Aquaculture Accounts

1. Outcome

This Circular provides comprehensive guidance on compiling accounts for aquaculture within ocean accounting frameworks, addressing the fundamental distinction between cultivated biological resources (produced assets within the SNA production boundary) and natural biological resources (wild fisheries). Aquaculture represents a significant and growing component of global seafood production, with distinct accounting requirements that differ markedly from wild-capture fisheries^[1].

Aquaculture accounts serve critical decision use cases for governments managing blue food systems and coastal development. They inform sustainable aquaculture planning by quantifying production capacity, tracking environmental pressures from aquaculture operations (nutrient loading, habitat conversion), and revealing trade-offs between aquaculture expansion and ecosystem conservation. They support carrying capacity assessment by comparing actual production against environmental limits, enabling authorities to set appropriate licensing thresholds for coastal zones and marine areas. They enable GBF Target 10 reporting by tracking area under sustainable aquaculture management and documenting environmental impacts that must be minimized under the Kunming-Montreal Global Biodiversity Framework. They provide the evidence base for blue economy investment decisions, revealing whether aquaculture growth is economically productive while remaining within ecological boundaries. These functions connect directly to the policy frameworks described in TG-1.2 Blue Economy Policy and TG-1.5 OA and Fisheries Management, where aquaculture accounts provide quantitative evidence for balancing food security objectives with environmental sustainability.

The guidance covers production boundary treatment, asset classification for aquaculture stocks, carrying capacity and sustainable production considerations, and environmental interactions including feed inputs and waste outputs. By understanding aquaculture accounting methodology, readers will be equipped to compile accounts that capture both the economic contribution of aquaculture and its interactions with marine and coastal ecosystems. Section 3.2 provides a compilation procedure detailing the steps from data collection to account assembly. Section 3.6 presents worked examples with synthetic data for shrimp farm production accounts and mangrove conversion tracking, demonstrating how to populate accounts for common aquaculture scenarios. This Circular provides the accounting foundation for the thematic methodologies presented in TG-6.8 Aquaculture Thematic Methods.

2. Requirements

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts -- for the conceptual framework and key components of Ocean Accounts
• TG-0.2 Overview of Relevant Statistical Standards -- for the methodological foundations provided by SNA 2025, SEEA CF, and SEEA EA
• TG-3.1 Asset Accounts -- for the general methodology of physical and monetary asset accounts, including the treatment of natural aquatic resources (Section 3.3.1) and produced assets (Section 3.5)
• TG-3.3 Economic Activity Relevant to the Ocean -- for the industry classification framework within which aquaculture is recorded

Related Circulars:

• TG-1.5 OA and Fisheries Management -- for the broader fisheries management context and the relationship between aquaculture and wild-capture fisheries
• TG-3.2 Flows from Environment to Economy -- for the treatment of natural resource inputs used by aquaculture
• TG-3.4 Flows from Economy to Environment -- for the recording of aquaculture residual flows to the environment
• TG-2.7 Pollution Flows -- for nutrient and chemical emission accounting relevant to aquaculture environmental pressures

3. Guidance Material

Aquaculture has experienced rapid global growth, with production exceeding wild-capture fisheries for human consumption in recent years^[2]. This expansion creates accounting challenges that differ fundamentally from those of traditional fisheries. While wild-capture fisheries involve the extraction of natural biological resources from common-pool stocks, aquaculture involves deliberate cultivation under the direct control, responsibility and management of institutional units. This distinction places aquaculture firmly within the production boundary of the national accounts, with significant implications for how aquaculture stocks and their changes are recorded.

This Circular is foundational for TG-6.8 Aquaculture Thematic Methods and complements TG-3.1 Asset Accounts, addressing the interface between produced and non-produced assets that is particularly complex in the marine domain. The relationship between aquaculture accounting and fisheries management is addressed in TG-1.5 OA and Fisheries Management, which clarifies how cultivated and natural aquatic resources interact within integrated ocean accounting frameworks.

This section examines the production boundary treatment (Section 3.1), compilation procedures for aquaculture accounts (Section 3.2), asset classification for aquaculture stocks (Section 3.3), carrying capacity considerations for sustainable production (Section 3.4), and environmental interactions (Section 3.5). Section 3.6 presents worked examples demonstrating account compilation with synthetic data. The guidance presented here aligns with the SEEA Central Framework, the SEEA Agriculture, Forestry and Fisheries (SEEA AFF), and the 2025 SNA treatment of cultivated biological resources.

3.1 Production Boundary Treatment

The distinction between aquaculture and wild-capture fisheries is fundamental to their accounting treatment. This distinction rests on the production boundary--the demarcation between economic activity that is treated as production and natural processes that are outside the production boundary^[3]. For comprehensive guidance on the relationship between natural and produced assets, see TG-3.1 Asset Accounts Section 3.3.1 (Aquatic resources) and Section 3.5 (Produced Assets in the Ocean Domain).

