Popularity and parity: towards more inclusive and balanced aquaculture

doi:10.21203/rs.3.rs-2806743/v1

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Popularity and parity: towards more inclusive and balanced aquaculture

https://doi.org/10.21203/rs.3.rs-2806743/v1

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Aquaculture is an emerging, fast-growing, and diverse food production system that could enhance food security and nutrition and add resilience to the global food system. Yet imbalanced aquaculture growth has resulted in a highly uneven distribution of aquaculture production among countries, which is essentially a lack of diversity in the source of aquaculture production. While the issue has been recognized as an undesirable feature of aquaculture development, there has yet to be a comprehensive assessment, not even a formal measure of such imbalance. This paper develops an indicator system to assess production distribution among countries and regions. The assessment framework uses the “effective number of countries” (ENC) as a diversity measure and extends it into two key indicators (i.e. popularity and parity) to measure the inclusiveness of a production system and the balance of production distribution. The assessment reveals that global aquaculture development 1970–2020 has raised its overall popularity to a high plateau (~ 85 percent) thanks to finfish farming, yet aquaculture popularity still has much room to grow for nearly all 43 species groups examined here. While the inclusive yet imbalanced aquaculture growth has reduced global aquaculture parity to below 3 percent, aquaculture has experienced a balanced growth in most of all 85 country groups examined, and the global parity has been on an upward trend since the new millennium 2000–2020. However, in most of the 85 country groups, the parity of aquaculture is still much lower than those of capture fisheries and terrestrial meat production, indicating that low aquaculture parity cannot be fully attributed to discrepancies in countries’ characteristics, such as geographic location and climate, resource endowments, demographics, socioeconomic conditions, and development status. The highly uneven distribution of aquaculture production could undermine its widely expected role in enhancing food security and nutrition, and weaken the resilience of the global food system against various risks. The unevenness, however, indicates a large untapped potential for further aquaculture growth. Aquaculture popularity and parity could be mainstreamed as performance indicators in policymaking and sector management to facilitate more inclusive aquaculture development, enhance the resilience of the global food system, and unlock aquaculture growth potential. The indicator system can be applied in sector assessment and monitoring of any sector or at different levels (e.g. subnational). While only key findings are highlighted in the main text, the comprehensive results of the assessment is documented in the supplementary materials to facilitate further study.

Social science/Development studies

Social science/Economics

Social science/Business and management

aquaculture

sector assessment

uneven production distribution

effective number of countries

popularity

parity

Perennial concerns over food security and nutrition, together with the pressures of population growth, climate change, and other challenges, have drawn increasing attention to the potential of aquatic food production, particularly through aquaculture^1–8. As one of the fastest growing food sectors, global aquaculture production has multiplied over 30-fold from 3.7 million tonnes in 1970 to 123 million tonnes in 2020, thanks to aquaculture expansion in nearly 200 countries (including non-sovereign territories)⁹. However, 96 percent of the growth was driven by only 20 countries, and the imbalanced growth has resulted in a highly uneven global aquaculture. In 2020, 90 percent of world aquaculture production came from only 10 countries, and the largest producer alone contributed 57 percent. In contrast, the contribution of the top 10 countries was 57 percent in capture fisheries (15 percent from the first-ranked country) and 62 percent in terrestrial meat production (23 percent from the first-ranked country).

The highly uneven distribution of global production has been recognized as an undesirable feature of aquaculture development, reflecting unfulfilled aquaculture aspirations in many countries¹⁰. Ignoring this imbalance, which is often overshadowed by the sector’s impressive overall performance, could lead to unnecessary complacency, resulting in misguidance or missed opportunities in policy and planning^11,12.

While the uneven distribution of aquaculture production among countries and regions has been routinely monitored in the Food and Agriculture Organization of the United Nations (FAO) biennial flagship reports on the State of World Fisheries and Aquaculture (e.g. ref. 10, p.28), there has yet to be a comprehensive assessment. No formal measure has been developed to quantify the imbalance, which is usually assessed by ad hoc observations of the distribution of aquaculture production among countries or regions^10,12, such as the comparison of top producers’ shares in the preceding paragraph.

Aquaculture is often deemed a most diverse food production system that could add resilience to the global food system¹³, yet the uneven production distribution, which is essentially a lack of diversity in the sources of aquaculture production, has received little attention in research on diversity in agricultural systems (including aquatic food production)¹⁴.

Here we conduct a systematic, quantitative assessment of the distribution of aquaculture production among countries and regions. Based on the effective number of countries (ENC) as a diversity measure, we develop an assessment framework that comprises 10 indicators, with a focus on four of them: popularity, parity, as well as the latter’s intra- and inter-regional components. The popularity of aquaculture measures the inclusiveness of aquaculture among countries, while the parity captures the inclusiveness as well as the evenness of production distribution among existing aquaculture countries.

We use the indicator system to assess the status and trends of aquaculture popularity and parity during 1970–2020, with a focus on the recent two decades (2000–2020). We examine the aquaculture imbalance not only in the world as a whole but also in another 84 country groups, with a focus on 27 geographic groups (including five regions and 22 sub-regions). We also look into the popularity and parity of aquaculture in 43 aquatic species groups, including five major species groups (finfish, crustaceans, molluscs, miscellaneous aquatic animals and animal products, and algae) and their subgroups. As aquaculture imbalance could reflect different characteristics among countries, we use the parities of other food production systems (i.e. capture fisheries and terrestrial meat production) as benchmarks to take a deeper look at aquaculture parity.

Our in-depth assessment generates a wealth of information and insights. We highlight key stylized facts in the main text and document the comprehensive results in supplementary materials. The implications of these results are discussed in the last section.

