How does the mesh size of a hairtail net affect the capture rate of target fish species and the escape rate of juveniles?
Publish Time: 2025-08-21
The mesh size of a hairtail net plays a crucial role in fishing operations. It not only directly affects the efficiency of capturing target fish species, but also profoundly impacts the sustainability of marine ecosystems. As the most basic structural unit of a fishing net, the mesh size determines which individuals are retained and which escape through the mesh. This screening mechanism creates a natural "selective fishing" process in practice, and its effectiveness depends on whether the mesh design is well-suited to the biological characteristics of the target fish species.
As a slender, ribbon-shaped pelagic fish, the hairtail has a unique width-to-height ratio, which makes it pass through the mesh differently from fish with a more circular cross-section. When a hairtail enters a net while swimming, its body typically contacts the net sideways or at an angle. In this case, if the mesh size is similar to the widest point of the hairtail, the fish will have difficulty passing through it during its struggle, effectively becoming entangled or trapped. A mesh size that is too large may allow adult hairtail to slip through, reducing catch efficiency. A mesh size that is too small, while increasing catch rates, also carries a series of negative consequences.
While increasing the catch rate of target fish species, mesh size design must also consider the protection of juvenile fish. Juvenile fish are typically small and have soft bones. If caught in a mesh that is too small, they are easily crushed or rubbed to death in the net, and even if released, they are unlikely to survive. A mesh size that is appropriately large provides an escape route for these immature fish, allowing them to pass through the net smoothly after contact, reducing unnecessary losses. This "letting the small and retaining the large" mechanism is key to achieving sustainable utilization of fishery resources.
Furthermore, the actual effective mesh size of a net is not fixed; it is affected by net tension, water impact, and the strength of the fish's struggles. During hauling or trapping, the net is subjected to dynamic forces, and the mesh may stretch or deform, resulting in an increase in actual passing capacity. Therefore, the design must consider the elasticity of the material and the stability of the weave structure to ensure that the intended screening function is maintained under operational conditions. Nylon monofilament, with its excellent strength and moderate ductility, can maintain a relatively stable net shape under load, helping to improve the reliability of selective fishing.
From an ecological perspective, a reasonable mesh size not only protects juvenile fish but also helps maintain a balanced food chain. Overfishing of small individuals directly affects the reproductive potential of the population, leading to resource decline. Optimizing mesh size, however, allows the catch to focus on sexually mature, reproductive individuals, effectively maintaining the population's ability to regenerate. This scientifically managed fishing approach is gradually becoming the mainstream direction of modern fishery development.
Meanwhile, mesh design must be tailored to the specific characteristics of the fishing method. For example, in set net operations, the current pushes fish slowly towards the net, giving them more opportunities to attempt to pass through the mesh. In this case, a larger mesh size is more conducive to selective fishing. In trawling operations, however, fish are startled and quickly collide with the net wall, resulting in a shorter contact time. The effect of mesh size on escape rate is more complex. Therefore, a single mesh size standard is not suitable for all scenarios and requires flexible adjustment based on the specific operation method.
It's worth noting that the choice of mesh size is also subject to regulations and management policies. Many coastal countries and regions have issued fishing gear regulations, clearly limiting minimum mesh size to curb overfishing. While pursuing economic benefits, fishermen must also abide by relevant regulations and promote responsible fisheries development.
In summary, the mesh size of hairtail nets is not simply a technical parameter; it serves as a bridge between fishing efficiency and ecological protection. Through a physical screening mechanism, it ensures the effective capture of adult hairtail while providing a living space for juveniles. Scientifically sound mesh design reflects humanity's respect for and compliance with the laws of nature in its utilization of marine resources and is essential for the long-term and stable development of the fishery industry.