The production boundary and aquaculture

The SEEA Central Framework establishes that "the production boundary includes all activities carried out under the responsibility, control and management of a resident institutional unit in which labour and assets are used to transform inputs of goods and services into outputs of other goods and services"^[4]. Applying this principle to aquatic resources, the SEEA CF states that "the growth of fish in fish farms and other aquaculture facilities is treated as a process of production"^[5].

The FAO definition of aquaculture, adopted in the SEEA CF, provides the operational basis for this distinction:

"Aquaculture is 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. For statistical purposes, aquatic organisms that are harvested by an individual or corporate body that has owned them throughout their rearing period contribute to aquaculture, while aquatic organisms that are exploitable by the public as a common property resource, with or without appropriate licences, are the harvest of fisheries."^[6]

This definition establishes three key criteria for treating aquatic production as aquaculture: (1) intervention in the rearing process; (2) ownership of the stock; and (3) ownership throughout the rearing period. These criteria provide a practical basis for classification, though edge cases remain. For extensive pond culture systems with minimal intervention, or ranching programmes with delayed harvest, the SEEA AFF paragraphs 2.127--2.129 provide additional guidance on distinguishing natural from cultivated processes. In general, where there is a clear institutional unit exercising control over the growth process--even if that control is limited to stocking and harvesting--the activity should be treated as aquaculture^[7].

Table 3.9.1: Aquaculture production boundary decision criteria

This decision table summarises the key distinguishing characteristics that determine whether aquatic resources fall on the natural or cultivated side of the production boundary. In practice, some operations may exhibit characteristics from both columns, requiring case-by-case assessment against the three criteria established above.

Implications for accounting treatment

The placement of aquaculture within the production boundary has several important implications:

Output measurement. The growth of aquaculture organisms constitutes output in the national accounts sense. This growth is recorded as production of the aquaculture industry, contributing to GDP and value added. In contrast, the natural growth of wild fish stocks is not considered production and does not contribute directly to economic output--only the extraction (harvest) enters the economic accounts^[8]. For guidance on how natural resource extraction is treated, see TG-3.2 Flows from Environment to Economy. The industry classification of aquaculture within the ocean economy is addressed in TG-3.3 Economic Activity Relevant to the Ocean.

Asset classification. Aquaculture stocks are classified as produced assets rather than natural resources. This contrasts with wild fish stocks, which are classified as natural (non-produced) assets subject to depletion accounting. The distinction between produced and non-produced assets affects balance sheet treatment and the calculation of depletion-adjusted income measures^[9]. The framework for natural aquatic resource accounting is presented in TG-3.1 Asset Accounts Section 3.3.1.

Capital formation. Investment in aquaculture stocks is recorded as gross fixed capital formation (for breeding stocks) or changes in inventories (for stocks being raised for harvest). This treatment parallels the accounting for livestock in agriculture, where breeding cattle are treated as fixed assets and animals raised for slaughter are treated as inventories^[10].

Mixed and transitional cases

The SEEA CF recognises that not all cases are straightforward. Some aquatic resources may begin life in aquaculture facilities before release to the wild, while others may be captured wild and transferred to aquaculture for further growth^[11]. The SEEA CF recommends that "the proportion of growth in the wild and the proportion of growth in aquaculture facilities should be separated and classified appropriately"^[12].

For ranching and enhancement programmes, where cultured seeds or juveniles are released into the wild for capture at a later stage, the released organisms should be recorded as a reclassification from cultivated to natural aquatic resources. Conversely, wild-caught organisms introduced into aquaculture facilities should be recorded as a reclassification in the opposite direction^[13]. The treatment of reclassifications is consistent with the general asset account framework in TG-3.1 Asset Accounts Section 3.1. Ranching and stock enhancement programmes often involve fisheries management objectives alongside commercial aquaculture; the accounting treatment should be consistent across both contexts, and TG-1.5 OA and Fisheries Management addresses the fisheries management perspective on these programmes.

The 2025 SNA provides additional guidance on the treatment of biological resources at the boundary: "In practice, it may be difficult to make a clear distinction between cultivated and non-cultivated biological resources... The former resources generally take place under the direct control, responsibility and management of institutional units, and are treated as assets"^[14]. For aquatic resources, the SNA specifically notes that "animals for slaughter and plants and crops which are produced on farms (including fish farms)" are clearly under direct control and thus treated as cultivated^[15].

3.2 Compilation Procedure

This section provides a step-by-step procedure for compiling aquaculture accounts, integrating production accounts, asset accounts, and environmental flow accounts. The procedure assumes that countries have established coordination mechanisms between statistical offices, aquaculture regulatory agencies, and environmental authorities as described in TG-0.1 General Introduction to Ocean Accounts Section 4.

