A network analysis of global cephalopod trade

Trends in cephalopods trade

Since 2000, trade in fresh octopus has been constantly dominated by the flow from China to Korea, followed by Vietnam to Japan, Portugal to Spain and Spain to Italy. However, there has been a marked decrease in the traded volume and monetary value over time, with a 50% reduction in the top 5 traders (Tables S3–S5).

Over the last 20 years, fresh octopus exports have been strongly dominated by China, followed by Spain, Vietnam, Portugal, and France, and recently by Morocco and Thailand (Table S3). While Vietnam was the most important exporter in the first period (2000–2005), it was not within the top 5 traders in the last 5 years. Imports have been dominated by Korea, Italy, and Portugal, with no notable changes in the whole period (Table S4). Regarding trade of processed octopus, the largest transactions have been performed from Morocco to Spain, Morocco to Japan, Mauritania to Japan (and more recently also to Spain) and China to Korea (Table S5). Since 2000, exports of processed products have been dominated by Morocco, Mauritania, China, Spain, and Vietnam (Table S3), while imports have been led by Japan, Spain, Italy, Korea, and the United States (Table S4).

Trade in volume of fresh cuttlefish and squid includes fewer clear relationships over time, such as transactions from Malaysia to Singapore (2000–2004 and 2005–2009); from Myanmar to Thailand (2005–2009 and 2015–2019); and from Yemen to Vietnam (2010–2015) (Tables S6-S8). For the first 5 years, exports of fresh commodities were dominated by Vietnam. However, since 2005, India, Spain and France have increased their exports in both monetary value and volume, displacing Vietnam from the top rank (Table S6). The main importing traders were Spain and Italy. Although China was important in the first decade, it was replaced by Vietnam in the last decade (Table S7). The trade of elaborated cuttlefish and squid products was dominated by monetary value flow from Thailand to Japan and from Malvinas/Falkland Islands to Spain in the first decade, while in the last decade the flow from China to other traders (Japan, the USA, and Thailand) gained relevance. However, the volume follows a different pattern, with flow from the Malvinas/Falkland Islands to Spain and from Korea to China in the first decade, while in the last decade, flows from Peru to China and from China to Thailand were important (Table S8). A disparity exists between the top five traders in terms of flow of monetary value and volume in the first 15 years; but in the last 5 years the top positions are constantly represented by, China, Peru, India, and Spain. Italy, Japan, China, and the USA are important importers in terms of monetary value and volume, although in the last decade Thailand has increased its importance, replacing the USA in the top 5 in the last 5 years (Table S7).

The CGTN involved 220 traders (countries or territories) from around the world with exports greater than or equal to 500 kg between 2000 and 2019 (Fig. 3). The remaining 32 traders either did not report exports or their exports were below 500 kg. The most important cluster of traders was composed by 8 countries that dominate the cephalopod global markets in Asia (China, India, Republic of Korea, Thailand, Vietnam), Europe (the Netherlands, Spain) and the USA. The second and third most relevant clusters were composed of 8 and 12 traders, respectively. These two clusters involve 9 developed countries (Belgium, Canada, Denmark, France, Germany, Italy, Japan, United Kingdom and Portugal) and 11 developing countries (Morocco, Malaysia, UAE, Senegal, South Africa, Peru, Indonesia, Philippines, Argentina, Chile and New Zealand). Some of these traders have the most productive cephalopod fisheries in the world (e.g., Patagonian shortfin squid in the Southwest Atlantic Ocean and Patagonian squid in the Southeastern Pacific Ocean).

Octopus trade network

Live, fresh, or chilled octopus

The normalised strength (Fig. 4) revealed the importance of China and Republic of Korea in the trade of fresh octopus in monetary value, with high importance of flows between these two traders over time (Supplementary Fig. S1). Other relevant traders over time were Spain, Portugal and Italy, in Europe; and Vietnam and Japan, in Asia from 2000 to 2004 (Supplementary Fig. S1). The network based in volume showed similar results.

The Betweenness identified important actors facilitating flow through the network. For fresh octopus, the most relevant traders in the last two decades were Spain, France, and Italy, followed by Thailand, Portugal and the USA. Again, no major differences exist between the monetary value and volume networks. However, the ranking of traders changed over time, with Italy replacing Spain in the first place during the period 2005–2009, and then Spain consolidating again in the first place in the following periods. Also, in the last 20 years there were many changes in Asia, with Vietnam losing and Korea gaining prominence over time (Supplementary Fig. S2).

In a global trade network, there are countries that are essential to the network structure because they are connected to other countries critical to the network and those critical countries, in turn, have no other significant connections. PageRank is a centrality measure that identifies these important countries, resulting from an iterative algorithm that assigns higher values to countries with a greater number of import connections with other countries that move large quantities of goods or money³³. In the last 20 years, Italy, Germany France and Spain have occupied those central positions in the global trade network of live, fresh or chilled octopus. Their dominance has not changed over the four 5-year periods analysed (Fig. 5).