2.1 A 10-indicator system for assessment of production distribution among countries and regions

For the sake of clarity, we discuss the indicator system mostly as a specific one for assessing the distribution of global aquaculture production among countries and regions. However, the system can be applied to any aquaculture subsector (e.g. finfish farming or tilapia farming), and it can be generalized into an assessment framework for any production system (e.g. capture fisheries or terrestrial meat production) in any country group (e.g. a region or subregion).

2.1.1 Indicator 1: total production as a basic measure of overall performance

The first indicator is global aquaculture production, which is a basic measure of overall aquaculture performance.

2.1.2 Indicator 2: total number of aquaculture countries (n) as a measure of abundance

In a similar way to the total number of species measuring the richness of species in an ecosystem¹⁵, the total number of aquaculture countries (denoted as n) can be used to measure the abundance of aquaculture countries.

2.1.3 Indicator 3: effective number of countries (ENC) as a measure of diversity

The third indicator measures the diversity of aquaculture countries by the “effective number of countries”:

$$\text{E}\text{N}\text{C}=\left\{\begin{array}{c}{e}^{-{\sum }_{i=1}^{n}{s}_{i}\text{ln}\left({s}_{i}\right)}, when n\ge 1\\ 0, when n=0 \end{array}\right.$$

where n (≥ 0) denotes the total number of aquaculture countries; ${s}_{i}$ denotes each country’s share in world aquaculture production; and the summation term is the Shannon–Wiener (entropy) index (a widely used diversity index). Similar to the effective number of species that measures the diversity of species in an ecosystem^16,17 or aquaculture production system^18,19, or the effective number of parties that measures the diversity of political forces in a political system^20,21, the ENC here measures the diversity of national producers in global aquaculture.

By definition, when no country undertakes aquaculture, ENC = n = 0. When there is at least one country practicing aquaculture ($n\ge 1$), ENC ranges between 1 and n. When production is evenly distributed among all aquaculture countries, the effective number of countries is equal to the total number (ENC = n). The more uneven the distribution is, the closer the ENC will be to 1. ENC = 1 when the entire production is concentrated in one country.

2.1.4 Indicators 4 and 5: intra-regional diversity versus inter-regional diversity

The ENC in Eq. (1) can be decomposed into two components:

$$\text{E}\text{N}\text{C}=\text{W}\text{G}\text{E}\text{N}\text{C}\times \text{E}\text{N}\text{C}\text{G}$$

The first component is within-group ENC (WGENC), which is calculated as a weighted geometric mean of ENC within different country groups (denoted as ${\text{E}\text{N}\text{C}}_{j}$). The weight assigned to each group is based on its share in world production (denoted as ${s}_{j}$), i.e.

$$\text{W}\text{G}\text{E}\text{N}\text{C}=\prod _{j}{\left({\text{E}\text{N}\text{C}}_{j}\right)}^{{s}_{j}}$$

The second component (i.e. the effective number of country groups) is

$$\text{E}\text{N}\text{C}\text{G}={e}^{{\sum }_{j}{-s}_{j}\text{l}\text{n}\left({s}_{j}\right)}$$

which measures the evenness of production distribution across given country groups.

The WGENC, ENCG and ENC are equivalent, respectively, to alpha, beta and gamma diversities, which are three measures that are often used to assess biological diversity in an ecosystem^22,23. Cai et al.¹⁹ used similar indicators to measure the diversity of species in aquaculture.

By grouping countries into five geographic regions (Africa, the Americas, Asia, Europe and Oceania), we use the WGENC defined in Eq. (3) as the fourth indicator to measure the intra-regional diversity of aquaculture countries (i.e. the average diversity of aquaculture countries within the five regions). Accordingly, we use the ENCG defined in Eq. (4) as the fifth indicator to measure the inter-regional diversity (i.e. the evenness of the distribution of aquaculture production across the five regions). Therefore,

Global diversity (ENC) = intra-regional diversity (WGENC) × inter-regional diversity (ENCG) (5)

With five regions, the inter-regional diversity (ENCG) ranges between 1 and 5. It is equal to 1 when aquaculture production is entirely concentrated in one region, while it is equal to 5 when the production is evenly distributed across the five regions. Accordingly, the intra-regional diversity (WGENC) ranges from one fifth to 100 percent of the global diversity (ENC).

2.1.5 Indicator 6: popularity

The six indicator is the popularity of aquaculture, which measures the inclusiveness of aquaculture, i.e.

$$\text{P}\text{o}\text{p}\text{u}\text{l}\text{a}\text{r}\text{i}\text{t}\text{y}=n / \stackrel{-}{N}$$

where n is the total number of aquaculture countries, and $\stackrel{-}{N}$ is the number of all countries. The popularity of aquaculture is equal to 100 percent when aquaculture is engaged in all countries, while it is equal to zero when no country undertakes aquaculture.

2.1.6 Indicator 7: evenness

The evenness of species in an ecosystem is often measured by the effective number of species divided by the total number^16,24. Similarly, the evenness of production distribution among existing aquaculture countries can be measured by ENC divided by the total number of aquaculture countries, i.e.

$$\text{E}\text{v}\text{e}\text{n}\text{n}\text{e}\text{s}\text{s}=\text{E}\text{N}\text{C} / n$$

which is the seventh indicator here.

When production is evenly distributed among existing aquaculture countries (i.e. ENC = n), the evenness is 100 percent. As production is concentrated towards one country, the evenness will be approaching to the exclusive lower bound 1/n. Therefore, the lower bound of evenness decreases with the total number of aquaculture countries, which implies that the evenness of aquaculture may tend to decline with its popularity. For example, suppose that there were 10 aquaculture countries with one of them accounting for nearly the entire production, then the evenness would be close to 10 percent. If 10 new countries entered the sector, which did not change the dominance of the top producer (i.e., ENC remained close to 1), then the evenness would drop to approximately 5 percent.

