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Fishing Techniques & Their Effects on Ecosystems

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  • 0:00 Fisheries of the World
  • 0:46 Destructive Techniques
  • 3:26 Ecological Impacts
  • 4:54 Conservation Efforts
  • 6:27 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Certain fishing techniques are used because they are very efficient. However, many of these techniques are also very destructive to ecosystems and the physical environment. In this lesson, you'll learn about some of these techniques and how they affect the ecosystems they are used in.

Fisheries of the World

Have you ever had a delicious tuna salad sandwich? Or perhaps you cracked open a tasty lobster tail and dipped it into warm, melted butter. What about a nice, refreshing shrimp cocktail shared with friends on a summer afternoon? Each of these constitutes a fishery, which is simply the act of catching a certain species or group of species of fish or shellfish.

Fisheries are important worldwide because they provide an important protein source for many people. Unfortunately, though, many of the world's fisheries are in decline due to things like habitat loss, overharvesting, pollution, and the ever-increasing human population. In fact, it's estimated that at least 80% of the world's monitored fisheries are either fully or overexploited, meaning that the fishery is being fished above a sustainable level.

Destructive Fishing Techniques

Fisheries of the world are in trouble because we are fishing too much, but also because of different types of gear used. Unfortunately, many modern fishing techniques are destructive in one way or another. Some techniques are physically harmful to the environment, while others catch large amounts of bycatch, which is marine life that is unintentionally caught in the fishing gear.

One very popular, but very destructive fishing technique is bottom trawling. This is when a fishing net is pulled along the seafloor behind a boat. Imagine a giant bulldozer plowing through your neighborhood, and you'll get the idea here - the people, houses, cars, lawns, and everything else get scooped up as the dozer goes along indiscriminately. A trawl net is also very efficient at catching everything in its path, including marine life and seafloor structure. In fact, it can remove up to 25% of the local seabed life in just one pull!

Another potentially harmful fishing technique is longline fishing. This technique uses a long line with baited hooks or traps that sit in the water. This technique is often used for catching things like swordfish or crabs and gets its name because some longlines extend for up to 50 miles with thousands of hooks! Because of this, longlines have a high rate of bycatch, especially animals like sea turtles and birds.

Like longlines, gillnets are also well-known for creating large amounts of bycatch. Gillnets are like walls of netting because they are vertically oriented panels of netting that catch fish by their gills as they pass through. Gillnets can also be quite long (several miles) and may even extend hundreds of feet down into the water. Unfortunately, gillnets don't just catch fish - they can potentially catch anything that might happen to try and swim through them.

Dynamite fishing is just what it sounds like - the use of explosives to blast fish from the water. The shock of the explosion sends the fish up to the surface where they can be collected by fishermen, and while illegal in many places, this is a popular fishing method because it is cheap and easy. It's also very dangerous, though. Not only does dynamite fishing pose a great risk to the fisherman using the explosives (who may lose an arm, a leg, or worse), but it also destroys the physical environment and kills anything else that happens to be in the water where the explosion occurred.

Ecological Impacts

Just like anything else in nature, the organisms that make up a fishery are important components of both local and global ecosystems. Many of the fishing techniques just mentioned have lasting effects on the physical environment as they plow or explode through the ground. But in addition to the physical destruction that may occur from fishing, there are also lasting ecological effects.

Each species is part of an intricate ocean food web, and if one component is reduced from too much fishing, it can disrupt the entire balance of that web. For example, if prey species, like sardines and anchovies, are removed in large amounts, this disrupts the natural supply of food for larger predators. Likewise, removing a top predator, like sharks or tuna, means that the prey populations they usually keep in check can now thrive and expand to unnatural levels.

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