Destructive Fishing Practices

There is no overall agreed upon definition of destructive fishing practices but generally it involves methods of fishing that cause destruction to the habitat or ecosystem in addition to catching the desired species. Every type of fishing gear has an effect on the ocean and many techniques can be destructive.

As worldwide fish numbers decrease, fishing methods have been more and more extreme. Some practices devastate the surrounding environment causing irreversible damage.

Some of these practices are illegal in some parts of the world. However, they are often not adequately enforced.

The ocean and its inhabitants are under so much pressure from other sources, including overfishing. With a worldwide reduction in fish stocks alongside the food needs of growing populations, for humanity to cause further destruction to the ocean, is irresponsible. Fishing is not the problem, but careless destruction while fishing is unnecessary. Below are some of the negative impacts of destructive fishing practices.

Habitat Destruction

  • Huge nets or metal structures dragging along the seafloor are capable of destroying enormous areas of marine habitat. Coral reefs are particularly vulnerable, including deep sea, and cold-water coral species. While sandy bottoms and rocky environments can regenerate quite quickly, coral ecosystems and sponge gardens can take decades, if not longer, to be restored. Crushing is not the only impact, sediment suspension, changes in water chemistry, and changes to marine life all have lasting effects on the ecosystem.
  • Fishing methods involving explosives, usually used on or near shallow reefs cause immediate and permanent damage.
  • The use of chemicals to stun and capture fish will damage and kill the coral reef as well as surrounding animals and plants, including seagrass beds. Further, when fishermen attempt to collect the stunned fish, they often break corals in the process.

Bycatch is the name for the unwanted fish or other marine creatures inadvertently caught while targeting another species. Fish to be sold are kept while the rest are usually discarded at sea, often already dead or dying. Depending on the method of fishing, many different marine species can be caught as bycatch, many of which are threatened or endangered (fish, sea turtles, sharks, manta rays, dolphins, and even seabirds). Many destructive methods of fishing are unselective (huge nets, miles of fishing lines) and result in massive amounts of bycatch (up to 60% in some cases). Hundreds of thousands of cetaceans and sharks and rays are killed each year globally by commercial fishing methods.

Ghost Nets
Lost or abandoned fishing gear, especially large nets, continue to float in the open ocean entangling and killing marine life; this is referred to as “ghost fishing.” When smaller fish get entangled, they attract larger fish, who themselves can become entangled and eventually starve. Sea turtles and sharks risk suffocation as well as starvation. Abandoned nets can also entangle and suffocate coral reefs if waves direct them to shallower waters.

Reductions in Fish Populations
Large percentages of bycatch from indiscriminate fishing methods can be juvenile fish. The loss of non-reproducing animals threatens future fish populations. Further, when habitats are destroyed in the fishing process, the productivity of the ecosystem is diminished through the loss of feeding, breeding, and nursery areas.

Global Warming
Recently, the climate impacts of the destruction of the sea bed have been analyzed. Since carbon is naturally stored as sediment on the seafloor, when this is disturbed, carbon dioxide is again released into the ocean. The amount released globally exceeds annual CO2 emissions from global aviation!

While most any method of fishing can harm the ocean if done improperly or excessively, these are some examples of particularly destructive practices.

Bottom/Midwater Trawling
Trawling is an industrial fishing method in which a large net with heavy weights is dragged across the seafloor or through the water column. It is a very efficient method of catching fish as everything in the path of the net is caught. Trawling can involve one boat pulling the net or two boats pulling either end of a larger net. These nets can be massive, up to 1.6km long (nearly a mile) with an opening of 60x120m (approximately 200×400 feet). Some of these nets can hold ten 747 jumbo jets! Bottom trawling is estimated to account for 25% of the worldwide industrial catch as they scrape 14% of the seabed annually. Trawling is responsible for seabed habitat destruction as well as large amounts of bycatch.

Longlining is a fishing technique involving thousands of baited hooks hanging from fishing lines that can be 30-60 miles (40-80km) long. Longlines can be set close to the surface or at varying depths depending on the targeted species. Globally, the longlining industry sets 1.4 billion hooks every year from lines that could encircle the planet more than 550 times! Swordfish, tuna, mackerel, snapper, and grouper are fish commonly caught with longlining. Bycatch percentages in longlining vary depending on the target species (which affects the depth of the lines), however, sharks and turtles are often caught as well as seabirds.

