Aquaculture Thematic Methods

1. Outcome

This Circular provides operational methods for accounting aquaculture operations within ocean accounting frameworks. Upon implementation, practitioners will be able to:

• Classify aquaculture systems according to their operational characteristics, species composition, and environmental setting, using ISIC and ISSCFC frameworks adapted for ocean accounting^[1]
• Compile site-level asset accounts tracking cultivated biological resources, production cycles, and stock changes, consistent with the asset accounting framework in TG-3.1 Asset Accounts^[2]
• Quantify environmental interactions including nutrient loading, habitat modification, and genetic impacts on wild populations, complementing the residual flow methods in TG-3.4 Flows from Economy to Environment^[3]
• Account for feed and resource dependencies linking aquaculture production to wild fish stocks and terrestrial inputs, extending the aquatic resource accounting established in TG-3.9 Aquaculture Accounts^[4]
• Record disease-related losses and biosecurity costs as components of the aquaculture production account, with catastrophic losses treated consistently with SEEA AFF guidance^[5]
• Derive policy-relevant indicators for aquaculture carrying capacity assessment, feed conversion efficiency monitoring, and environmental footprint analysis, supporting decisions on sustainable aquaculture expansion^[6]

The methods enable integration of aquaculture data with broader ocean accounts, supporting policy analysis on sustainable aquaculture development, carrying capacity assessment, and cumulative impact evaluation. These accounting methods connect upward to economy-wide measurement through TG-2.5 Structure and Function of the Ocean Economy where aquaculture's contribution to gross value added and employment is measured, and to pollution accounting through TG-2.7 Pollution and Other Flows to Environment where nutrient discharges from aquaculture are aggregated with other sources. The broader food security context -- including aquaculture's contribution to protein supply and nutritional outcomes -- is addressed in TG-2.3 Social and Livelihood Dependencies on Ocean Ecosystems. Aquaculture's contribution to SDG 14 (Life Below Water) -- particularly target 14.7 on sustainable use of marine resources and target 14.2 on sustainable management of marine and coastal ecosystems -- can be assessed through the accounts compiled using this Circular. The fisheries stock assessment methods in TG-6.7 Fisheries Accounting: Integrating Stock Assessment provide complementary guidance for the wild-capture dimension of fish supply.^[7]

2. Requirements

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts -- for the conceptual framework of environmental-economic accounting principles, asset boundaries, and production concepts as applied to ocean contexts.

• TG-3.9 Aquaculture Accounts -- for the foundational methods for compiling physical asset accounts for aquatic resources, including the distinction between cultivated and non-cultivated biological resources, which this Circular extends with site-specific thematic methods.

2.1 Data Requirements

Implementation requires access to:

• Aquaculture production statistics: Harvest quantities by species, production system, and site location, typically available from national fisheries agencies and FAO global aquaculture databases^[8]
• Licence and site registration data: Information on permitted sites, lease areas, and production capacity limits, essential for carrying capacity analysis and spatial integration with ecosystem extent accounts^[9]
• Environmental monitoring data: Water quality parameters, nutrient concentrations, and benthic condition assessments, obtained from regulatory agencies, industry reporting, or dedicated surveys^[10]
• Feed and input records: Feed quantities, composition, and source materials, typically maintained by producers for production management but potentially requiring survey collection for statistical purposes^[11]
• Mortality and escape records: Stock losses from disease, escapes, and other causes, often required under regulatory frameworks though data quality varies across jurisdictions^[12]

2.2 Statistical Classifications

Aquaculture activities are classified according to:

• ISIC Division 03: Fishing and aquaculture, specifically Group 032 (Aquaculture) with classes 0321 (Marine aquaculture) and 0322 (Freshwater aquaculture)^[13]
• SEEA CF land use and water area categories: Land used for aquaculture (1.3), including hatcheries (1.3.1) and managed grow-out sites (1.3.2); plus water area categories for inland waters (2.1), coastal waters (3.1), and EEZ areas (4.1) used for aquaculture or holding facilities^[14]

Marine spatial use classifications for aquaculture sites should be consistent with those applied in TG-2.3 Social and Livelihood Dependencies on Ocean Ecosystems and the ecosystem extent accounting framework where applicable, ensuring that aquaculture lease areas are recorded in a manner compatible with broader marine spatial planning accounts.

