to locate schools of fish. Some operations also employ spotter planes to find fish from the air.

Environmental Impact

While the surrounding net method is efficient for capturing large quantities of fish, it has raised environmental concerns. The primary issue is bycatch, the capture of non-target species, including juvenile fish, dolphins, and sea turtles, which can be significant. Efforts to mitigate bycatch have led to the development of devices such as the Bycatch Reduction Device (BRD) and modifications to fishing techniques.

Another concern is the potential for overfishing, as the efficiency of surrounding net fishing can lead to the depletion of fish stocks if not properly managed. Various international and regional organizations regulate the use of surrounding nets and the total allowable catch to help ensure sustainable fishing practices.

Regulation and Management

The regulation of surrounding net fishing is critical to preventing overfishing and minimizing environmental impact. Various international agreements and national regulations govern the use of surrounding nets, including limits on the size of the nets, closed seasons, and restrictions on fishing in certain areas to protect vulnerable ecosystems and species.

Conclusion

Surrounding net fishing is a highly effective commercial fishing method that, when managed and regulated properly, can be part of a sustainable approach to exploiting marine resources. Ongoing research and technological advancements aim to further reduce the environmental impact of this fishing technique, ensuring the long-term health of the world's fish stocks and marine ecosystems.

Surrounding net Resources
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