Shrimp trawling: a threat to the marine environment

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There have been many methods of catching fish, shrimp, and other aquatic species from the past to the present. All of them are based on man’s realization that the sea is a source of food for him. Fishing has a long history and is one of the main sources of income for small coastal communities.

The depletion of marine resources through overfishing has been a concern in recent years. Fishing methods and gear, and the damage and risks they pose have been studied and researched by environmentalists and conservation groups to find solutions to minimize these risks.

Today, trawling is one of the most common ways of catching shrimp in the world. According to the available statistics, approximately 60% of shrimp are caught by trawling. This is a worrying statistic because trawling has many disadvantages for the marine environment and its overuse will lead to the destruction of the ecosystem.

Trawls are large, funnel-shaped nets made up of several parts: boards, bodies, wings, and ropes. The trawl net is thrown into the sea by vessels called trawlers, and fishing is done by pulling the net. Let’s look at some of the dangers of trawling together.

By-catch:

Trawls are designed to catch their target species but are so powerful that they catch everything in their path. This is called bycatch. Simply put, bycatch is the catch of non-target species. The number of aquatic animals caught as bycatch is greater than the number of target species, i.e., shrimp. In addition, a large percentage of bycatch consists of non-commercial fish that are returned to the sea by fishermen. A large proportion of these aquatic animals are immature and small fish. They die after being thrown back into the sea.

In recent years there have been changes in trawl design that have increased bycatch. For example, mesh sizes have been reduced and the type of twine used has been changed.

Bycatch has a destructive effect on the marine ecosystem. Bycatch is considered a serious threat to the sustainability of the environment by reducing the diversity of aquatic life, disrupting species relationships, and disrupting the food web.

In addition to bycatch, trawling has other direct and indirect impacts on the marine environment, which are discussed below.

Damage to coral reefs:

Damage to coral reefs on the ocean floor is one of the direct effects of trawling. Many coral reefs are destroyed each time a trawl is set. Statistics show that trawling destroys 20 to 25 percent of seafloor habitat.

Destruction of aquatic biomass:

Trawl nets penetrate deep into the seafloor due to their high power. During trawling, between 6 and 41 percent of the aquatic biomass on the seafloor is pulled up by the net. This amount is influenced by factors such as the duration of trawling, the type of trawl, the water depth, and the type of seabed. It can take one to six years for this biomass to regenerate.

Disturbance of infauna habitat:

Infauna refers to a group of creatures that live in the sediments of the seabed; therefore, they are not directly affected by fishing gear. However, they are threatened by the impact of trawl nets on their habitat.  The trawl net is stretched across the seabed. This disturbs the sediments and the habitat of the infauna, and their habitat is disrupted.

Trawl fishing also destroys micro-algae, suspends bottom sediment, reduces benthic life, upsets the marine ecological balance, kills bottom invertebrates, alters species composition, and reduces species diversity.

what should be done?

Now that the destructive effects of trawling on marine ecology have been identified, the question is: what should be done?

Management measures are an important part of the strategies that can be used to minimize the risks posed by trawling. These include reforms in the design of trawl nets, information to fishermen about the consequences of trawling, quota fishing, temporal and spatial control of fishing, etc.

Implementing and using these solutions requires a lot of knowledge, equipment, and effort. However, conservation groups must take action because sustainability and environmental protection are at stake.

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