3. Guidance Material

3.1 Aquaculture Systems Classification

Aquaculture encompasses diverse production systems that differ fundamentally in their environmental interactions, resource requirements, and accounting treatment. The FAO defines aquaculture as:

"The farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also implies individual or corporate ownership of the stock being cultivated."^[15]

This definition, adopted in SEEA CF para. 5.409 and applied in TG-3.9 Aquaculture Accounts, establishes the production boundary for aquaculture. For statistical purposes, aquatic organisms harvested by an individual or corporate body that has owned them throughout their rearing period contribute to aquaculture, while organisms exploitable by the public as common property resources constitute capture fisheries harvest.^[16]

3.1.1 Marine Cage Systems

Marine cage aquaculture involves net-pen structures moored in coastal or offshore waters, typically used for finfish species such as salmon, sea bass, and cobia. Key accounting characteristics include:

• Site boundaries: Defined by lease area coordinates rather than land area; recorded under SEEA CF category 3.1 (coastal waters used for aquaculture) or 4.1 (EEZ areas used for aquaculture)^[17]
• Asset classification: Farmed fish are produced assets, either inventories (for grow-out stock) or fixed assets (for breeding stock), as specified in SEEA CF para. 5.441^[18]
• Environmental exposure: Open exchange with surrounding waters means nutrient and disease interactions extend beyond site boundaries, requiring coordination with the environmental flow accounting methods in TG-3.4 Flows from Economy to Environment^[19]

3.1.2 Coastal Pond Systems

Pond-based aquaculture utilizes constructed enclosures on land or in intertidal areas, commonly used for shrimp, tilapia, and milkfish. Accounting features include:

• Land area recording: Pond area classified under SEEA CF category 1.3.2 (managed grow-out sites on land), enabling integration with terrestrial land use accounts^[20]
• Water management: Controlled water exchange enables nutrient budgeting and effluent treatment accounting, with mass balance calculations possible at the site level^[21]
• Production intensity: Semi-intensive to intensive systems require accounting for feed inputs and aeration costs, with intensity classification affecting environmental loading rates and resource requirements per unit production^[22]

3.1.3 Integrated Multi-Trophic Aquaculture

Integrated multi-trophic aquaculture (IMTA) co-cultures species at different trophic levels, where waste from fed species (e.g., finfish) provides nutrients for extractive species (e.g., seaweed, shellfish). These systems present specific accounting considerations:

• Nutrient cycling: Internal recycling reduces net environmental loading; accounts should distinguish gross and net nutrient flows, as integrated systems may achieve negative net nutrient loading when extractive species uptake exceeds fed species contributions^[23]
• Multiple outputs: Production accounts record outputs from each component species with appropriate allocation of shared inputs, following standard SNA treatment of joint production^[24]

3.1.4 Species Coverage

Ocean-relevant aquaculture species groups follow the ISSCFC classification adapted for the SEEA AFF, including:

Table 3.1: Aquaculture species groups and key accounting considerations

3.2 Site-Level Accounting

3.2.1 Carrying Capacity Assessment

Carrying capacity represents the maximum production intensity that can be sustained without unacceptable environmental degradation. For aquaculture sites, carrying capacity assessment considers four dimensions:^[25]

• Physical carrying capacity: Maximum stocking density based on water exchange, oxygen availability, and waste assimilation
• Production carrying capacity: Maximum yield achievable given infrastructure and resource constraints
• Ecological carrying capacity: Maximum production compatible with maintenance of ecosystem condition indicators
• Social carrying capacity: Maximum production acceptable to other users and stakeholders

The asset account for aquaculture sites should record carrying capacity estimates as context for interpreting stock and production data. Changes in estimated carrying capacity over time may reflect environmental degradation, improved management practices, or updated assessment methods. These concepts parallel those applied for livestock carrying capacity in the SEEA AFF (para. 3.90) and tourism carrying capacity in the SF-MST. The ecological dimension of carrying capacity connects to the condition accounting methods in TG-2.3 Social and Livelihood Dependencies on Ocean Ecosystems, while the residual flow dimension should be recorded consistently with TG-3.4 Flows from Economy to Environment.