Equation (7) can be transformed into

$$\text{D}\text{i}\text{v}\text{e}\text{r}\text{s}\text{i}\text{t}\text{y} \left(\text{E}\text{N}\text{C}\right)= \text{a}\text{b}\text{u}\text{n}\text{d}\text{a}\text{n}\text{c}\text{e} \left(n\right)\times \text{e}\text{v}\text{e}\text{n}\text{n}\text{e}\text{s}\text{s}$$

which means that the diversity of aquaculture countries (measured by ENC) captures both the abundance of aquaculture countries (measured by n) and the evenness of production distribution among them.

2.1.7 Indicator 8: parity

While all species in an ecosystem contributes to its biomass, not all countries contribute to global aquaculture production. This makes indicator 7 a less adequate measure of the imbalance in aquaculture. For example, suppose that in a region comprised of 50 countries, only two countries practiced aquaculture with equal amount of production. Then the production evenness, as measured in Eq. (7), would be 100 percent, even though the region had a highly imbalanced aquaculture because of low aquaculture popularity (only 4 percent).

To address the inadequacy, we introduce the parity of aquaculture as the eighth indicator, which is calculated by normalizing the diversity of aquaculture against the number of all countries, i.e.

$$\text{P}\text{a}\text{r}\text{i}\text{t}\text{y}=\text{E}\text{N}\text{C} / \stackrel{-}{N}$$

When production is evenly distributed among aquaculture countries (i.e. ENC = n), the parity of aquaculture countries is equal to its popularity (i.e. n /$\stackrel{-}{N}$), which is the upper bound of the parity. When aquaculture production is concentrated towards one country, the parity will be approaching the lower bound 1 / $\stackrel{-}{N}$. Therefore, a country group with a smaller number of countries would have a higher lower bound of aquaculture parity. For example, the lower bound of aquaculture parity is 50 percent for the subregion of Australia and New Zealand, whereas that for Central Asia (5 countries) is 20 percent.

According to equations (6), (7) and (9),

$$\text{P}\text{a}\text{r}\text{i}\text{t}\text{y}=\text{p}\text{o}\text{p}\text{u}\text{l}\text{a}\text{r}\text{i}\text{t}\text{y} \left(\text{i}\text{n}\text{c}\text{l}\text{u}\text{s}\text{i}\text{v}\text{e}\text{n}\text{e}\text{s}\text{s}\right) \times \text{e}\text{v}\text{e}\text{n}\text{n}\text{e}\text{s}\text{s}$$

which indicates that the parity of aquaculture captures its inclusiveness and evenness as two dimensions of the balance of global aquaculture. When aquaculture is all inclusive (i.e. 100 percent popularity), parity will be the same as evenness. Therefore, parity can be viewed as an extended measure of evenness that gauges the balance of aquaculture production among existing as well as potential aquaculture countries, while indicator 7 only measures the balance among existing aquaculture countries.

2.1.8 Indicators 9 and 10: intra-regional parity versus inter-regional parity

According to equations (2) and (9), the global parity can be decomposed into two components:

Global parity = intra-regional parity × inter-regional parity, (12)

where the intra-regional parity is the intra-regional diversity normalized by the average number of countries in a region, i.e.,

Intra-regional parity $=\frac{\text{W}\text{G}\text{E}\text{N}\text{C}}{\stackrel{-}{N}/5}$, (13)

while the inter-regional parity is the inter-regional diversity normalized by the number of regions, i.e.,

Inter-regional parity $=\frac{\text{E}\text{N}\text{C}\text{G}}{5}$. (14)

As inter-regional diversity (ENCG) ranges between 1 and 5, inter-regional parity ranges from 20 percent to 100 percent. Then according to Eq. (12), intra-regional parity ranges from parity to 5 times of parity.

2.1.9 Summary

Popularity (indicator #6), parity (#8), intra-regional parity (#9), and inter-regional parity (#10) are derivative indicators (by normalization) from abundance (#2), diversity (#3), intra-regional diversity (#4), and inter-regional diversity (#5), respectively. While the two sets of indicators are essentially equivalent for a country group at a specific time, they may have different implications when comparing different country groups or the same group over time.

For example, suppose that there were 5 aquaculture countries among 20 countries in subregion A, while subregion B had 3 aquaculture countries among 10 countries. Then subregion A would have more abundant aquaculture countries than subregion B (i.e. 5 versus 3), whereas aquaculture in subregion B is more inclusive (i.e. 30 percent popularity) than subregion A (only 25 percent). Suppose that the number of countries in a trade bloc increased from 10 to 15, with the diversity of aquaculture countries rising from 5 ENC to 6 ENC. Under this situation, adding five new members would increase the diversity of aquaculture countries in the trade bloc yet reduce the parity from 50 percent to 40 percent.

These examples indicate that popularity and parity are more meaningful indicators for comparison of aquaculture imbalance across country groups or over time. Therefore, we will focus on them in the following discussion but present the results of all indicators in supplementary materials.

2.2 Data

2.2.1 Data sources and curation

Data on aquaculture and capture fisheries production are from the Food and Agriculture Organization of the United Nations (FAO) fishery and aquaculture production statistics (1950–2020)⁹, while data on terrestrial meat production are from the FAOSTAT data on crops and livestock products (1961–2021)²⁵. Our study covers the period 1970–2020.

The two FAO databases categorize reporting entities as countries, including non-sovereign territories. We combine mainland Tanzania and Zanzibar (two separate reporting entities in the fisheries and aquaculture statistics) into a single entity (i.e. the United Republic of Tanzania) to be consistent with the FAOSTAT data on terrestrial meat production. For all other reporting entities, we follow the classifications provided in the FAO databases. For a few countries with missing data on terrestrial meat production in year 2019 and/or 2020, we fill in the missing data by previous year data or estimate. The number of countries in the final dataset is treated as the number of all countries, i.e. the normalizing factor $\stackrel{-}{N}$ used to calculate popularity and parity.

