You will find gill nets most commonly in commercial saltwater applications. These nets are used much like vertical traps in the water. As fish swim through the nets, the size of their bodies prevents them from progressing. When attempting to back out, their gills are caught in the net, effectively keeping them in place. This allows non-target fish smaller than the desired species to swim through the mesh unharmed, while it only traps larger fish by their gills. Nevertheless, there are some concerns about the effects of gill net fishing on the environment.
Gill Nets Result in Highly Selective Catch Makeup
Gill netting is a very cost-effective means of fishing for a target species. You can eliminate the need for sorting your catch simply by adjusting the size of the mesh to only trap the animals that are the approximate fish size. Unlike trawl fishing, there is no need for specialized fishing vessels to haul in the catch. The United Nations' Food and Agriculture Organization considers gill nets to offer fishermen the opportunity for low-energy fishing.
Another advantage of gill net fishing is the preservation of younger or undersized fish. This ensures the continued presence of the target species in the waters that are fished.
Gill Netting Impacts Tourism
Sea Watch reports that Baja California and the islands in that region experience adverse effects from gill netting. Small-time commercial fishermen leave their own over-fished fishing grounds in search of new areas for catching fish. In the areas around Santa Cruz and San Jose, they set up their nets and quickly catch reef fish. Since the fish are the dominant species in these areas, fishermen may employ this method of fishing more than once per day. This leads to a record depletion of fish, which in turn causes tourists intent on snorkeling, fishing, and reef diving to visit other locales where nature is still untouched and fish are plentiful. This adverse impact on tourism may cause the impoverishment of coastal areas.
Gill Nets May Become Ghost Nets
A ghost net is a fishing net that has loosened and floated away. This may be due to a storm, or it may happen as pollution, when a damaged gill net is disposed of by throwing it overboard. Although no longer in active use for commercial fishing, the net still has the potential to entrap fish and other marine life. It is not unusual to find sea turtles or dolphins entangled in ghost nets. Since the nets are unmonitored, the animals may not be able to untangle themselves, and gradually either starve to death, become easy prey for other species or suffocate from a lack of oxygen. Although these are effects of unintentional gill net fishing, they nonetheless contribute to the overall effects the use of this netting has.