3.2.2 Production Cycle Accounting

Aquaculture production cycles vary by species and system, from several months (shrimp) to multiple years (salmon). The physical flow account for aquaculture should record:^[26]

Table 3.2: Aquaculture physical flow account structure

The nominal harvest represents output for purposes of physical flow accounts, measured in live weight equivalent consistent with FAO aquaculture production statistics.^[27]

3.2.3 Mortality and Catastrophic Loss Recording

Stock mortality in aquaculture includes both routine losses (normal mortality) and exceptional events requiring separate recording:^[28]

• Normal mortality: Predictable losses based on species and system characteristics; recorded as reductions in stock
• Disease outbreaks: Unexpected losses from pathogen events; recorded as catastrophic losses if exceeding normal thresholds (e.g., mortality exceeding two standard deviations above the historical average for the species and system type)
• Environmental events: Losses from storms, harmful algal blooms, or temperature extremes; recorded as catastrophic losses
• Predation: Losses to predators (seals, birds); recorded under normal mortality or other reductions

The SEEA AFF notes that "unexpected large losses from disease or natural disasters should be recorded as catastrophic losses" (para. 3.185), providing the threshold principle for distinguishing normal from exceptional mortality events.^[29]

3.2.4 Escape Recording

Escapes from aquaculture facilities represent a distinctive accounting challenge, requiring reclassification from cultivated to natural stocks. The SEEA AFF acknowledges this complexity:

"Challenges may arise when recording reclassifications of cultivated and natural fish stocks, for example when wild fish are introduced as breeding stock or when cultured seeds are released into the wild; escapes by fish from aquaculture facilities in river and marine environments can also occur."^[30]

Escapes should be recorded as reductions in cultivated stock with corresponding entries in wild population accounts where these are maintained. For consistency with the wild stock accounting methods established in TG-3.9 Aquaculture Accounts, escape events should include the species, estimated number and biomass of escaped individuals, and whether the species is native to the receiving environment. This information supports both the asset balance for cultivated stocks and the qualitative assessment of genetic interaction risks discussed in Section 3.3.3.

3.3 Environmental Interactions

The environmental interactions of aquaculture span multiple flow categories and connect to several other accounting domains. The following matrix summarizes the principal interactions and their accounting treatment.

Table 3.3: Aquaculture environmental interaction matrix

3.3.1 Nutrient Loading

Fed aquaculture systems release nutrients to the environment through uneaten feed, faeces, and metabolic excretion. Nutrient loading accounts should record:^[31]

Table 3.4: Nutrient mass balance components for aquaculture

The SEEA AFF provides guidance on nutrient budgets stating: "The basis for measuring nutrient budgets is tracking the nitrogen and phosphorous cycles... Through consistent measurement of each part of those cycles, an overall indication of change can be obtained along with measures of surpluses or deficits of nitrogen and phosphorus" (para. 4.79).^[32]

For integration of nutrient loading with environmental flow accounts, the residual flow recording methods in TG-3.4 Flows from Economy to Environment provide the standard framework. Aquaculture nutrient discharges should be recorded as emissions to water, with the mass balance approach described above providing the quantification method specific to aquaculture sites.

3.3.2 Habitat Modification

Aquaculture development can modify marine and coastal habitats through multiple pathways:

• Direct conversion: Mangrove clearing for pond construction; seabed modification for on-bottom culture
• Shading effects: Light reduction beneath cage and raft structures affecting benthic communities
• Organic enrichment: Sediment accumulation beneath cage sites altering benthic fauna composition
• Structural provision: Cage structures and shellfish lines providing habitat for associated species

Habitat modification should be recorded in conjunction with land use and ecosystem extent accounts, noting conversions between ecosystem types and changes in ecosystem condition. Where ecosystem extent accounts are compiled, the conversion of natural habitats (e.g., mangrove forest, seagrass beds) to aquaculture use should be recorded as land use change, consistent with SEEA EA extent accounting principles. The condition of receiving environments -- particularly benthic condition beneath cage sites -- provides an indicator for the ecological carrying capacity dimension discussed in Section 3.2.1.^[33]

3.3.3 Genetic Impacts

Escaped farmed fish may interbreed with wild populations, potentially affecting genetic diversity and local adaptation. While quantitative genetic accounting methods remain under development, the following information supports qualitative assessment of genetic interaction risks:

• Escape volumes: Numbers and biomass of escaped stock by species, as recorded in the escape account (Section 3.2.4)
• Species overlap: Whether farmed species are native or non-native to the receiving region, with non-native species posing additional ecological risks beyond genetic introgression
• Breeding potential: Whether escapes are reproductively mature or sterile (e.g., triploid stock), affecting the likelihood of interbreeding with wild populations

As genetic monitoring and molecular methods advance, quantitative indicators may become feasible for inclusion in condition accounts. Compilers should monitor developments in this area and consider incorporating genetic diversity indicators where local monitoring programmes provide suitable data.