2.2.2 Country grouping

We examine a total of 85 country groups, including five categories: (i) world as well as the rest of world (ROW), excluding China; (ii) 27 geographic groups; (iii) 19 economic groups; (iv) 17 development groups; and (v) 20 resource groups. The geographic groups include five regions and 22 subregions; the grouping mostly follows the United Nations M49 standard. The economic groups are mostly trade blocs or economic unions (e.g. NAFTA, ASEAN, and the EU) as well as international organizations (e.g. OECD). The development groups include five customary development groups (e.g. Least Development Countries or Small Island Developing States), four income groups according to the World Bank classification, and four quartile groups categorized by the UNDP Human Development Index (HDI), and four quartile groups by urban ratio (i.e. the ratio of urban population in a country’s total population). The 20 resource groups include four quartile groups categorized by each of the five resources: population, land area, coastline length, inland water surface, and renewable freshwater water resources. A summary of country grouping is presented in Supplementary Table 1.

2.2.3 Species grouping

We examine a total of 43 species groups, including (i) all species; (ii) algae and two algae subgroups; (iii) aquatic animals; (iv) finfish and 19 finfish subgroups; (v) molluscs and six molluscs subgroups; (vi) crustaceans and five crustacean subgroups; and (vii) miscellaneous aquatic animals and animal products (MAA) and four MAA subgroups. These species groups or subgroups are primarily based on the International Standard Statistical Classification of Aquatic Animals and Plants (ISSCAAP) with a few subgroups based on WAPI species grouping under the FAO World Aquaculture Performance Indicators²⁶. A summary of species grouping is presented in Supplementary Table 2.

3.1 Global aquaculture popularity and parity

3.1.1 1970–2020: increased popularity with declined parity (both inter- and intra-regional)

In 1970, aquaculture played a small role in global food production, with 3.7 million tonnes of world aquaculture production accounting for only 5.5 percent of total fisheries (including aquaculture and capture fisheries) production. With only 62 countries adopting this novel food production system, the popularity of aquaculture was 31.2 percent of all 199 countries at that time (Fig. 1a). Additionally, the 3.7 million tonnes of world production was unevenly distributed among the 62 countries (Fig. 2a) and across the five regions (Fig. 3a), resulting in 5.3 percent global parity of aquaculture (10.5 ENC among all 199 countries) and 38.2 percent inter-regional parity (1.91 ENCG among all five regions) (Fig. 1a and 1b).

Five decades of rapid growth in aquaculture has made it the primary source of total fisheries production. In 2020, the 123 million tonnes of world aquaculture production accounted for 57.3 percent of total fisheries production, and the popularity of aquaculture reached 84.5 percent (Fig. 1a), with aquaculture being practiced in 196 countries. However, the parity of aquaculture has dropped to 2.8 percent (6.5 ENC among all 232 countries), with declines in both intra- and inter-regional parities (Fig. 1a and 1b) due to increasingly imbalanced distribution of aquaculture production within and between regions (Fig. 2a–2c; Fig. 3a–3c).

3.1.2 New millennium (2000–2020): increased global parity despite declined inter-regional parity

The inter-regional parity of aquaculture declined slightly between 2000 and 2020 (Fig. 1b), reflecting a further increase of Asia’s dominance in world aquaculture (Fig. 3b and 3c). The global parity, however, increased in the new millennium thanks to a higher intra-regional parity (Fig. 1a and 1b), which was primarily driven by an increase in the parity of aquaculture within Asia, where China yielded its production share to other Asian countries (Fig. 2b and 2c). More recently, there was a sign that the inter-regional parity was turning into an upward trend, increasing slightly from 29.1 percent in 2015 to 29.4 percent in 2020 (Fig. 1b).

The improved aquaculture parity in the new millennium primarily reflects decelerating aquaculture growth in Asia from 6 percent (per year) during 2010–2015 to 3.3 percent during 2015–2020, particularly in China (from 4.4 percent to 3.5 percent). For the other four regions, while aquaculture growth has accelerated in the Americas (from 5.4 percent to 6 percent) and Oceania (from 0.1 percent to 3.1 percent), the growth rate has declined in Europe (from 3.2 percent to 2 percent) and Africa (from 6.8 percent to 3.6 percent, or 4.9 percent during 2015–2019 prior to the COVID pandemics). The 6 percent growth in the Americas (the best performer recently) was not even half of the 14.6 percent annual aquaculture growth in Asia during 1990–1995.

3.1.3 Lower global parity of aquaculture (both intra- and inter-regional) than other food production systems

Capture fisheries has been a traditional food production system with nearly 100 percent popularity. In 2020, among 232 food producing countries covered in our study, only one country (Luxemburg) had no capture fisheries production. The parity of capture fisheries (global as well as intra- and inter-regional) has also been much higher than that of aquaculture (Fig. 4a–4c), reflecting more even distribution of capture fisheries production among countries (Fig. 2d–2f) and regions (Fig. 3d–3f). While aquaculture parity declined from 5.3 percent to 2.8 percent during 1970–2020, the parity of capture fisheries increased from 12.6 percent to 17.6 percent. The negative correlation between the two trends was nevertheless moderate (r = −0.39), and both of them moved upward in the new millennium (Fig. 4a). The correlation between their intra-regional parities was also moderate negative, whereas there was a moderate positive correlation between their inter-regional parities (Fig. 4d).

In 1970, the global, intra-regional, and inter-regional parities of total fisheries production nearly coincided with those of capture fisheries, which accounted for 95 percent of total fisheries production at the time. Yet the two sets of parities went on diverging paths (Fig. 4a–4c), as capture fisheries continued losing its production share to faster growing yet more imbalanced aquaculture. In the new millennium when the aquaculture share nearly doubled from 31 percent in 2000 to 57 percent in 2020, the parity of total fisheries production declined from 10.3 percent to 7.5 percent, despite increased parities in both aquaculture and capture fisheries. In contrast, the parity of terrestrial meat production has increased from 12.1 percent to 13.3 percent in the new millennium (Fig. 4a).

