Gillnets: How They Work and Their Impact

Introduction:

Gillnets are a widely used fishing gear that have been in existence for centuries. They are commonly used in both commercial and recreational fishing to catch a variety of fish species. However, their use has also raised concerns regarding their impact on marine ecosystems and non-target species. In this article, we will explore how gillnets work, their importance in fishing, and the potential negative consequences associated with their use.

What are Gillnets?

Gillnets are vertical panels of netting that are suspended in the water column and designed to be nearly invisible to fish. They are typically made of monofilament or multifilament nylon or other synthetic materials. The nets are set in a way that allows fish to swim into them but prevents them from escaping. The mesh size of the net is chosen based on the target species and their size.

How do Gillnets Work?

When a fish swims into a gillnet, it attempts to pass through the mesh. As the fish tries to back out, its gills become entangled in the netting, preventing it from escaping. The more the fish struggles, the more entangled it becomes. Gillnets are often set in a way that they hang vertically in the water, creating a wall or curtain of netting through which fish must swim.

Selective Fishing:

In theory, gillnets can be highly selective, meaning they catch fish of a specific species and size while avoiding non-target species. Selectivity can be achieved by adjusting the mesh size, allowing smaller fish to escape while retaining larger ones. However, in practice, gillnets can still catch non-target species, including undersized fish and other marine animals such as marine mammals, seabirds, and sea turtles.

Impact on Marine Ecosystems:

One of the significant concerns surrounding gillnets is their potential impact on marine ecosystems. When gillnets are deployed, they can unintentionally catch and harm non-target species. This bycatch can include endangered or protected species, leading to population declines or even extinction in some cases. For example, sea turtles may become entangled in the netting, resulting in injury or death.

Gillnets can also have negative consequences for seabird populations. Birds diving into the water to catch fish can become entangled in the netting, leading to drowning or severe injuries. Seabirds, such as albatrosses, are particularly vulnerable to gillnets as they forage near the surface of the water.

Habitat Destruction:

Another potential impact of gillnets is habitat destruction. The nets can come into contact with the seafloor or other structures, causing damage to sensitive habitats such as coral reefs or seagrass beds. This can disrupt the functioning of the ecosystem and impact the species that depend on these habitats for their survival.

Ghost Fishing:

Gillnets can also contribute to a phenomenon known as ghost fishing. Ghost fishing occurs when abandoned or lost fishing gear continues to trap and kill fish and other species. These nets can remain in the water for extended periods, trapping and killing marine life indiscriminately. The entangled fish attract scavengers, which in turn become trapped themselves, creating a vicious cycle of death and destruction.

Management and Regulations:

Due to the concerns surrounding gillnets, many countries and international organizations have implemented management measures and regulations to mitigate their potential negative impacts. These regulations include restrictions on the size and mesh size of gillnets, as well as the use of turtle excluder devices and acoustic pingers to reduce bycatch of non-target species.

Alternative Fishing Methods:

In recent years, there has been a growing interest in developing and implementing alternative fishing methods that can reduce the ecological impact of fishing. These methods include the use of fish traps, which allow for selective fishing and reduced bycatch, and the adoption of sustainable fishing practices such as longlining, trolling, and pole-and-line fishing.

Conclusion:

Gillnets are a commonly used fishing gear that has both benefits and drawbacks. While they can be highly effective in catching target fish species, their use can also result in unintended consequences. Gillnets have been associated with high levels of bycatch, including the capture of non-target species such as sea turtles, seabirds, and marine mammals. They can also contribute to habitat destruction and ghost fishing. However, through the implementation of appropriate management measures and the adoption of alternative fishing methods, it is possible to reduce the negative impacts of gillnets and promote sustainable fishing practices.