Chemical Fishing
Some fishing practices, especially for the aquarium trade involve the use of chemicals such as cyanide or bleach to poison and stun fish. Not only does this kill surrounding plants and animals, but between ⅓-½ of all targeted fish die soon after making this particularly destructive.

Blast/Dynamite Fishing
This practice involves the use of explosives, dropped into shallower water, to kill or stun fish which then rise to the surface. Habitat destruction after repeated blasts is complete with large sections of reef completely destroyed.

Gillnets/Drift Nets
A gillnet is a wall of netting that hangs, usually from buoys, midwater trapping anything that swims directly into it. Since a large boat isn’t required, gillnets are often used in less developed areas. Drift nets are similar but drift with the current until they are collected. Gillnets are responsible for high levels of bycatch.

Dredging, an industrial fishing practice, is similar to bottom trawling. In this case, a metal structure is dragged along the floor in order to detach bivalves (scallops, oysters, and clams) from the bottom of the seafloor. Like bottom trawling, dredging can tear up the sea floor habitat and entrap or crush any bottom dwelling marine life.

Muro-ami is a small-scale fishing method used on coral reefs in Southeast Asia. A net encircles a section of reef and stones or other heavy objects smash the surrounding corals, scaring the fish out of their reef hiding places and into the net. Obviously, this causes a great deal of reef habitat destruction.

As a consumer, you have the ability to research the source of your seafood to support companies that are environmentally responsible. The amount of impact we can personally have on the commercial fishing industry may be minimal, but we have control over our individual choices and spending habits.

Educate Yourself on the Source of Your Seafood
Whether at the supermarket or a restaurant, consider not only the type of seafood you choose, but also the source. What methods were used to catch it? Ask for information and expect the store or restaurant to know. Seafood guides like Seafood Watch, Ocean Wise Seafood Search and the Good Fish Guide can help. Avoid supporting fisheries using destructive methods.

Buy Fresh Fish
Although fresh fish (rather than frozen) may be more expensive, this decreases the demand for fish caught in a destructive manner.

Support Regulations on Commercial Fishing
Demand an end to destructive bottom trawling, especially in environmentally sensitive areas. Push for bans on trawling during spawning season. Encourage requirements for gear modifications that reduce contact between nets and the seabed. Encourage restrictions on the size of nets used to reduce the capture of juveniles.

Support Organizations Working to End Destructive Fishing Practices
Some organizations are mapping and monitoring fishing areas to ensure protection of environmentally sensitive habitats. Some are pushing for increased protection of deep-sea habitats, many of which have not yet been mapped. Others are working to educate local communities on the impact of destructive methods of fishing and encouraging change. Still others focus on enforcement of existing laws against destructive fishing.

Many organizations are working to end industrial and artisanal destructive fishing practices around the world. Education, monitoring, consumer responsibility and enforcement are key. Learn more below.

Global Fishing Watch
Inland Ocean Coalition
Marine Conservation Society
Save the Whales

Coral Reef Rehabilitation and Management Program, Indonesia
This program aimed to introduce marine protected areas and introduce conservation to smaller provincial governments in Indonesia. The emphasis was on community-based coral reef management. Some fishermen who practiced destructive fishing methods (dynamite and cyanide fishing) in Sulawesi have not only stopped the practice, but now are conservation advocates in their communities. While Indonesia has laws against these practices, it is through local support and enforcement that real change is happening.

Trawling Ban, Isle of Man
In the coastal waters off the Isle of Man, great scallops were an important resource but, due to bottom trawling, were becoming scarce. In 1989, a small area was closed to bottom trawling. After 14 years of protection, scallops were 5 times more abundant and and 1200 times higher reproductive potential in the no-trawl zone.

Longline Fishing Ban, California, USA
In 2020, a new federal ruling banned longline fishing along the California coast largely to help protect highly endangered leatherback sea turtles. The Center for Biological Diversity and Turtle Island Restoration Network filed suit, and won, against the National Oceanic and Atmospheric Agency to stop permits for longline fishing.

Rockfish Species Recovery, West Coast, USA
Two decades ago, bottom trawling was banned in large sections of the Pacific Ocean to protect the dwindling rockfish population. Now, as the species is rebounding (50 years faster than predicted), fishermen and environmental groups have worked together to allow the return of trawling, with some restrictions. Areas with deep-sea corals and sponges as well as areas essential to fish reproduction will remain off-limits.