While not obvious from a visual comparison of production distribution (Fig. 2g versus 2j), the parity of terrestrial meat production in 1970 (15.1 percent) was higher than total fisheries production as well as its two components (Fig. 4a). The parity declined to 13.3 percent in 2020, which was below that of capture fisheries, yet still higher than aquaculture and total fisheries production. The decline was primarily due to a drop in the intra-regional parity of terrestrial meat production from 20.7 percent to 18.2 percent (Fig. 4b), while the inter-regional parity remained relatively unchanged and at the highest level (~ 73 percent) compared to aquaculture, capture fisheries, and total fisheries production (Fig. 4c).

Even though the parity of terrestrial meat production has been much higher than that of aquaculture, the two trends moved in tandem during 1970–2020 (Fig. 4a) with a high correlation (r = 0.93) between their intra-regional parities and a moderate one (r = 0.43) between their inter-regional parities (Fig. 4d).

3.2 Aquaculture popularity and parity by country group

3.2.1 High aquaculture popularity in most country groups

The popularity of aquaculture has increased during 1970–2020 in all 85 country groups examined here (Supplementary Table 3, column IX). In 1970, aquaculture popularity was above 90 percent in only three country groups, while it was below 30 percent in 37 groups, including eight country groups with zero popularity (Supplementary Table 3, column VI). In 2020, aquaculture popularity was higher than 40 percent in all the 85 country groups, and it was higher than 90 percent in 54 groups, including 28 country groups with 100 percent popularity (Supplementary Table 3, column VIII).

In 2020, among the 232 food producing countries covered in our study, 35 countries had no aquaculture production (Supplementary Table 4). These 35 countries spread across Africa (10 countries), the Americas (13), Asia (4), Europe (3), and Oceania (5); more than half (24) of them are island economies; and 15 countries are Small Island Developing States (SIDS). These 35 countries, representing 15 percent of all 232 countries notwithstanding, accounted for only 1.9 percent of global capture fisheries and 0.4 percent of global meat production. Among them, Mauritania and Yemen were the only two countries with relatively large (> 100 000 tonnes) capture fisheries as well as terrestrial meat production.

3.2.2 Increased aquaculture parity in most country groups

The parity of global aquaculture has largely mimicked the trend in Asia (Fig. 1c), the largest aquaculture region that accounts for over 90 percent of world production (Fig. 3c). Besides Asia, Europe was another region that contributed to the decline in global aquaculture parity between 1970 and 2020, whereas aquaculture parity has increased in the other three regions (Fig. 1c–1g). Indeed, despite the significant drop in global parity, aquaculture parity has increased during 1970–2020 in a majority (58) of all 85 country groups examined here, including (i) 18 of the 27 geographic groups, (ii) 14 of the 19 economic groups, (iii) 12 of the 17 development groups, and (iv) 14 of the 20 resource groups (Supplementary Table 3, column XIV).

In the new millennium (2000–2020), aquaculture parity has increased in 50 country groups, including, among others, (i) three regions (Africa, the Americas, and Asia); (ii) all six subregions and four trade blocs in Africa; (iii) all three trade blocs in Europe (despite a declined parity in Europe as a whole); (iv) all five customary development groups (Developed Regions, Developing Regions, Least Developed Countries, Landlocked Developing Countries, and SIDS); and (v) five most resource-rich quartile groups in terms of population, land area, coastline length, inland water surface area, or renewable water resources (Supplementary Table 3, column XV).

3.2.3 More balanced aquaculture growth at the regional level than other food production systems

Global aquaculture development between 1970 and 2020 was an imbalanced growth with a statistically significant (p < 0.05) negative correlation between the time series of production and parity during 1970–2020 (r = −0.74), which means that the expansion has resulted in a lowered parity. However, aquaculture expansion in the 85 country groups has been largely a balanced growth, with a significant positive correlation between the time series of aquaculture production and parity in 42 country groups (including three regions and nine subregions), as opposed to a significant negative correlation in only 21 groups, including two regions and four subregions (Supplementary Table 5, column II).

In contrast, 34 country groups have experienced a significant negative correlation between the parity and production of capture fisheries, as opposed to a significant positive correlation in only 25 groups (Supplementary Table 5, column III). The growth in terrestrial meat production was even more imbalanced, with a significant negative correlation between the time series of production and parity in 53 country groups versus a significant positive correlation in only 25 groups (Supplementary Table 5, column V).

In the new millennium (2000–2020), global aquaculture expansion has been a balanced growth with a significant positive correlation between the time series of production and parity during the period (r = 0.86). Aquaculture growth in other country groups was still largely balanced, yet a significant negative correlation between the time series of aquaculture production and parity has been observed in 27 country groups (Supplementary Table 5, column VI), including one region (Europe) as well as six relatively large subregions (Eastern Asia, South-eastern Asia, Western Asia, Northern America, Northern Europe, and Eastern Europe) that accounted for 84 percent of world aquaculture production in 2020.

3.2.4 Lower parity in aquaculture than other food production systems in most country groups

In 2020, aquaculture parity was lower than both capture fisheries and terrestrial meat production (i.e. double negative parity gaps) in 63 of all 85 country groups (Supplementary Fig. 2; Supplementary Table 6, columns XII and XIII), including 17 of the 27 geographic groups (Fig. 5). Asia (the largest aquaculture region) belonged to this category; so were its five subregions, including Central Asia that had the largest negative parity gap between aquaculture and terrestrial meat production. Europe also had double negative parity gaps, even though its aquaculture parity was the highest among the five regions. Yet Southern Europe had double positive parity gaps.