Step 1: Delineate aquaculture operations and classify systems

Identify all aquaculture operations within the national accounting boundary and classify them according to:

a) System type--open systems (cage culture, net-pens, on-bottom culture), closed systems (tanks, raceways, recirculating aquaculture systems), or semi-intensive systems (pond culture, integrated systems);

b) Species or species groups--finfish (salmon, sea bass, tuna), crustaceans (shrimp, prawns), molluscs (oysters, mussels), aquatic plants (seaweed);

c) Salinity--marine aquaculture (operating in coastal waters or offshore), brackish water aquaculture, or freshwater aquaculture (the latter is outside the ocean accounting boundary but may be included in national aquaculture accounts);

d) Purpose--food production, ornamental species, stock enhancement/ranching (see Section 3.1 for treatment of transitional cases).

Data sources include aquaculture licensing registries, fisheries statistical databases (FAO FishStatJ provides national production data), remote sensing analysis for spatial extent of cage culture operations (TG-4.1 Remote Sensing and Geospatial Data), and industry census data from statistical offices.

Step 2: Compile production accounts

Assemble aquaculture production data following the Supply and Use Table (SUT) framework described in TG-3.3 Economic Activity Relevant to the Ocean:

a) Output--Record aquaculture production in physical terms (tonnes live weight) and monetary terms (value at basic prices). Output includes both harvest for sale and intermediate transfers between hatcheries and grow-out operations.

b) Intermediate consumption--Record feed inputs (fishmeal, fish oil, plant-based feeds), fingerlings/juveniles purchased from hatcheries, veterinary services, energy inputs, and other operational inputs. Feed inputs from wild fisheries should be separately identified to enable calculation of fish-in-fish-out ratios (Section 3.5).

c) Value added--Calculate gross value added as output minus intermediate consumption. This measures the aquaculture sector's contribution to GDP.

d) Employment--Record full-time equivalent employment in aquaculture to enable productivity analysis.

Data sources include aquaculture production surveys, business censuses, industry association reports, feed sales data, and energy consumption statistics.

Step 3: Compile physical asset accounts for aquaculture stocks

Construct physical asset accounts for cultivated aquatic resources following the structure in Section 3.3 below:

a) Opening stock--Determine stock biomass at the beginning of the accounting period from aquaculture facility records, regulatory reporting systems, or statistical surveys. For breeding stocks, record number of broodstock by species. For growing stocks, record total biomass by species and cohort/size class where data permit.

b) Additions to stock--Record natural growth (biomass increase from feeding and maturation), hatchery production or purchases of juveniles (additions to growing stocks), and reclassifications from natural resources (wild-caught organisms introduced for fattening or broodstock).

c) Reductions in stock--Record harvest (sales or transfers to processing), normal losses (routine mortality from disease, predation, environmental stress), catastrophic losses (disease outbreaks, harmful algal blooms, storm damage), escapes (reclassifications to natural resources), and culling (removal of unproductive broodstock).

d) Closing stock--Verify that closing stock equals opening stock plus additions minus reductions. Reconcile discrepancies through data quality audits.

Data sources include aquaculture facility production records, hatchery sales records, veterinary health reports, loss event reporting systems, and regulatory compliance data. For data quality considerations, see TG-0.7 Quality Assurance.

Step 4: Compile monetary asset accounts

Value aquaculture stocks following standard SNA principles for produced assets:

a) Inventory valuation--For growing stocks, apply current market prices to biomass estimates, adjusted for size class if market prices vary by size. Where growth is non-linear or mortality is significant, apply the cost accumulation method described in SEEA AFF para 11.227, recording costs incurred (feed, juveniles, labor, capital services) as the inventory builds up over the growth cycle.

b) Breeding stock valuation--Value breeding stocks based on expected future economic benefits from their reproductive capacity. Apply depreciation to reflect declining productivity as broodstock age. Market values for replacement broodstock may be used where active markets exist.

c) Revaluations--Record holding gains or losses reflecting price changes during the accounting period, separate from volume changes.

For valuation methodology, see TG-1.9 Valuation.

Step 5: Compile environmental flow accounts

Record flows between aquaculture operations and the environment following the methodology in TG-3.2 Flows from Environment to Economy and TG-3.4 Flows from Economy to Environment:

a) Natural inputs--Record abstraction of marine or coastal water for land-based systems (cubic metres), use of wild fish for feed inputs (tonnes, distinguished from commercial fishmeal purchases to avoid double-counting), and where quantifiable, ecosystem services supporting aquaculture (water quality maintenance, nursery habitat provision).

b) Residual outputs--Record nutrient emissions (nitrogen and phosphorus from uneaten feed, faeces, excretion--measured in tonnes N and P), chemical releases (therapeutants, antifoulants--kilograms active ingredient), organic waste deposition (tonnes organic matter), and escapes (number or biomass, classified by species).

c) Spatial attribution--Assign emissions and environmental pressures to receiving ecosystems or management zones to enable integration with ecosystem condition accounts (TG-3.1 Asset Accounts Section 3.4.2).

