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Too many nutrients in water are bad for fish farming– here’s how ASC aims to fix that

April 21, 2023

Monitoring water quality is a crucial topic in fish farming and that’s because the ecological balance of the world’s water resources is extremely delicate.

Too much of something could potentially tip the scale and could result in adverse effects in aquaculture. Addressing the risk of eutrophication is one of them. This happens where there are too many nutrients (such as nitrogen or phosphorous) in the water which could lead to harmful algal bloom, reduction of dissolved oxygen and even fish kills events.

The new Water Quality proposal, which is aimed to be included in the Aquaculture Stewardship Council (ASC) Farm Standard, categorises receiving waters according to their nutrient retention capacity based on two major water systems: lentic systems (water bodies with still or slow flow such as lakes or reservoirs) or lotic systems (water bodies with faster flow such as rivers).

We spoke to ASC’s Head of Standards Javier Unibazo about how the new Water Quality proposal can prevent eutrophication, and ultimately, save our water resources and contribute to effective farm management.

Q: Why is Water Quality an important topic when talking about fish farming?

A: The monitoring of water quality in fish farming is a crucial topic if we want to address the risk of eutrophication. The effect of eutrophication can kill sensitive fish species and cause loss of biodiversity at local and regional scales. The general deterioration of water quality may also preclude water use by other communities and industries. 

Q: Can fish farms contribute to eutrophication?

A: Possibly. The release of nutrients, nitrogen (N), phosphorus (P), and suspended particles from feed and fertiliser used in fish farming can contribute to eutrophication. These contributions can be limited if a farm adopts the right measures.

Q: What changes are we now applying to the ASC Water Quality requirements and why?

A: The current standards contain requirements linked to an individual farm site, which might have limited or insignificant effects on a water body. The new water quality proposal deviates from that approach and moves to an approach based on risk in which the cumulative effect of multiple users is considered.  This new approach acknowledges that imposing requirements at a farm level, irrespective of the water body’s carrying capacity, is not enough to protect biodiversity and ecosystem function. Considering the cumulative nature of eutrophication, the new water quality proposal categorises receiving waters according to their nutrient retention capacity, differentiating between still or slower-flowing systems, also called lentic systems, and faster-flowing systems, known as lotic systems.

In this context, the indicators within the proposal have been developed to identify the nutrient retention capacity of the receiving water body and the susceptibility of at-risk water bodies to additional nutrient inputs. Where relevant, additional assimilative capacity assessment and coordinated area management agreements and actions are required to reduce the rate of change in the trophic status and prevent the eutrophication of a water body.

Q: What happens if the activities of multiple farms (that can be ASC as well as non-ASC certified) are actually causing eutrophication?

A: The proposal requires ASC certified farms to monitor water quality to prevent eutrophication by identifying when a water body is starting to show signs of trophic status changes. For lentic systems, when this is identified, the proposal requires ALL farms located in that at-risk water body to participate in an Area Management Agreement (AMA) to collectively monitor, prevent and mitigate eutrophication impacts. If farms do not participate or do not reach an agreement, farms located in that water body will not be in compliance with the proposed requirement.

Q: Would that mean that ASC certified farms would lose certification?

A: So, once the risk of eutrophication is identified, all farms operating in that water body would be inclined to collaborate and solve the issue, as the consequences would have negative effects not only on the environment but on their businesses too. If this still results in farm non-conformities with the ASC criterion, the farm could potentially loose certification, as it would happen with any other case of non-compliance with the ASC standards. We envision a world where aquaculture plays a major role in supplying food and social benefits for humanity whilst minimising negative impacts on the environment. And adopting these new measures on water quality will help us achieve that. We would, of course, hope that no farm shall lose certification because of other “irresponsible” farms, but our aim is to drive for improved practices ensuring that no harm is made to the environment.

Q: What do the proposed changes mean for a farmer?

A: The proposal seeks to simultaneously look at impacts as well as require preventative measures. Consequently, farms will be able to understand their context better in relation to the water body they are located in and to identify when the risk of eutrophication is increasing. If an increased risk is identified, the proposal provides farms with the means to address that risk by requiring collective actions of all the farms located in the water body, which will incentivise collaboration to ensure good management of water quality. Also, by incorporating reporting requirements in the proposal, certified farms are contributing to improving the understanding of water quality impacts in water bodies which can only lead to improved practices.

Exciting developments are underway for the ASC Farm Standard which includes the new requirements on Water Quality. There will be a final 30-day consultation on the final draft of the ASC Farm Standard in September 2023.

The ASC Farm Standard will be released in the second quarter of 2024 and will be effective a year after the release.

For more information, please visit the Alignment: ASC Farm Standard page.

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