3.4 Feed and Resource Use

3.4.1 Fishmeal and Fish Oil Dependency

Marine ingredients in aquafeed create linkages between aquaculture production and wild fish stocks. The SEEA AFF notes that:

"Fish products... in granule or pellet form... provide nutrition in a stable and concentrated form, which enables the fish to feed efficiently and grow to their full potential. Many of the intensively farmed fish are carnivorous, including, among others, Atlantic salmon, trout, sea bass and turbot. In line with the emergence of modern aquaculture in the 1970s, fish meal and fish oil have become major components of feed for those species."^[34]

Accounts should record feed composition and sourcing to enable assessment of the net contribution of aquaculture to fish supply:

Table 3.5: Feed component recording for aquaculture accounts

Feed ingredient sourcing should be linked to wild fish stock accounts compiled under TG-3.9 Aquaculture Accounts and the fisheries accounting framework in TG-6.7 Fisheries Accounting: Integrating Stock Assessment to enable assessment of net contribution to fish supply.^[35]

3.4.2 Fish-In Fish-Out Ratios

The Fish-In Fish-Out (FIFO) ratio measures the quantity of wild fish required (as feed ingredients) to produce one unit of farmed fish. This indicator links aquaculture production to wild fish stock accounts:

$$\text{FIFO} = \frac{\text{Wild fish in feed (tonnes)}}{\text{Farmed fish output (tonnes)}}$$

FIFO ratios vary substantially by species and system:

• Salmon and marine carnivores: FIFO typically 1.5--3.0
• Tilapia and herbivorous species: FIFO typically 0.3--0.8
• Filter-feeding shellfish: FIFO = 0 (no feed inputs)

Declining FIFO ratios over time reflect increasing substitution of marine ingredients with terrestrial alternatives and improved feed conversion efficiency. For sustainability assessment purposes, FIFO trends should be interpreted alongside total production volume -- a declining ratio accompanied by expanding production may still result in increased absolute demand for wild fish in feed. Compilers should present both the ratio and the absolute quantities of wild fish used in feed to enable comprehensive policy analysis.^[36]

3.4.3 Feed Sources and Sustainability

Feed source tracking enables assessment of sustainability implications across three principal categories:

• Reduction fisheries: Wild fish harvested specifically for fishmeal and fish oil production; these volumes should be linked to wild stock accounts and deducted from the net fish supply contribution of aquaculture
• Processing by-products: Trimmings from fish processing operations; represents resource efficiency improvement and should be distinguished from dedicated reduction fishery catch in feed composition records
• Terrestrial inputs: Soy, wheat, and other crop-derived ingredients; linked to agricultural accounts where available, with attention to land use change implications in source regions

3.5 Disease and Biosecurity

3.5.1 Disease-Related Losses

Disease represents a significant cause of aquaculture mortality and economic loss. The disease account should record:

Table 3.6: Disease loss classification for aquaculture accounts

Disease losses exceeding historical norms -- for example, mortality greater than two standard deviations above the species- and system-specific average -- should be classified as catastrophic losses for accounting purposes. This threshold is consistent with the SEEA AFF treatment of unexpected livestock and crop losses and provides a replicable criterion for compilers.

3.5.2 Treatment Chemical Use

Veterinary treatments and disease control chemicals should be recorded in physical flow accounts:

Table 3.7: Treatment chemical recording for aquaculture accounts

These flows contribute to understanding of environmental emissions from aquaculture and resource inputs to production. Treatment chemical emissions should be recorded consistent with the residual flow methodology in TG-3.4 Flows from Economy to Environment for emissions to water, ensuring that aquaculture chemical use is integrated with broader pollution accounting.

