Indicators 2.5.1–2.5.3

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Feed Dependent

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Indicators 2.5.1–2.5.3

by Contact on 8 October 2026

Requirement

Indicator applicability: cage culture and suspended marine mollusc systems The UoC shall2828An exemption applies to sites situated in areas classified as having a ‘hard bottom’. Evidence is required to support the classification ‘hard bottom’. determine benthic status, following the method outlined in Appendix 7 (7.2.1, 7.3.1, 7.4.1, 7.7).

Indicator applicability: cage culture and suspended marine mollusc systems The UoC shall demonstrate an ‘Acceptable’ benthic status,2929An exemption applies to cage sites situated in lakes and reservoirs, where determination of benthic status is required (Indicator 2.5.1) but demonstration that the status is ‘Acceptable’ is not required for the first three years of the ASC Farm Standard being effective. following the method outlined in Appendix 7 (7.2.2, 7.3.2, 7.4.2).

Indicator applicability: cage culture and suspended marine mollusc systems The UoC shall ensure that the person conducting sediment sampling and analysis (see Indicator 2.5.1) is independent and has the necessary competencies, experience and training. In cases where regulatory requirements are defined, the UoC shall ensure that the person conducting the sampling and analysis complies with these requirements.

How Do I Interpret This Requirement?

  • The method for benthic monitoring for cage culture and suspended marine mollusc systems is composed of:

    • Sediment sampling zones and sampling locations across transects.

    • Benthic quality categories and thresholds for defining those categories and the benthic status.

[Sampling approach]

  • The method uses a three-level sampling approach:

    • The number of transects and sampling locations, as well as the complexity of analysis, may increase based on Level 1 or Level 2 monitoring results:

      • [Level 1] requires sampling along one transect in the direction of the predominant current. The samples are to be analysed for redox potential and total free sulphide.

      • Direction of the predominant current is the compass direction in which the water flows the majority of the time.

        • [Level 2] requires sampling along three additional transects. The samples are to be analysed for redox potential and total free sulphide.

        • [Level 3] requires sampling as per Level 2 (at a minimum, on the two transects in the direction of the predominant current). The samples are to be analysed for three (of the 14) biotic indicators selected from Table 2 of Appendix 7 (7.1).

      • Sites should select biotic indicators that are more appropriate based on their location or based on regulatory requirements.

      • In Scotland, sites should select AZTI’s Marine Biotic Index (AMBI) as one of the biotic indicators since it is a component of the Infaunal Quality Index (IQI) required by the regulation in that country.

        • Sites can choose to commence monitoring at any of the three levels.

          • Previous benthic impact results can provide an indication of the level at which monitoring should commence.

        • The same sediment samples collected for Level 1 or Level 2 sampling can be used for the analysis required by Level 3 sampling.

          • Sites are not required to collect new sediment samples.

        • Transects:

          • In cases where a transect overlaps with another site, the direction of the overlapping transect should be adjusted.

            • The same applies to any transect/sampling station overlapping with land.

            • Transect directions should also be adjusted to avoid sampling in areas where water depth changes rapidly along the transect.

            • In all cases, each transect should be as close to 90 degrees from each other as possible.

            • In cases where multiple cages are located in close proximity, transects should be located at the edge of the last cage site.

          • Given the low complexity associated with Level 1 and Level 2 sampling and analysis, it is advisable for sites to conduct monitoring not only at the required timings by the indicator but also prior to those timings

      • The results can indicate the need for Level 3 sampling at the timings required by the indicator, thereby assisting in monitoring planning.

[Ecological Quality Status (EQS) categories]

  • Ecological Quality Status (EQS) categories are used to determine the benthic status (see more details on the categories in the

Evidence of Implementation

  • Production overview information:

    • Biomass (projected and current).

    • Feed delivered (projected and current).

    • Harvest (biomass, time of harvesting).

    • Bottom water temperature data.

    • Visual imagery confirming hard bottom.

  • Records:

  • Sampling activity, including:

    • Timing and person conducting sampling.

    • GPS sampling locations.

    • Competence, experience and training of the person conducting sampling and analysis.

    • Sampling analysis results.

Auditors Should Confirm

  • Sampling was conducted according to the method and timing stated in Appendix 7 (7.2, 7.3, 7.4), by cross-checking production overview information and records.

  • Competence, experience and training of the person conducting sampling.

  • Adequate level of personnel competence should be verified by observations and interviews.

  • The sampling analysis results that demonstrate an acceptable EQS.

Useful Resources

The benthic monitoring method for cage culture and suspended marine mollusc systems uses five Ecological Quality Status (EQS) categories to define abiotic and biotic qualities based on the seabed macrofaunal communities. The EQS categories are outlined in Table 1 below.

Table 1. Descriptions of benthic macrofauna assemblages for each of the five Ecological Quality Status (EQS) categories of the benthic monitoring method for cage culture and suspended marine mollusc systems:

EQS Category Description

High No or very minor disturbance: Species abundance, richness and diversity is high and sensitive taxa dominate. Opportunistic taxa are absent or of negligible abundance. Geochemical quality elements indicate aerobic conditions with low free sulphide toxicity.

Good Slight disturbance: The level of diversity and abundance of invertebrate taxa is slightly reduced. Most of the sensitive taxa are present but slightly reduced. Opportunistic taxa are present but negligible. Geochemical quality elements indicate aerobic sediment conditions with a slight increase in free sulphide levels.

Moderate Moderate disturbance: The level of diversity and abundance of invertebrate taxa is moderately reduced. Sensitive taxa have negligible abundance or are absent. Tolerant and first-order opportunistic taxa co-dominate in abundance. Geochemical quality elements indicate a moderate increase in anaerobic conditions with free sulphide levels known to be lethal to sensitive and indifferent taxa.

Poor Major disturbance: Evidence of major alterations to the values of the biological quality elements. Diversity is greatly reduced with sensitive and indifferent taxa showing negligible abundance or are absent. Tolerant taxa are sub-dominant to first-order opportunistic taxa. Geochemical quality elements indicate a major increase in anaerobic conditions and sulphide concentrations lethal to most taxa.

Bad Severe disturbance: Evidence of severe alterations to the values of the biological quality elements and in which large portions of the relevant biological communities normally associated with undisturbed conditions are absent. First-order opportunistic taxa dominate but are greatly reduced in abundance. Geochemical quality elements indicate a severe increase in sulphide concentrations that are lethal to all taxa.