Africa had relatively large double negative parity gaps, since its aquaculture parity was the lowest among all the five regions while the parities of its capture fisheries and terrestrial meat production were the highest. Large double negative parity gaps also occurred in most African subregions, except for Southern Africa that had double positive parity gaps (Fig. 5; Supplementary Table 6, columns XII and XIII).

While aquaculture parity in the Americas was slightly lower than capture fisheries, it was higher than terrestrial meat production. Indeed, most of the American subregions had an aquaculture parity similar to or greater than the other two parities, except for the Caribbean that had relatively large double negative gaps (Fig. 5; Supplementary Table 6, columns XII and XIII). Similar to the Americas, Oceania’s aquaculture parity was lower than capture fisheries yet higher than terrestrial meat production, yet the region’s negative parity gap between aquaculture and capture fisheries was much larger. This reflected the situation in Pacific Islands, whereas the subregion of Australia and New Zealand had double positive parity gaps (Fig. 5; Supplementary Table 6, columns XII and XIII).

3.2.5 High correlations between aquaculture parity and other food production systems

A country group with a relatively high parity in capture fisheries tends to have a relatively high aquaculture parity; so does a country group with a relatively high parity in terrestrial meat production. In 2020, among all 85 country groups examined, the correlation between aquaculture parity and that of capture fisheries was 0.56, while that between aquaculture and terrestrial meat production was 0.57. The two correlations were also positive among the geographic, economic, development, or resource groups, yet their magnitude varied (Supplementary Fig. 2).

Both correlations were also significant positive among the 27 geographic groups (Fig. 5). So were they among the six Asian geo-groups (Asia and its five subregions) as well as the three Oceania geo-groups. Yet neither of the two correlations was statistically significant among the seven African geo-groups or the five European geo-groups. For the six American geo-groups, the parity correlation was significant positive between aquaculture and terrestrial meat production (Fig. 5b), but not between aquaculture and capture fisheries because of a much lower aquaculture parity than capture fisheries in the Caribbean (Fig. 5a).

3.3 Aquaculture popularity and parity by species group

We examine the aquaculture popularity and parity of a total of 43 species groups (Supplementary Table 2); each of them had a global aquaculture production exceeding 100 000 tonnes in 2020. The results are summarized in Supplementary Tables 7 and 8.

3.3.1 Increased yet still low popularity of aquaculture for most species groups

Aquaculture parity has increased between 1970 and 2020 for all 43 species groups examined here (Supplementary Table 7, column IX). However, the relatively high overall popularity of aquaculture (84 percent in 2020) was primarily thanks to the popularity of finfish farming (82 percent), whereas the aquaculture popularity of molluscs (27 percent), crustaceans (34 percent), and MAA (11 percent) were below half of their popularities in capture fisheries (Fig. 6c). While higher than capture fisheries, the popularity of algae farming was only 21 percent.

In 2020, tilapias were cultivated in 124 countries (53 percent popularity), yet it was the only species subgroup with an aquaculture popularity higher than 50 percent (Fig. 7a; Supplementary Table 8, column VIII). Other subgroups with a relatively high aquaculture popularity (> 20 percent in 2020) included carps (41 percent), catfishes (39 percent), salmon and trout (35 percent), marine shrimps (27 percent), and marine perch-like fishes (20 percent).

3.3.2 Diverse parity trends among species groups

Between 1970 and 2020, while aquaculture parity for all species as a whole has declined, the parity trends for the other 42 species groups almost split, with 22 groups experiencing an increase in aquaculture parity while 20 groups experiencing a decrease (Supplementary Table 7, column XIV). However, all five major species groups have had a downward parity trend, whereas the 22 groups with an upward trend were all species subgroups. In the new millennium, 19 species groups (including all species as a whole, aquatic animals, finfish, and algae) have experienced an increase in aquaculture parity between 2000 and 2020, while aquaculture parity has declined for the other 24 species groups, including three of the five major species groups (crustaceans, molluscs, and MAA) (Supplementary Table 7, column XV).

The overall aquaculture parity declined between 1970 and 2000 while increased between 2000 and 2020 (Fig. 1a). A similar U-shape trend occurred for another 11 species groups (e.g. aquatic animals, finfish, algae, carps, and brown seaweeds), while 17 species groups (e.g. crustaceans, MAA, marine perch-like fishes, freshwater perch-like fishes, red seaweeds, mussels, scallops, marine shrimps, and crayfishes) had an inverted U-shape trend (Supplementary Table 7, column XVII). The other 14 species groups had a more straightforward parity trend during 1970–2020, including seven groups (e.g. tilapias and catfishes) with a straight-up trend and seven groups (e.g. molluscs, oysters, clams, salmon and trout, and milkfish) with a straight-down trend (Supplementary Table 7, column XVII).

3.3.3 Low aquaculture parity for all species groups

In 2020, aquaculture parity varied among the 43 species groups from 0.4 percent (for freshwater crabs) to 4.7 percent (for tilapias), with the median parity at 1.03 percent (Supplementary Table 8, column X). The parity of mollusc was at the median; those of finfish (3.7 percent), crustaceans (2.5 percent), and algae (1.3 percent) were above, while that of MAA (0.6 percent) was below.

Tilapias, salmon and trout, and marine shrimps (i.e. three largest aquaculture commodities in international trade) were the only three species subgroups with an aquaculture parity higher than 3.5 percent (Fig. 7a). Mussels, catfishes, and marine perch-like fishes also had a relatively high aquaculture parity (> 2.5 percent).

In 2020, there was a strong positive correlation between aquaculture popularity and parity among the 43 species groups (r = 0.74), and tilapias had the highest aquaculture popularity and parity among the 36 species subgroups. However, the parity of carps, the largest and the second most popular species subgroup notwithstanding, was only 1.5 percent, while diadromous perch-like fishes as well as characins had a parity around 2 percent despite their less than 10 percent popularity (Fig. 7a).