3.5.3 Biosecurity Investment

Biosecurity measures represent capital and operating expenditures aimed at preventing disease introduction and spread:

• Infrastructure: Nets, barriers, treatment systems (recorded as gross fixed capital formation where these represent durable investments)
• Monitoring: Surveillance, testing, and certification programmes (recorded as intermediate consumption)
• Management protocols: Fallowing, single year-class stocking, and area management agreements (costs recorded as intermediate consumption)

Biosecurity investments should be recorded in monetary accounts as intermediate consumption (operating costs) or gross fixed capital formation (infrastructure investments), supporting analysis of prevention versus treatment cost-effectiveness across production cycles.

3.6 Compilation Procedure

The compilation of aquaculture thematic accounts follows a systematic procedure that integrates site-level data with the broader ocean accounting framework. This procedure builds on the foundational methods in TG-3.9 Aquaculture Accounts and aligns with the supply and use table framework described in TG-2.5 Structure and Function of the Ocean Economy.

Step 1: Data assembly and validation

Assemble aquaculture production data from fisheries agencies, site registration records from licensing authorities, and environmental monitoring data from regulatory programmes. Validate internal consistency between production records and site capacity data. Where inconsistencies are identified, document data quality issues following TG-0.7 Quality Assurance and establish reconciliation procedures.

Step 2: Site-level asset account compilation

For each aquaculture site or site cluster, compile a physical asset account recording opening stock, natural growth, harvest, mortality, escapes, and closing stock (Table 3.2 format). Aggregate site-level accounts to species groups and production system types. Verify that the accounting identity holds: Closing stock = Opening stock + Natural growth - Harvest - Mortality - Escapes.

Step 3: Environmental flow recording

Apply nutrient mass balance calculations (Table 3.4) to estimate nitrogen and phosphorus discharges from fed aquaculture systems. Record these flows in the residual flow accounts following TG-3.4 Flows from Economy to Environment. For coastal pond systems with point-source discharges, record measured effluent volumes and nutrient concentrations where monitoring data are available.

Step 4: Feed dependency analysis

Compile feed use data by species and system type. Decompose feed into fishmeal, fish oil, vegetable protein, and other ingredients (Table 3.5). Calculate FIFO ratios for fed aquaculture systems. Link fishmeal and fish oil use to wild fish stock accounts compiled under TG-6.7 Fisheries Accounting to enable net fish supply analysis.

Step 5: Integration with economy-wide accounts

Extract aquaculture output, intermediate consumption, and value added from national supply and use tables, following the industry delineation in TG-2.5 Structure and Function of the Ocean Economy Section 3.7. Reconcile physical output quantities from the asset accounts with output recorded in monetary terms, applying appropriate unit value factors. Record gross fixed capital formation in aquaculture infrastructure and equipment.

Step 6: Indicator derivation

Calculate policy-relevant indicators from the compiled accounts:

• Production efficiency: Feed conversion ratio (FCR = feed used / harvest weight), enabling assessment of resource use efficiency
• Environmental intensity: Nutrient discharge per unit production (kg N per tonne harvest), supporting carrying capacity evaluation
• Economic performance: Gross value added per unit production, labour productivity, and capital intensity
• Carrying capacity utilisation: Actual production as percentage of estimated site carrying capacity

These indicators support the decision use cases described in Section 3.7.

3.7 Decision Use Cases

Aquaculture accounts compiled using the methods in this Circular support a range of policy and management decisions. Understanding these use cases helps compilers prioritise data collection and ensure that accounts address user needs.

3.7.1 Sustainable Aquaculture Expansion Planning

Decision context: Governments seek to expand aquaculture production to meet food security and economic development objectives while maintaining environmental sustainability. Decisions include site allocation, production licensing, and infrastructure investment.

Account inputs: Site-level asset accounts (Section 3.2), carrying capacity estimates (Section 3.2.1), nutrient loading data (Section 3.3.1), habitat modification records (Section 3.3.2).

Analytical outputs: Production potential by coastal zone, environmental loading relative to assimilative capacity, cumulative impact assessment across multiple sites, spatial optimisation of site allocation.

Connection to other circulars: Carrying capacity analysis links to ecosystem condition assessment in TG-2.3 Social and Livelihood Dependencies. GVA and employment projections link to economy structure analysis in TG-2.5 Structure and Function of the Ocean Economy.

