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Bycatch is most commonly understood as marine species that are caught unintentionally while fishing for other species. Some fish caught unintentionally might be valuable so they are retained, while others are returned to the ocean.

What is bycatch?

There are no widely accepted definitions for 'bycatch' or the commonly used term 'discards'. To avoid confusion and ensure consistent auditing of fisheries, the MSC uses the term 'unwanted catch' in its Standards documentation.

Unwanted catch includes undersized or surplus fish that fisheries do not have a quota for, as well as endangered, threatened, and protected (ETP) species, and other unwanted marine species.

Why is unwanted catch a problem?

Unwanted catch can lead to overfishing and negatively impact populations and ecosystems.

If fish or other species are regularly caught but a fishery does not have effective management plans in place, the stock may not be at a healthy level and overfishing could quickly occur.

This poor management could also disrupt the food chain by inadvertently taking fish that other species rely on as food. Unmanaged unwanted catch can reduce the population of a fish species to a point where it is difficult to replenish.

Where unwanted catch is not properly managed or mitigated, it can lead to devastating effects on habitats and marine life such as turtles and marine mammals. The UN Food and Agriculture Organization estimates that annually 9.1 million tonnes (10% of annual catches) are discarded, and at least 20 million individuals ETP species interact with fisheries.

These types of fishery impacts could mean populations of endangered species are unable to recover to healthy numbers. In Mexico, the vaquita, a type of porpoise, is commonly entangled in gillnets and is facing imminent extinction.

Unwanted catch is a global challenge that requires the support of industry, scientists, and NGOs, working together towards improvements in fisheries management. Responsible, well-managed fisheries will proactively reduce their unwanted catch.

Can fishing with unwanted catch be sustainable?

As long as the amount of unwanted catch is well-managed and affected fish populations remain healthy, fishing activity can be deemed sustainable.

Most sustainable fishing will include some level of unwanted catch, but effects can be minimized to prevent long-term impact on the wider ecosystem.

The MSC program helps fisheries manage their unwanted catch levels by providing a benchmark that includes the latest science and best practice in fisheries management. Fisheries use the MSC Fisheries Standard as a framework to make improvements and demonstrate that interactions with these species are minimized.

All MSC certified fisheries must actively reduce mortalities of unwanted catch. Where species are endangered, threatened, or protected, fisheries must ensure activity is not hindering their population recovery.

What is an acceptable level of unwanted catch?

The acceptable level of unwanted catch varies depending on the species and where it is being caught. Even if the level of unwanted catch is low, it could be that the species is endangered, so even a small amount of unwanted catch could be deemed too much.

By contrast, other species that are not currently vulnerable to extinction may be more resilient to fishing pressure. Ultimately, fishing is deemed sustainable when it can continue year after year, without long term impacts on the population or the marine ecosystems on which the fish depend.

How can unwanted catch be reduced?

Unwanted catch can be reduced through certification to the MSC Fisheries Standard. Fishing activity is often improved during and after certification.

Fisheries can reduce their impact by contributing to research, implementing fishing method modifications, or measures to build up populations. Fisheries significantly improve as they stay in the program, thereby lessoning their impact on the wider ecosystem.

The MSC is not prescriptive about what devices or methods MSC certified fisheries use to minimize unwanted catch. There is much innovation in the sector that we are helping to drive through our Ocean Stewardship Fund.

Accurate data is essential to understand if management strategies are effective at mitigating impacts. In the North Sea, a project is improving a fishery’s reporting of interactions with endangered, threatened and protected species through the development of a mobile app.

In South Africa, bespoke bird-scaring lines are being developed in the certified inshore hake trawl fleet. Long ropes with colored streamers hang off the back of the boat to deter the seabirds. The fishery has had great success reducing unwanted catch of seabirds by 95%.

If fisheries 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 MSC blue fish ecolabel.

Improvements to our Fisheries Standard

In October 2022 we published a new version of the MSC Fisheries Standard, following the most comprehensive review to date

The new version includes revised requirements to help reduce impacts on ETP species, and species that cannot be targeted by MSC certified fisheries (marine mammals, birds, reptiles, and amphibians). The new requirements will increase confidence that only fisheries that can prove they are not impacting populations or harming recovery can achieve MSC certification.  

Our new Standard will also ensure the impacts of ghost gear are explicitly considered during every fisheries assessment, with fisheries required to have effective measures in place to minimize gear loss and mitigate the impact of any lost gear. These requirements now apply to fish aggregating devices (FADs): any lost FADs must be accounted for, and fisheries must demonstrate how they are avoiding and managing losses.