How can large mesh fishing nets improve selectivity while reducing the accidental capture of juvenile fish?
Publish Time: 2026-01-05
Against the backdrop of increasingly strained global fishery resources and the degradation of marine ecosystems, sustainable fishing has become an industry consensus. While traditional fine-mesh fishing nets can increase the catch per run, they inevitably capture large numbers of juvenile fish that are not yet of reproductive age, severely damaging the population's regeneration capacity. Large mesh fishing nets, as a fishing tool designed based on eco-friendly principles, are effectively protecting juvenile fish resources while ensuring fishermen's economic benefits through their physical screening mechanism, becoming a key technological means to promote sustainable fisheries development.
1. Physical Screening Mechanism: Achieving Natural "Access" Control through Mesh Size
The core principle of large mesh fishing nets lies in passively screening by utilizing the size difference between target fish and non-target individuals. When the net is dragged or stationary in the water, smaller juvenile fish can freely escape through the mesh, while adult fish of marketable size are effectively preserved. For example, for adult cod, which generally exceeds 30 cm in length, using a mesh size of 120 mm or more can allow more than 90% of juvenile fish to successfully escape. This "size selectivity" requires no additional energy or complex operations; it achieves resource classification solely through the net structure itself, reducing ineffective bycatch at the source.
2. Scientifically Designed Mesh Size: Balancing Ecological Benefits and Fishing Efficiency
Larger mesh sizes are not necessarily better. Excessively large meshes may increase the miss rate of target fish species, impacting fishermen's livelihoods; too small meshes, on the other hand, lose their protective significance. Therefore, fisheries management departments in various countries typically establish legal minimum mesh size standards based on the minimum catchable body length, cross-sectional dimensions, and swimming behavior of target fish species. For example, the EU stipulates that bottom trawl meshes must not be less than 120 mm, while China requires shrimp trawl meshes to be no less than 54 mm in some sea areas. Scientifically designed large meshes ensure effective capture of adult fish while providing ample escape routes for juvenile fish, achieving a win-win situation for both ecology and economy.
3. Reduced Bycatch and Seabed Disturbance, Enhancing Overall Operational Sustainability
In addition to protecting juvenile fish, large mesh designs can significantly reduce the bycatch of non-target species, minimizing biological waste caused by "bycatch and discard." Meanwhile, the increased mesh size enhances water flow penetration, reducing resistance during towing and thus lowering fuel consumption for fishing vessels. It also minimizes disturbance to seabed sediments and reduces physical damage to benthic ecosystems. This "light footprint" fishing method aligns better with the development direction of modern green fisheries.
4. Material and Structural Optimization: Ensuring the Practicality and Durability of Large Mesh Fishing Nets
Some worry that larger mesh sizes will weaken the net's strength. Large mesh fishing nets are often woven from high-strength, low-density synthetic fibers such as ultra-high molecular weight polyethylene. These materials have a tensile strength 15 times that of steel wire and are corrosion-resistant and UV-resistant. Even with larger mesh sizes, the overall structural stability remains superior to traditional nylon nets. Furthermore, by optimizing knot patterns and strengthening cable design, the lifespan can be extended while maintaining selectivity, reducing replacement frequency and costs.
Large mesh fishing nets are not merely a simple tool improvement; they symbolize the transformation of fisheries from "depletion of resources" to "sustainable utilization." Using the most basic physical laws, they protect the most vulnerable life in the ocean—juvenile fish—leaving hope for species reproduction. Under the dual goals of ecological civilization and food security, promoting scientifically designed large mesh fishing nets is both a responsibility and a sign of wisdom. Only by allowing today's "fish that slip through the net" to grow into tomorrow's abundant catch can the ocean truly become humanity's inexhaustible blue granary.