3.7.2 Environmental Footprint Monitoring

Decision context: Regulatory agencies monitor aquaculture environmental impacts and enforce environmental standards. Decisions include permit renewals, enforcement actions, and adaptive management adjustments.

Account inputs: Nutrient mass balance (Table 3.4), treatment chemical use (Table 3.7), escape records (Section 3.2.4), benthic condition indicators (Section 3.3.2).

Analytical outputs: Trends in nutrient loading intensity, chemical use per unit production, escape frequency, and benthic impact indices. Comparison against water quality standards and regulatory limits.

Connection to other circulars: Nutrient discharges aggregate into pollution accounts in TG-2.7 Pollution and Other Flows to Environment. Habitat impacts connect to ecosystem degradation analysis in TG-2.8 Ecosystem Degradation.

3.7.3 Feed Conversion Efficiency Tracking

Decision context: Industry and government seek to improve resource efficiency and reduce dependency on wild fish stocks. Decisions include research and development priorities, feed formulation standards, and sustainability certification.

Account inputs: Feed composition (Table 3.5), FIFO ratios (Section 3.4.2), feed conversion ratios, wild fish stock status from TG-6.7.

Analytical outputs: Trends in FIFO ratios over time, share of feed from processing by-products versus reduction fisheries, comparison of actual versus best-practice FCR, net contribution to fish supply.

Connection to other circulars: Wild fish use in feed links to fisheries accounts in TG-6.7 Fisheries Accounting. Protein supply contributions link to food security analysis in TG-2.3 Social and Livelihood Dependencies.

4. Worked Example

This worked example illustrates the compilation of a site-level aquaculture account for a hypothetical marine cage salmon farm operating in coastal waters. The example demonstrates the physical asset account, production flow recording, nutrient loading calculation, and feed use accounting described in Section 3.

4.1 Site Description

The example site comprises a marine cage salmon farm with 12 net-pen cages located in a coastal embayment. The farm operates on a 24-month production cycle, stocking smolts in Year 1 and harvesting market-size fish in Year 2. The site is classified under ISIC 0321 (Marine aquaculture) and occupies a lease area recorded under SEEA CF water area category 3.1 (coastal waters used for aquaculture).

4.2 Physical Asset Account

The following physical asset account records stock changes over a single accounting period (one calendar year, mid-cycle):

Table 4.1: Physical asset account -- marine cage salmon farm (Year 2 of production cycle)

Accounting identity verification: 2,400 + 1,800 - 3,600 - 180 - 20 = 400. The account balances.

4.3 Nutrient Loading Estimate

Using a mass balance approach for nitrogen:

• Feed input: 4,320 tonnes of feed at 6.5% N content = 281 tonnes N
• Harvested biomass: 3,600 tonnes at 2.8% N content = 101 tonnes N
• Mortality and escapes: 200 tonnes at 2.8% N = 6 tonnes N (removed from system)
• Net N discharge to environment: 281 - 101 - 6 = 174 tonnes N

This net nitrogen discharge of 174 tonnes would be recorded as a residual flow to the marine environment under TG-3.4 Flows from Economy to Environment.

Loading intensity: 174 tonnes N / 3,600 tonnes harvest = 48 kg N per tonne production. This intensity metric can be compared against regulatory benchmarks or industry best practice to assess environmental performance.

4.4 Feed Use and FIFO Calculation

Feed composition and FIFO ratio for the production cycle:

Table 4.2: Feed composition and FIFO calculation

Wild fish equivalent in feed: fishmeal requires approximately 4.5 kg of wild fish per kg of meal; fish oil requires approximately 8 kg of wild fish per kg of oil. Therefore:

• Wild fish for fishmeal: 648 x 4.5 = 2,916 tonnes
• Wild fish for fish oil: 432 x 8.0 = 3,456 tonnes
• Total wild fish in feed (higher of the two, to avoid double-counting): 3,456 tonnes
• FIFO ratio: 3,456 / 3,600 = 0.96

A FIFO ratio below 1.0 indicates that the farm produces more fish (by weight) than the wild fish consumed in its feed, representing a net positive contribution to fish supply in weight terms. However, this analysis does not account for differences in protein quality or nutritional value between wild fish used in feed and farmed salmon produced.