In 2020, inter-regional aquaculture parity varied among the 43 species groups between 20 percent (i.e. the lower bound) and 63.3 percent, with the median at only 22.1 percent (Supplementary Table 8, column XII). Six species subgroups (Asian swamp eel, gouramies, milkfish, freshwater crabs, marine crabs, and turtles) had an inter-regional parity equal or approximate to the lower bound 20 percent, as they were cultivated entirely or almost entirely in Asia. Mussels (63.3 percent) and salmon and trout (56.4 percent) were the only two species subgroups with an inter-regional parity above 50 percent, while tilapias, characins, marine perch-like fishes, and marine shrimps also had a relatively high (> 30 percent) inter-regional parity (Fig. 7b).

Among the five major species groups, finfish was the only one with an inter-regional parity above 30 percent, while those of algae and MAA were around 21 percent (Fig. 6e). Finfish also had a relatively high (above 10 percent) intra-regional parity, which ranged between 2.2 percent and 11.6 percent (median at 4.6 percent) among the 43 species groups (Supplementary Table 8, column XI). Catfishes had the highest intra-regional parity, whereas marine shrimps, diadromous perch-like species, and tilapias were the other three species groups with an intra-regional parity higher than 10 percent (Fig. 7b).

In 2020, the global parities of all five major species groups were much lower than their counterparts in capture fisheries (Fig. 6d), even for algae whose aquaculture popularity was higher than that of capture fisheries (Fig. 6c). Their inter-regional and intra-regional parities of aquaculture were also generally lower than capture fisheries, except that the intra-regional aquaculture parity of algae was slightly higher than capture fisheries (Fig. 6f).

From a novel food production system adopted in around 60 countries in 1970, aquaculture has developed into a global business undertaken in nearly 200 countries in 2020. However, the “globalization” is primarily thanks to finfish farming, which is practiced in over 80 percent of countries, whereas aquaculture popularity is less than 50 percent for nearly all 43 aquatic species groups examined here, including crustaceans and molluscs whose aquaculture popularities are less than half of their popularities in capture fisheries. Therefore, while the overall popularity of aquaculture appears to have reached a high plateau (Fig. 1), there is still ample potential for the popularization of minor species groups, particularly for eco-friendly ones such as algae and molluscs, which are receiving increasing attention^27–29 .

Despite the increased popularity, the global aquaculture expansion (from less than 4 million tonnes in 1970 to over 120 million tonnes in 2020) has reduced the sector’s parity from an already low level to below 3 percent. This extraordinary, inclusive, yet imbalanced development primarily reflects faster growth in some aquaculture forerunners (mostly in Asia) creating more disparity within Asia and between Asia and other regions, while aquaculture production has become more balanced in most regions and subregions as well as most economic, development, and resource groups examined here. This means that aquaculture expansion has been largely a balanced growth among countries with similar geolocations, resource endowments or socioeconomic status, with young aquaculture sectors catching up with more developed ones. Such catching up has also occurred within Asia in the new millennium (2000–2020), and between Asia and other regions more recently (2015–2020), resulting in a more balanced global aquaculture.

However, aquaculture is still the least diverse food production system in terms of national producers. In 2020, global aquaculture production was contributed by 6.5 effective number of countries (ENC) as compared to ~ 40 ENC for capture fisheries and ~ 30 ENC for terrestrial meat production. The parity of aquaculture production was lower than both capture fisheries and terrestrial meat production in nearly three fourths of the 85 country groups examined here, including three regions (Africa, Asia and Europe), and aquaculture parity was less than that of capture fisheries in all five regions.

A country group with a relatively low aquaculture parity also tends to have relatively low parities in other food production systems. This indicates that the uneven distribution of aquaculture production partly reflects discrepancies in countries’ characteristics (e.g. geographic location and climate, resource endowments, demographics, socioeconomic conditions, and development status), which tend to result in imbalances in other food production systems as well. For example, in 2020, most (49) of the 53 countries that had a relatively large share in global aquaculture production also had relatively large shares in both capture fisheries and terrestrial meat production, yet none of them had relatively small shares in both (Fig. 8a). Most (over 40) of the 49 major food producers are resource-rich countries (Supplementary Table 9, column VIII), and their generally large land areas make them a most prominent group in the map (Fig. 8a; group 8). In contrast, the group of countries with relatively small shares in all three food production systems are barely visible in the map despite being the largest group that comprises 75 countries (Fig. 8a; group 1). These minor food producers generally have relatively small resource endowments and populations, and most of them are small island economies (Supplementary Table 9, column II).

However, the much higher imbalance in aquaculture cannot be fully attributed to discrepancies in countries’ resource endowments, including population. For example, a large number (44) of generally resource-rich countries had relatively large shares in capture fisheries and terrestrial meat production yet relatively small shares in aquaculture (Supplementary Table 9, column V). These countries are another most prominent group in the map (Fig. 8a; group 4), covering most of the African continent and including three of the top 10 largest countries in terms of land area (Argentina, Kazakhstan, and Algeria) and three of the top 20 most populated countries (Ethiopia, the Democratic Republic of Congo, and Germany).

The highly uneven geographic distribution of aquaculture production has raised concerns over the sector’s widely expected role as the primary source of aquatic foods to address the food security and nutrition needs of a growing world population¹². As an emerging production system, aquaculture could add resilience to the global food system by increasing the diversity of food production sources¹³. Yet faster growth in aquaculture as a more imbalanced fisheries subsector, compared to capture fisheries, has continually pressed down the parity of total fisheries production, even in the new millennium when the parity has increased in both subsectors. This could weaken the resilience of the global food system against various environmental, biological, socioeconomic, and geopolitical risks, such as climate change, natural disasters, disease outbreaks (both animal and human), economic crises, trade disputes, political instability, and armed conflicts^10,30.