Data sources include environmental monitoring programs, aquaculture environmental impact assessments, nutrient budget models for cage culture operations, veterinary chemical use records, and escape event reporting systems. See TG-2.7 Pollution Flows for emission accounting methodology.

Step 6: Assess carrying capacity and sustainability indicators

Integrate aquaculture accounts with ecosystem accounts to assess sustainability:

a) Stocking density analysis--Compare actual stocking levels against recommended carrying capacity thresholds for different system types and species. Excessive stocking reduces growth rates, increases disease risk, and elevates environmental pressures.

b) Feed conversion efficiency--Calculate feed conversion ratios (FCR--mass of feed per mass of production) and fish-in-fish-out ratios (FIFO--mass of wild fish in feed per mass of farmed output) as indicators of resource efficiency. See TG-2.11 Resource Efficiency for indicator methodology.

c) Environmental pressure indicators--Calculate nutrient loading per unit area of coastal zone, sediment organic enrichment indices beneath cage sites, and chemical loading. Compare against water quality standards or ecosystem health thresholds from TG-2.1 Biophysical Indicators.

d) Habitat conversion tracking--Where aquaculture expansion involves coastal habitat conversion (mangrove clearance for pond construction, seagrass loss beneath cage moorings), record extent changes in ecosystem accounts for affected habitats. See TG-6.2 Mangrove and Wetland Accounts for mangrove accounting methodology.

e) GBF Target 10 alignment--Report area under sustainable aquaculture management regimes (certified operations, integrated multi-trophic aquaculture systems, operations meeting environmental performance standards) to track progress toward ensuring all aquaculture is under effective management that minimizes impacts on biodiversity and ecosystem functions^[16].

Step 7: Integration and consistency checks

Ensure internal consistency and integration across account types:

a) Production-asset consistency--Verify that harvest recorded in production accounts equals reductions from harvest in asset accounts. Reconcile discrepancies through improved measurement or identification of unrecorded flows.

b) Feed flow consistency--Ensure that wild fish used for feed recorded in aquaculture intermediate consumption matches extractions recorded in fisheries accounts (TG-1.5 OA and Fisheries Management).

c) Ecosystem integration--Link aquaculture environmental pressures (nutrient loading, habitat conversion) to changes in ecosystem condition indicators for receiving ecosystems. Declining condition in coastal ecosystems may signal that aquaculture intensity exceeds ecological carrying capacity.

d) Temporal consistency--Maintain consistent time series by adjusting for changes in system boundaries, classification, or measurement methodology. Document adjustments in metadata following TG-0.7 Quality Assurance standards.

This compilation procedure provides the foundation for policy-relevant analysis, enabling governments to assess whether aquaculture expansion is sustainable, identify environmental pressure points requiring management intervention, and track progress toward blue economy and biodiversity targets.

3.3 Asset Classification

The classification of aquaculture assets must distinguish between different types of aquaculture systems and different categories of aquaculture stocks within those systems. This section builds on the general asset classification framework in TG-3.1 Asset Accounts Section 3.3.

Classification of aquaculture systems

The SEEA CF recognises that "not all aquaculture is undertaken in the same way"^[17]. Key distinctions include:

Open systems (cage culture, net-pen culture, on-bottom culture) involve raising organisms in netted areas within natural water bodies--rivers, coastal waters, or offshore marine environments. In these systems, there is interaction between the cultivated organisms and the surrounding aquatic environment. Water flows through the system, and feed, waste, and organisms may be exchanged with the environment.

Closed systems (tanks, raceways, recirculating aquaculture systems) involve raising organisms in contained facilities that are largely isolated from natural water bodies. Water is typically treated and recirculated, with minimal exchange with the external environment.

Semi-intensive and extensive systems include pond culture and integrated systems where natural productivity contributes to organism growth alongside supplementary feeding.

The SEEA CF notes that "it may be the case that some cultivated aquatic resources should not be considered environmental assets" where they are "entirely removed from a natural environment"^[18]. However, for accounting purposes, all cultivated aquatic resources remain within the scope of aquaculture regardless of the production system employed. The distinction becomes relevant when considering environmental interactions (Section 3.5) and for the ecosystem integration approaches in TG-6.8 Aquaculture Thematic Methods.

