Maintaining fish stocks

Sustainable fish stocks are at the heart of the MSC program. Ensuring that the world’s fish stocks remain healthy is vital for marine ecosystems and global food security.

According to the Food and Agriculture Organisation (FAO) 33% of global fish stocks are fished at unsustainable levels with another 60% already being fished at their maximum sustainable level.

MSC requirements for maintaining fish stocks

Principle 1 (sustainable fish stocks) of the MSC Fisheries Standard requires that fisheries do not overfish or deplete their target stock. For stocks that are already depleted but recovering, the fishery must not prevent the stock from recovering.

The Fisheries Standard requires that stocks are around the stock size that produces the maximum sustainable yield (MSY). Stock size is the amount (biomass) of fish that remain in the water. The maximum sustainable yield is the largest catch that fishers can take from a fish stock each year without affecting future years.

When assessing a fishery, certification bodies look at both the stock size and the harvest strategies that control fishing of that stock. A harvest strategy is the combination of monitoring, stock assessment, harvest control rules and management actions taken by a fishery. The harvest strategy needs to maintain stocks at a level that can support the maximum sustainable yield, or help it recover to this level if the stock has dropped below this.

Fish stocks are dynamic. Fluctuating environmental conditions and populations, combined with variation in fishing effort, mean that the size of fish populations, and the potential maximum sustainable yield, will change over time. This is especially true for small pelagic fish (fish that do not feed at the ocean bottom or near the shore) like herring or sprat, or short-lived invertebrates such as squid and octopus. To take variability and uncertainty into account, the MSC Fisheries Standard requires that harvest strategies are robust and precautionary.

Improving our Standards

Because protecting fish stocks is so central to the MSC program, there are a number of aspects being considered in our current Fisheries Standard Review.

We want to reduce the complexity and ambiguity of requirements on harvest strategies. This includes providing a clear definition of ‘responsive’ harvest strategies, as this term is used in the requirements but is currently not defined.

We are also simplifying part of the Standard so that certification bodies do not end up assessing the same harvest strategy in multiple components of Principle 1. We are also looking to see if we need to revise the requirements that allow stocks to be scored when they are rebuilding.

Fisheries that catch species with highly fluctuating populations often have to deal with rapid changes over time. This can cause problems in MSC assessments and lead to uncertainty about their status in the MSC program. We are currently considering how the MSC Fisheries Standard applies to these types of fisheries.

Some fisheries inevitably catch closely related species that look the same and are impossible to separate, such as the Southern Gulf of California Thread herring. These are referred to as inseparable or almost-inseparable species. We are making sure the Fisheries Standard is clear on how to assess the stocks of these inseparable species.

We also investigated if there are certified fisheries where the majority of catch is made up of fish that isn’t certified to carry the blue label. This could happen if the fishery catches a mixture of species but has chosen to only certify some of them. The catch may also contain bycatch (unwanted catch), though this must be limited in order not to harm the population levels of the bycatch species. 

Our research found that this happens very rarely (in less than 5% of fisheries analysed) and is nearly always resolved when fisheries are recertified. We have simplified the process for fisheries to have more of their catch assessed as a target stock (under Principle 1 of the MSC Fisheries Standard) rather than just measuring the environmental impact (under Principle 2). This means nearly every fishery certifies the majority of its catch at its next assessment, helping increasing the amount of certified sustainable seafood in the world.

We will continue to monitor the issue but this work is no longer part of our current Fisheries Standard Review. It is therefore not expected to result in any changes to the MSC Fisheries Standard in 2022.


What could change?

We do not plan to change how stocks are assessed against the Fisheries Standard, but we do plan to clarify the Fisheries Standard so that fish stocks are assessed consistently. Our intention on ensuring sustainable fish stocks, as set out in Principle 1, will not change as a result of the Fisheries Standard Review.

When would changes to the Standard happen?

If any part of the Standard is revised, a new version will be released in March 2022. The MSC Board of Trustees will make the final decision on implementation of any change, with the development process set out in the Fisheries Standard Review.

Get involved

To be notified when consultation opens, please register your interest in the Fisheries Standard Review. Information about future events, such as targeted consultations and workshops, will also be posted here.

For other questions on sustainable stock requirements please email us at

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