Feed conversion ratio (FCR): 4,320 tonnes feed / 3,600 tonnes harvest = 1.2. This FCR is within the typical range for salmon cage culture (1.1--1.3) and indicates efficient feed utilisation.

4.5 Integration with Supply-Use Framework

To integrate this site-level account with the ocean economy accounts in TG-2.5 Structure and Function of the Ocean Economy, the following entries would be recorded:

Table 4.3: Integration with ocean economy supply-use table (ISIC 0321 -- Marine aquaculture)

The GVA of USD 21.4 million from this site would contribute to the aquaculture row in the ocean economy accounts. The employment of 48 FTE positions contributes to the aquaculture employment total. These figures enable calculation of labour productivity (GVA per worker = USD 445,500) and capital intensity (GFCF as percentage of GVA = 7.0%).

5. Compilation Considerations

5.1 Data Quality and Availability

Implementation of aquaculture thematic methods faces common data challenges that vary by jurisdiction and data type. Compilers should assess data quality along the following dimensions:

• Production data: Generally available from industry reporting to regulatory agencies and from FAO aquaculture statistics; typically the most complete data category. Compilers should verify consistency between national statistical agency records and industry association reports.
• Feed data: Often commercially sensitive; may require survey-based collection or estimation using species-specific feed conversion ratios applied to production volumes. Where direct data are unavailable, compilers should document the estimation methodology and associated uncertainty.
• Environmental data: Variable availability depending on monitoring requirements in each jurisdiction. Some countries mandate environmental monitoring at aquaculture sites (e.g., benthic surveys, nutrient monitoring), while others rely on ambient water quality monitoring that may not capture site-specific impacts.
• Disease data: May be subject to confidentiality restrictions in jurisdictions with mandatory disease reporting. Aggregate statistics on mortality rates and treatment chemical use may be available even where case-level data are restricted.

Minimum data requirements for compiling a basic aquaculture thematic account are production quantities by species and system type, and site location data. Additional data categories enable progressively more comprehensive accounts as described in the phased implementation approach below.

5.2 Phased Implementation

For jurisdictions with limited data availability or statistical capacity, a phased approach is recommended:

1. Phase 1 -- Production and asset accounting: Compile physical quantities of production, stock, and harvest by species and system type, drawing on existing aquaculture production statistics. This phase requires only production data and site registration records.
2. Phase 2 -- Environmental interaction accounting: Add nutrient loading estimates using mass balance calculations, habitat modification recording, and escape quantification. This phase requires environmental monitoring data and feed use estimates.
3. Phase 3 -- Feed dependency and disease accounting: Incorporate detailed feed composition, FIFO calculations, disease loss recording, and treatment chemical use. This phase requires industry-level feed data and disease reporting records.
4. Phase 4 -- Full integration with ocean accounts: Link aquaculture thematic accounts with asset accounts (TG-3.1 Asset Accounts), environmental flow accounts (TG-3.4 Flows from Economy to Environment), and ecosystem condition accounts to enable comprehensive sustainability assessment.

6. Acknowledgements

This Circular has been approved for public circulation and comment by the GOAP Technical Experts Group in accordance with the Circular Publication Procedure.

Authors: GOAP Secretariat

Reviewers: To be assigned

Note: This Circular addresses the thematic methods layer for aquaculture, extending the foundational aquaculture accounting guidance in TG-3.9.

7. References

• FAO and UN. 2020. System of Environmental-Economic Accounting for Agriculture, Forestry and Fisheries (SEEA AFF). Rome.
• FAO. 2008. Glossary of Aquaculture. Rome.
• United Nations et al. 2014. System of Environmental-Economic Accounting 2012: Central Framework. New York.
• United Nations et al. 2021. System of Environmental-Economic Accounting -- Ecosystem Accounting. New York.
• Greaker, M. and L. Lindholt. 2021. The resource rent in Norwegian aquaculture 1984--2020. Statistics Norway Discussion Papers No. 962.
• Asamoah, E.K. et al. 2012. A Production Function Analysis of Pond Aquaculture in Southern Ghana. Aquaculture Economics & Management 16(3): 183--201.
• FAO. 2024. The State of World Fisheries and Aquaculture 2024. Rome.