Classification of aquaculture stocks

Within aquaculture operations, stocks must be classified according to their function in the production process:

Breeding stocks (fixed assets). Aquatic organisms maintained for reproduction purposes are treated as fixed assets in the SNA classification^[19]. These resources yield repeat products (eggs, juveniles, milt) over multiple production cycles. In asset accounts, they are recorded separately from stocks held for sale, and their growth is recorded as gross fixed capital formation. The 2025 SNA confirms that "animal resources yielding repeat products" include "aquatic resources maintained for controlled reproduction"^[20].

Growing stocks (inventories). Organisms being raised for eventual harvest and sale are treated as inventories, specifically as work-in-progress^[21]. The growth of these organisms over the accounting period represents additions to inventory, while harvest represents withdrawals. The SEEA CF notes that "the majority of changes in the stock of cultivated aquatic resources should be accounted for as changes in inventories"^[22].

Hatchery output. The treatment of hatchery production deserves specific attention. Juvenile organisms produced by hatcheries and sold to grow-out operations represent output of the hatchery industry. This involves a transfer from work-in-progress at the hatchery to work-in-progress at the grow-out facility. The transaction should be recorded as a sale and purchase of goods (intermediate consumption by the grow-out operation), rather than as a reclassification between asset categories, since ownership changes hands through a market transaction. This treatment is consistent with the SNA recording of sales of livestock between agricultural establishments^[23].

Physical asset account structure

Table 3.9.2 presents the structure of a physical asset account for cultivated aquatic resources, following the format in SEEA CF Table 5.22.

Table 3.9.2: Structure of physical asset account for cultivated aquatic resources

This structure parallels the asset account for natural aquatic resources presented in TG-3.1 Asset Accounts Table 1, enabling side-by-side comparison and consolidation of total aquatic resource accounts.

Growth in stock encompasses both increase in numbers (through hatching, natural reproduction where relevant) and increase in biomass (growth of individual organisms). For breeding stocks, only the growth of the breeding population is recorded; the juveniles produced are recorded as additions to growing stocks.

Reclassifications record transfers between natural and cultivated categories. Introduction of wild-caught organisms as broodstock or seed represents a reclassification from natural to cultivated resources. Release of cultured organisms for ranching or enhancement programmes, and escapes from aquaculture facilities, represent reclassifications from cultivated to natural resources^[24].

Harvest records the removal of organisms from growing stocks for sale or processing. For breeding stocks, animals removed for slaughter (culling of unproductive or excess broodstock) are recorded as reductions.

Normal losses include mortality from routine causes such as disease, predation, and environmental stress within normal operating parameters.

Catastrophic losses record exceptional losses from disease outbreaks, harmful algal blooms, extreme weather events, or other unexpected events beyond normal operating expectations^[25].

Monetary valuation

Aquaculture stocks are valued following standard SNA principles for produced assets. For inventory valuation, the SEEA AFF notes that "in the case of trees, a distribution of output over the accounting periods of the growth of the trees in proportion to the costs incurred may also not provide satisfactory results when looking at individual generations"^[26]. Similar challenges arise for aquaculture, where growth is not linear and significant mortality may occur. For comprehensive guidance on valuation approaches, see TG-1.9 Valuation.

For breeding stocks (fixed assets), valuation should reflect the expected future economic benefits from the breeding capacity. Depreciation is recorded for the decline in value as breeding animals age and their productive capacity declines^[27].

3.4 Carrying Capacity Considerations

Aquaculture production occurs within environmental constraints that determine the sustainable level of production. Understanding and accounting for these constraints is essential for assessing the long-term viability of aquaculture operations and their interactions with marine ecosystems.

Concept of carrying capacity in aquaculture

The concept of carrying capacity in aquaculture contexts refers to the maximum production that can be sustained in a given environment without causing unacceptable environmental impacts or production failures. The ISIC Rev.4 definition of aquaculture explicitly references this concept, describing aquaculture as "the production process involving the culturing or farming... of aquatic organisms... using techniques designed to increase the production of the organisms in question beyond the natural capacity of the environment (for example regular stocking, feeding and protection from predators)"^[28].

Several dimensions of carrying capacity are relevant for accounting purposes:

Physical carrying capacity refers to the maximum stocking density or production that can be achieved given physical and biological constraints (space, oxygen, water flow, etc.).

Production carrying capacity refers to the level of production at which marginal costs equal marginal revenues--the economically optimal production level given input costs and output prices.

Ecological carrying capacity refers to the level of production that can be sustained without causing unacceptable impacts on the surrounding environment or wild populations. This is particularly relevant for open aquaculture systems that interact with marine ecosystems.

Social carrying capacity refers to the level of production that is acceptable given competing uses of coastal and marine space and community concerns about environmental and aesthetic impacts.

