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Bycatch is fish or other marine species caught unintentionally while trying to catch another type of fish. In some cases, bycatch cannot be avoided, and unwanted fish end up in the fishing net.

Why is bycatch a problem?

Problems associated with bycatch include:

  • endangered, threatened and protected species such as turtles and dolphins are accidentally caught, injured or killed.
  • the food chain is disrupted by inadvertently taking fish that other fish rely on as food
  • the population of a fish species reduces to a point where it is difficult to replenish as the fishing gear may not be designed to allow juvenile fish to swim free and breed. 

Responsible, well-managed fisheries will proactively reduce their bycatch.

Is 40% of catch bycatch?

A paper from 2009 proposed a broader definition of bycatch to include all catch from "un-managed" fisheries. Under this definition, it was estimated that 40% of catch is bycatch. However, this definition has not been widely adopted. Research by Dirk Zeller, et al point to a figure of around 10% instead. Meanwhile, a UN FAO report (2018) cites a figure of 9.4%.

Find out more about this myth-buster from academics at the University of Washington in this blog.

How can fishing with unwanted catch be sustainable?

Fishing activity with bycatch can be deemed sustainable so long as the amounts of bycatch are well managed and the affected fish populations remain healthy.

Certain fishing methods can increase the likelihood of bycatch, but effective management is key to reducing it. One such method is Fish Aggregating Devices in tuna fishing.

When fishing activity is assessed to the MSC Fisheries Standard, scientists examine the amount and species of bycatch to see if it is environmentally sustainable.

The MSC uses the term 'unwanted catch' in the MSC Fisheries Standard to ensure consistent auditing of fisheries. Under this definition, 'unwanted catch' includes undersized or surplus fish that fisheries do not have a quota for, as well as endangered, threatened and protected species, and other unwanted marine species.

During an assessment, the fishing managers must demonstrate that they are not threatening fish populations and that they are implementing measures to minimise unwanted catch.

Bycatch explained in 1 minute

Bycatch explained in 1 minute

What is an acceptable level of by-catch?

The acceptable level of bycatch varies depending on where in the ocean it is being caught and on the species. For example, even if the level of bycatch is low, it could be that the species is endangered, and therefore that the level of bycatch is deemed too high. Some fish can also be returned alive to the sea in an effort to manage bycatch.

Bycatch in a fishing net

How can unwanted catch be reduced?

Bycatch can be reduced through certification to the MSC Fisheries Standard. Fishing activity is often improved during and after certification. Improvements can include contributions to research, modifications to fishing methods or measures to build up fish populations.

If fishing managers do not comply with their certification requirements and/or no longer meet the MSC Fisheries Standard, their certificate is suspended and seafood from that source can no longer be labelled and sold with the blue fish tick

Read about how smarter fishing practices dramatically reduced the number of seabird deaths in the Southern Ocean.

Read about how the Australian Northern Prawn Fishery industry has reduced bycatch with their innovative 'Tom's Fisheye' device.

Read about how 'banana pinger' audio device trials are reducing porpoise bycatch

Can I buy seafood free from bycatch?

Unfortunately, most fishing will include some bycatch because different marine creatures swim together.

But sustainable fishing can reduce bycatch to ensure fish populations are healthy and ecosystems are protected.

While fishing with zero bycatch may not be possible, MSC certified sustainable fisheries work to reduce their bycatch toward zero.

To be sure you’re purchasing sustainable seafood where bycatch is minimised, look for the MSC blue fish tick label.

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Our approach

Our approach

Our approach means everyone can play a part in that future while enjoying seafood, not avoiding it.

Our collective impact

Our collective impact

For more than 20 years fisheries, scientists, consumers and industry have been part of a collective effort to make sure our oceans are fished sustainably.

What is sustainable fishing?

What is sustainable fishing?

Sustainable fishing means leaving enough fish in the ocean, respecting habitats and ensuring people who depend on fishing can maintain their livelihoods.

Teach and learn about sustainable fishing

Teach and learn about sustainable fishing

Use our curriculum-relevant teaching and learning resources to discover how we can help keep our oceans healthy for generations to come.