Elaborated octopus

The normalised strength revealed a diversified trade network for elaborated octopus products. This network has remained relatively stable over the last 20 years, with some exceptions. In the 2000s, there was an intense flow of exports from North Africa (i.e., Morocco and Mauritania) to Japan, although the most important flow was from Morocco to Spain. In the 2010s, Mauritania changed its preferential partner and exported large quantities of elaborated octopus to Spain, with the latter gaining dominance. In this last decade, flows from China and Vietnam to the Republic of Korea also became important. Other relevant actors were distributed globally (e.g., Italy, Portugal, Senegal, the USA). However, the most important routes showed a common pattern: the origin was in developing countries or territories (that emerged as producers) while developed countries showed a high and stable consumer demand (Supplementary Fig. S3). The network based on volume was highly similar to the monetary value network. However, Italy, China, Korea, Vietnam, and the USA reduced their importance compared to the top-ranked traders (i.e., Spain, Japan, and Morocco). The most important routes of the volume network were from China to Korea; Morocco to Spain; Morocco and Mauritania to Japan and Vietnam to Korea.

The Betweenness measure highlighted the role of Spain as a facilitating actor in the trade network of elaborated octopus, followed by Italy, China, and the USA. These countries have maintained their importance as structurers of the world trade network in elaborated octopus over the past 20 years. Similarly, the routes from Italy to Spain, and from Spain to China and the USA emerged as relevant in the network structure, with a special mention to the route between Japan and China in the last 5-year period (Supplementary Fig. S4). There are no major differences between the most central traders in this network and the volume-based one.

PageRank revealed the importance of Spain and Italy as leading traders in the elaborated octopus market. These two countries concentrated a large number of import relationships, which also concentrated a large monetary and volume flow. This importance has been maintained over time. Other reference actors were Greece, Japan, the USA and Portugal, in the first decade; and the USA, Portugal, Greece and Korea in the second decade. Note how in the second decade, Greece and Japan lost relevance, while Northern European countries and the Republic of Korea gained relevance (Supplementary Fig. S5).

Squid and cuttlefish trade network

Live, fresh, or chilled squid and cuttlefish

The normalised strength revealed the importance of Spain, France, Italy, and India in the trade network of fresh squid and cuttlefish products, especially the route between east Asia and Spain (Fig. 6). The volume-based network is highly similar to the monetary value network. Over the four 5-year periods analysed, Vietnam and Japan have gradually lost relative importance in the network (Supplementary Fig. S6).

For fresh squid and cuttlefish, Betweenness identified Spain as the most important structurer of the network, in both monetary value and volume, over the time. Europe emerged as a major region structuring the global trade network. While in Asia, the exchange of countries with higher betweenness over time evidences the strong struggle for control of trade in the region and the more fragile sub-networks. In the monetary network, in the 2000s the bridge between the United Kingdom and Korea stood out, while in the 2010s the Europe-Asia bridge was established between Spain and India. In the volume-based network, it is noteworthy that in the 2010s there were many critical routes for the stability of the network, even in the Europe–Asia connection. Note, for example how the link between Netherlands and Myanmar stand out (Supplementary Fig. S7).

PageRank revealed the importance of Italy, Spain, Germany and France as leading traders in the fresh squid and cuttlefish market. In the last 20 years, Europe concentrated the largest number of import relationships, which also concentrated a large monetary and volume flow. Europe leadership has been maintained over time (Fig. 7).

Elaborated squid and cuttlefish

The trade networks based on monetary value and volume for elaborated squid and cuttlefish emerge as global and complex, where several far distant traders have relevant roles in the import/export network (Supplementary Fig. S8). Although the most important nodes in the volume-based network reflected important nodes in the monetary value network, the strengths of the links, i.e., the flow of value and volume, did not. For example, in the volume-based network, Peru exported the largest quantities of squid and cuttlefish to China (Supplementary Fig. S8b,d), but the flow of money for these transactions was less important (Supplementary Fig. S8a,c).

The betweenness centrality metric (based both on monetary value and volume) showed the importance of China, the USA, and Spain (followed by Italy, Korea, and Thailand) as facilitators in the elaborated goods trade network (Supplementary Fig. S9). While the main important bridges in volume transactions were between Italy and Spain, Spain and China, and China and the USA (Supplementary Fig. S9b,d), the main monetary bridges were from the USA to China, followed by the routes from Spain to the USA and from Italy to Spain (Supplementary Fig. S9a,c). The key traders structuring the network were the same, but they follow different directions.

Closeness centrality highlighted the main actors in a regional context (Fig. 8). In both the monetary value and volume-based networks, China, North and South Korea, India, Indonesia, Thailand, and Vietnam form a strong trade network for squid and cuttlefish elaborated in Asia. Key players include South America (Peru, Argentina, Chile, the Malvinas/Falkland Islands); the USA; the Mediterranean (Morocco, Spain); Africa (South Africa, Mauritania); and the West Pacific region (New Zealand, Japan). Note how the highest values of closeness were slightly different in the money-based network (Fig. 8a) and in the volume-based network (Fig. 8b), mainly for those countries that are historically large producers of elaborated squid and cuttlefish (e.g., Peru and Argentina).

PageRank revealed the importance of Greece, Spain, China, USA and Japan as leading traders in the global elaborated squid and cuttlefish market for the first 10-years (Supplementary Fig. S10a). Globally, in the last decade, China, the USA and Japan have declined in importance, while Europe has consolidated its importance. However, Spain’s relevance has declined over the last decade while Germany’s has increased (Supplementary Fig. S10b).

Source: Ecology - nature.com