This carrying capacity framework draws on aquaculture science literature and is presented here as a practical interpretation for accounting purposes. The Statistical Framework for Measuring the Sustainability of Tourism (SF-MST) provides a parallel treatment of carrying capacity in its discussion of tourism environmental limits (para 4.103), supporting the broader applicability of carrying capacity concepts within environmental-economic accounting^[29]. The SEEA AFF notes that asset accounts "can be used to better understand the carrying capacity of agricultural areas with respect to livestock, for example, the number of cattle per hectare"^[30], providing a direct statistical precedent for applying carrying capacity analysis to cultivated biological resources.

Accounting implications

For accounting purposes, carrying capacity considerations affect the interpretation of production levels and the assessment of sustainability:

Stock assessment. The opening and closing stocks of cultivated aquatic resources should be assessed against the carrying capacity of the facilities and environment. Stocking at levels that exceed carrying capacity may lead to reduced growth rates, increased mortality, disease outbreaks, and environmental degradation.

Sustainable yield. While the concept of maximum sustainable yield (MSY) is traditionally applied to wild fisheries (see TG-6.7 Fisheries Stock Assessment), analogous concepts apply to aquaculture in open systems. Production that exceeds ecological carrying capacity may degrade the supporting ecosystem, reducing its capacity to support future production.

Environmental condition. For open aquaculture systems operating within marine ecosystems, the ecosystem condition accounts described in TG-3.1 Asset Accounts Section 3.4.2 should capture changes in environmental quality that affect or are affected by aquaculture operations.

Integration with ecosystem accounts

The SEEA Ecosystem Accounting framework provides a basis for linking aquaculture accounts with ecosystem condition and service accounts. Key linkages include:

Supporting services. Marine ecosystems provide water quality maintenance, waste assimilation, and habitat functions that support aquaculture production. Degradation of these supporting services may reduce carrying capacity and production potential.

Provisioning services. In some extensive aquaculture systems, natural productivity contributes directly to fish growth, representing a flow of ecosystem services to the aquaculture activity.

Regulating services. Ecosystems regulate water temperature, disease prevalence, and harmful algal blooms, all of which affect aquaculture production.

For guidance on ecosystem service accounting, see TG-3.2 Flows from Environment to Economy and TG-2.4 Ecosystem Goods and Services.

3.5 Environmental Interactions

Aquaculture, particularly in open marine systems, involves significant interactions with the surrounding environment. These interactions must be captured in ocean accounts to provide a complete picture of the aquaculture sector's environmental dependencies and impacts. This section complements the general guidance on environmental flows in TG-3.2 Flows from Environment to Economy and TG-3.4 Flows from Economy to Environment.

Inputs from the environment

Aquaculture operations draw upon environmental inputs that should be recorded in physical supply and use accounts:

Water abstraction. Land-based aquaculture systems (tanks, ponds, raceways) may abstract significant volumes of freshwater or seawater. These abstractions should be recorded in water accounts following the methodology in SEEA-Water^[31]. For marine cage culture, the use of ocean water is not typically recorded as abstraction given the open nature of the system, but water quality requirements should be noted.

Feed from wild fisheries. A significant environmental interaction is the use of fish meal and fish oil derived from wild-caught fish as feed inputs for carnivorous aquaculture species^[32]. The SEEA AFF notes that "fish products 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"^[33].

This creates a linkage between aquaculture production and wild fish stocks that should be reflected in integrated accounts. The feed conversion ratio (FCR)--the ratio of feed input to fish output--is a key indicator of the efficiency of this transformation. For supply and use accounting, the feed inputs (measured in tonnes of feed or fish equivalent) should be recorded as intermediate consumption by the aquaculture industry.

The fish-in-fish-out ratio (FIFO)--the ratio of wild fish used in feed to farmed fish produced--is increasingly used alongside FCR to assess the net contribution of aquaculture to global seafood supply. Where FIFO exceeds 1.0, aquaculture is a net consumer of wild fish; where it falls below 1.0, aquaculture provides a net addition to fish protein supply. FIFO ratios vary substantially by species: herbivorous species such as tilapia and carp have ratios well below 1.0, while carnivorous species such as salmon and marine finfish may have ratios above 1.0, though these have been declining with improvements in feed technology^[34]. For resource efficiency analysis, see TG-2.11 Resource Efficiency.

Ecosystem services. As noted in Section 3.4, aquaculture benefits from ecosystem services including water quality maintenance, disease regulation, and larval supply (for some species). These services represent flows from the environment to the economy that may be captured in ecosystem service accounts.

Outputs to the environment

Aquaculture operations generate outputs to the environment that should be recorded in residual flow accounts:

Nutrient loading. Aquaculture releases nutrients (primarily nitrogen and phosphorus) through uneaten feed, faeces, and metabolic excretion. In open systems, these nutrients are released directly to the marine environment and may contribute to eutrophication in poorly flushed areas^[35]. Nutrient releases should be recorded in emission accounts following the SEEA CF methodology for residual flows. For guidance on pollution flow accounting, see TG-2.7 Pollution Flows.