The upward trend in global aquaculture parity since the turn of the century (as well as growing inter-regional parity since the mid-2010s) seems to be a sign that the emerging sector has started correcting its imbalance in the process of maturation. The magnitude of the improvement was nevertheless minimal. More importantly, the correction was a passive catching-up primarily due to aquaculture growth losing momentum in Asia, rather than accelerating growth in other regions. Most notably, aquaculture parity in Africa, being the lowest among the five regions notwithstanding, has declined recently (Fig. 1f). According to the projection of Chan et al.³¹, the uneven distribution of aquaculture production in Africa is expected to persist till 2050 under a business-as-usual scenario.

As a side effect of the emerging sector’s extraordinary growth driven primarily by a few forerunners, high disparity in global aquaculture should be a cause for concern, but not pessimism. On the contrary, the unevenness indicates a large untapped potential for further aquaculture growth³². In 2020, there were 147 countries whose shares in world aquaculture production were lower than their shares in both capture fisheries and terrestrial meat production (Supplementary Table 10); 44 countries among them belong to group 4 (Fig. 8a), while the others spread across groups 1, 2, 3, and 8. Raising aquaculture production in each of these 147 countries to a level on par with either its capture fisheries or terrestrial meat production share (whichever is lower) could expand aquaculture production by 1.6 times in Africa, 2.4 times in the Americas, 2.5 times in Europe, and 2.9 times in Oceania, adding a total of 26 million tonnes to global aquaculture production (Supplementary Table 10). Even discounted by half, considering that aquaculture expansion may compete for resources and markets with other food production systems, the potential would still be substantial.

Indeed, aquaculture success is not necessarily driven by abundant resources. For example, two thirds of aquaculture production in Africa came from a single country (i.e. Egypt), which was endowed with only ~ 1 percent of renewable freshwater resources in Africa, ~ 3 percent of the region’s land area, and ~ 8 percent of its population³³. Aquaculture production in the country mostly relied on imported aquafeed ingredients and catered the domestic market³⁴. With more than 10 times of Egypt’s population, not mentioning even more abundant land and water resources, Africa could boost its aquaculture production (only 2.4 million tonnes in 2020) beyond 15 million tonnes (i.e. at least 10 times of Egypt’ ~1.5 million tonnes of annual aquaculture production) by replicating the country’s aquaculture performance regionwide.

Turning such potentials into reality requires a deeper look beyond the performance of global aquaculture as a whole for better recognition and understanding of imbalances in aquaculture. For example, while aquaculture’s contribution to global fisheries production, including algae, has exceeded the 50-percent mark since the early 2010s³⁵, reaching nearly 60 percent in 2020, it is still a smaller fisheries subsector, compared to capture fisheries, in nearly 80 percent of countries, and its contribution is less than 25 percent in two thirds of countries that control most of global land and water resources (Fig. 8b). Recognizing such gaps can help the policy and aquaculture communities better appreciate various constraints faced by aquaculture (e.g. unfavourable public perceptions, stringent regulatory scrutiny, and inadequate financial and development supports) and design proper development strategies to unlock aquaculture growth potential.

In conclusion, aquaculture popularity and parity could be mainstreamed as performance indicators in policymaking and sector management to facilitate more inclusive aquaculture development, enhance the resilience of the global food system, and unlock potential for further aquaculture growth. We can only manage what you can measure. The indicator system developed here enables systematic assessment and monitoring the distribution of aquaculture production among countries and regions. Popularity and parity, as a novel extension of traditional diversity measures, can be widely applied in sector assessment and monitoring for any sector or at different levels, such as monitoring the geographic distribution of food production at the subnational level³⁶. Space limit does not allow a thorough analysis of all information generated by our assessment, including results related to other food production systems (capture fisheries and terrestrial meat production), which are used here as benchmarks for the assessment of aquaculture performance. Yet we document the comprehensive results in the supplementary materials (Supplementary Table 11.1–11.5) to facilitate further study.

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Popularity and parity: towards more inclusive and balanced aquaculture

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Abstract

Figures

1. Introduction

2. Method and data

2.1 A 10-indicator system for assessment of production distribution among countries and regions

2.1.1 Indicator 1: total production as a basic measure of overall performance

2.1.2 Indicator 2: total number of aquaculture countries (n) as a measure of abundance

2.1.3 Indicator 3: effective number of countries (ENC) as a measure of diversity

2.1.4 Indicators 4 and 5: intra-regional diversity versus inter-regional diversity

2.1.5 Indicator 6: popularity

2.1.6 Indicator 7: evenness

2.1.7 Indicator 8: parity

2.1.8 Indicators 9 and 10: intra-regional parity versus inter-regional parity

2.1.9 Summary

2.2 Data

2.2.1 Data sources and curation

2.2.2 Country grouping

2.2.3 Species grouping

3. Results

3.1 Global aquaculture popularity and parity

3.1.1 1970–2020: increased popularity with declined parity (both inter- and intra-regional)

3.1.2 New millennium (2000–2020): increased global parity despite declined inter-regional parity

3.1.3 Lower global parity of aquaculture (both intra- and inter-regional) than other food production systems

3.2 Aquaculture popularity and parity by country group

3.2.1 High aquaculture popularity in most country groups

3.2.2 Increased aquaculture parity in most country groups

3.2.3 More balanced aquaculture growth at the regional level than other food production systems

3.2.4 Lower parity in aquaculture than other food production systems in most country groups

3.2.5 High correlations between aquaculture parity and other food production systems

3.3 Aquaculture popularity and parity by species group

3.3.1 Increased yet still low popularity of aquaculture for most species groups

3.3.2 Diverse parity trends among species groups

3.3.3 Low aquaculture parity for all species groups

4. Discussion

References

Additional Declarations

Supplementary Files

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