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Commercial fishing methods

Updated: Jan 15

Commercial fishing is connected with many issues that it’s important to know about to make better, mindful and more educated choices when it comes to consuming seafood. In this article you can read about fishing methods we believe is good to avoid.

Longline fishing

Longlines are fishing lines up to 100km long with thousands of baited hooks

left in the water for hours or days. This method is usually applied for catching big predatory fish such as tuna, swordfish and mahi-mahi.

Photo credit: Graham Robertson (3)

But the same hooks are attracting other big predators as well. Many endangered species and sharks are accidentally caught on the longlines and as they can’t move, they drown within few hours.


Gillnets are large vertical panels of nets that hang from a line with floaters. The bottom line of the net is weighted to keep the net straight down. By altering the ratio of floats and weights, the net can be set to fish at any depth in the water.

Photo credit: Brian Skerry (3)

Gillneting has one of the highest rates of bycatch. Marine mammals, seabirds, sea turtles, sharks and rays are all captured in gillnets as bycatch. Depending on the gillnet mesh size, animals can become entangled around their necks, mouths, and flippers.

Bottom trawling

Bottom trawling is a method that uses huge nets that are weighed down and dragged along the sea floor by fishing vessels.

Photo credit: Umeed Mistry (2), SADSTIA (3)

Bottom trawling is without a doubt one of the most devastating human activity in the ocean. Studies show that these nets can suck up to 41% of all invertebrate life from the sea floor and cause grave damage to cold water coral reefs and seagrass beds. Trawling releases carbon from marine sediments. Fishing boats that trawl the ocean floor release as much carbon dioxide as the entire aviation industry. Bottom trawls are some of the worst fishing gear when it comes to bycatch. Studies suggest that about 46 % of all bycatch comes from bottom trawls.

Purse seining

Purse seines are used in the open ocean to target dense schools of fish. Then, the ends of the net are synched together like a bag and pulled aboard with the fish inside.

Purse seines have no contact with seabed and can have low levels of bycatch, but purse seines may catch vulnerable species. Targeting tuna has been particularly associated with bycatch of mammals and sharks.

To conclude, we can divide the risks of commercial fishing into two categories. The first one is connected with overfishing as a whole. Roughly 90 % of the world’s fish stocks are now fully fished or overfished according to the most recent report by the UN’s Food and Agriculture Organization (FAO). The second are the threats of the methods themselves, including destroying vital parts of the ocean's environment and huge rates of bycatch.

But millions of people and communities depend on fishing as a main source of protein and also livelihood. Our goal is to provide information, clarify the situation, offer alternatives and explain the concept of a sustainable consumption of seafood. Stay tuned for our next article about sustainable fishing methods and sustainable seafood.

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