Organic matter. Feed waste and faeces settling beneath cage sites can alter benthic conditions, affecting sediment chemistry and benthic communities.

Chemical releases. Aquaculture may involve use of therapeutants (antibiotics, parasiticides), antifoulants, and other chemicals that are released to the environment. These should be recorded following standard emission accounting principles.

Escapes. Organisms that escape from aquaculture facilities represent a flow from the economy to the environment. As noted in Section 3.3, these should be recorded as reclassifications from cultivated to natural aquatic resources "in cases where the fish are able to integrate into natural fish stocks"^[36]. Where integration is not possible (e.g., non-native species in unsuitable environments), escapes should be recorded as losses.

Pathogen and parasite transmission. Aquaculture operations may affect wild populations through disease and parasite transmission, an interaction that is difficult to quantify but relevant to ecosystem condition assessment.

Recording environmental interactions

Table 3.9.3 presents a framework for recording key environmental interactions of aquaculture in physical terms.

Table 3.9.3: Framework for recording environmental interactions of aquaculture

Integration with flows accounts

The environmental interactions of aquaculture should be integrated with the flow accounts described in TG-3.2 Flows from Environment to Economy and TG-3.4 Flows from Economy to Environment. This integration enables:

• Calculation of resource efficiency indicators (e.g., water use per tonne of production, feed conversion ratios)--see TG-2.11 Resource Efficiency
• Assessment of environmental pressures relative to ecosystem carrying capacity
• Linking of aquaculture activity to changes in ecosystem condition--see TG-2.1 Biophysical Indicators
• Derivation of sustainability indicators for aquaculture management

For detailed methodological guidance on site-specific assessment and integration with ecosystem accounts, see TG-6.8 Aquaculture Thematic Methods. The broader relationship between aquaculture and fisheries within ocean accounting is addressed in TG-1.5 OA and Fisheries Management, which discusses how aquaculture and wild-capture fisheries interact in contributing to ocean-based food production and how both are treated within integrated fisheries governance frameworks.

3.6 Worked Examples

This section presents three worked examples with synthetic data demonstrating the compilation of aquaculture accounts for common scenarios: a shrimp farm production account, a coastal zone mangrove conversion tracking system, and a salmon cage culture nutrient loading assessment.

Example 1: Coastal shrimp farm production and asset accounts

Context: A coastal nation operates intensive shrimp aquaculture in converted mangrove areas. The example demonstrates production account compilation, asset account structure for growing stocks, and feed flow tracking.

Scenario parameters (synthetic data for accounting year 2025):

• Total shrimp farm area: 500 hectares
• Growing stocks opening biomass: 800 tonnes
• Stocking during year: 1,200 tonnes post-larvae (PL) purchased from hatcheries
• Biomass growth: 3,500 tonnes (from feeding and maturation)
• Harvest: 3,800 tonnes (market-size shrimp)
• Normal losses: 600 tonnes (mortality from disease, predation)
• Catastrophic losses: 100 tonnes (disease outbreak in one farm cluster)
• Closing biomass: 1,000 tonnes
• Feed inputs: 6,000 tonnes commercial feed (25% fishmeal content = 1,500 tonnes fishmeal from wild fisheries)
• Production value: $38 million at basic prices
• Intermediate consumption: $22 million (feed $15 million, PL $3 million, other $4 million)
• Value added: $16 million

Table 3.9.4: Shrimp aquaculture physical asset account, 2025

Verification: Closing stock (1,000) = Opening stock (800) + Additions (4,700) - Reductions (4,500). Account balances correctly.

Feed conversion and efficiency indicators:

• Feed conversion ratio (FCR) = Feed input / Harvest = 6,000 / 3,800 = 1.58 (industry benchmark for intensive shrimp: 1.5-2.0)
• Fish-in-fish-out ratio (FIFO) = Fishmeal input / Harvest = 1,500 / 3,800 = 0.39 (net contributor to seafood supply, as FIFO < 1.0)

Production account linkages: The 3,800 tonnes harvest recorded as reduction in asset account should match output recorded in supply table for ISIC 0322 (Marine aquaculture). The $3 million PL purchases appear as intermediate consumption in the shrimp farm production account and as output in the hatchery industry production account.

Environmental flow implications: The 1,500 tonnes of wild fish embodied in feed creates a linkage to wild fishery extraction accounts. This should be recorded as natural input in TG-3.2 Flows from Environment to Economy, connecting aquaculture production to wild fish stock depletion.

Example 2: Mangrove conversion tracking for shrimp pond expansion

Context: The same coastal nation experienced shrimp aquaculture expansion from 2020-2025, involving conversion of mangrove ecosystems to pond culture. The example demonstrates integration of aquaculture asset accounts with ecosystem extent accounts.

Scenario parameters (synthetic data):

• Mangrove extent 2020: 12,000 hectares
• Mangrove extent 2025: 11,500 hectares
• Shrimp pond extent 2020: 300 hectares
• Shrimp pond extent 2025: 500 hectares
• Documented mangrove-to-pond conversion 2020-2025: 200 hectares
• Other mangrove losses (erosion, development): 300 hectares

Table 3.9.5: Ecosystem extent account for mangrove and shrimp pond ecosystems, 2020-2025

Cross-account consistency: The 200 hectares of mangrove-to-pond conversion appears as a reduction in the mangrove extent account and as an addition to the shrimp pond (produced asset) area. This reclassification tracks the transformation of natural ecosystem assets into cultivated aquaculture infrastructure.

Policy implications: The 4.2% loss of mangrove extent over five years signals environmental pressure from aquaculture expansion. Mangrove ecosystem service losses include carbon sequestration capacity (estimated 3-5 tonnes CO2e/ha/yr), coastal protection value, and nursery habitat for wild fisheries. See TG-6.2 Mangrove and Wetland Accounts for comprehensive mangrove accounting methodology, including valuation of ecosystem services lost through conversion.

GBF Target 10 relevance: Countries reporting under the Kunming-Montreal Global Biodiversity Framework must track area under sustainable aquaculture. The 200-hectare mangrove conversion would need to be balanced by demonstrating that the resulting shrimp farms meet environmental sustainability criteria to avoid negative reporting against biodiversity targets.

Example 3: Salmon cage culture nutrient loading to coastal ecosystem

Context: A temperate coastal nation operates salmon cage culture in fjords and sheltered coastal waters. The example demonstrates compilation of nutrient emission accounts and integration with ecosystem condition assessment.

Scenario parameters (synthetic data for accounting year 2025):

• Salmon production: 150,000 tonnes live weight harvest
• Feed input: 195,000 tonnes (FCR = 1.3)
• Feed composition: 30% protein, 20% fat, nitrogen content 4.8% of feed, phosphorus content 0.9%
• Estimated nutrient releases:
  • Nitrogen: 195,000 tonnes feed × 0.048 × 0.65 (release fraction) = 6,084 tonnes N
  • Phosphorus: 195,000 tonnes feed × 0.009 × 0.70 (release fraction) = 1,229 tonnes P
• Receiving coastal ecosystems: 15 fjord systems, total surface area 450 km²

Table 3.9.6: Nutrient emission account for salmon aquaculture, 2025

Nutrient loading intensity:

• Nitrogen loading = 6,084 tonnes / 450 km² = 13.5 tonnes N/km²/yr
• Phosphorus loading = 1,229 tonnes / 450 km² = 2.7 tonnes P/km²/yr

Ecosystem condition linkages: These nutrient loading rates should be assessed against water quality standards and ecosystem condition indicators from TG-2.1 Biophysical Indicators. Indicators might include:

• Dissolved oxygen levels in bottom waters (hypoxia threshold: < 2 mg/L)
• Chlorophyll-a concentrations (eutrophication indicator)
• Benthic community condition indices beneath cage sites

Carrying capacity assessment: If condition indicators show declining trends (increasing hypoxia, benthic degradation), this signals that aquaculture intensity may exceed the ecological carrying capacity of the receiving fjord systems. Authorities may need to adjust licensing to reduce stocking density or redistribute farms to less-impacted areas.

Data sources: Nutrient release estimates are typically derived from mass-balance models combining feed input data (from industry records), feed composition (from nutritional analysis), and empirically-determined release fractions (from scientific literature or site-specific monitoring). For emission accounting methodology, see TG-2.7 Pollution Flows and TG-3.4 Flows from Economy to Environment.

Cross-stack connections: These worked examples demonstrate integration across the accounting stack:

• Upward to TG-1.x policy: Mangrove conversion and nutrient loading evidence informs decisions on aquaculture zoning, licensing thresholds, and environmental performance standards (TG-1.2 Blue Economy Policy, TG-1.5 OA and Fisheries Management).
• Lateral to TG-2.x indicators: FCR and FIFO ratios feed into resource efficiency indicators (TG-2.11); nutrient loading drives water quality indicators (TG-2.1).
• Downward to TG-4.x data: Extent mapping requires remote sensing and geospatial analysis (TG-4.1); nutrient budget models require data integration from production statistics, feed composition databases, and field monitoring (TG-4.2 Data Integration).

4. 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 a priority addition identified in the February 2025 modular structure revision.

5. References