3.1. Trends of 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, and it has been reduced by 50% in the top 5 trading traders.
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. While Vietnam was the most important exporter in the first period (2000-2005), it has disappeared from the top 5 traders in the last five years. Imports have been dominated by Korea, Italy, and Portugal, with no notable changes in the whole period. 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. Since 2000, exports of processed products have been dominated by Morocco, Mauritania, China, Spain, and Vietnam, while imports have been led by Japan, Spain, Italy, Korea, and the United States.
Trade of fresh cuttlefish and squid in volume includes some 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). For the first five 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. 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. 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) became more relevant. 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 significant. A disparity exists between the top five traders in terms of monetary value flow and volume flow in the first fifteen years; but in the last five years the top positions are constant, with China, Peru, India, and Spain dominating. 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 five years.
The CGTN involves 220 traders (countries or territories) around the globe (Fig. 3). The remaining 32 traders either have no reported exports or were negligible (less than 500 kg in 20 years). The most important cluster of traders is 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 most relevant cluster is composed by 11 traders involving 3 developed (Belgium, Canada, Denmark) and 8 developing countries (Argentina, Chile, Malaysia, Morocco, Philippines, Senegal, South Africa, UAE). Some of these traders have the most productive cephalopod fisheries in the world (e.g., Patagonian shortfin squid in the Southwest Atlantic Ocean).
3.2. Octopus trade network
3.2.1. 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. Other relevant traders are Spain, Portugal and Italy in Europe, and Vietnam in Asia. The network based in volume shows similar results.
‘Betweenness’ identifies important actors facilitating flow through the network. For fresh octopus, the most relevant traders are 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 changes when considering volume, as Italy replaces France in the second place, Indonesia adopts a more key role, and the most important bridge moves from Spain-Thailand to Spain-the USA (Fig. S1).
Traders with a higher closeness have a high probability of exporting to the nearest neighbouring countries or territories; this measure also identifies important traders in a regional context. The traders with the highest closeness considering the monetary value and volume networks are China, Spain, Portugal, and Vietnam (Fig. S2). The Eigenvector reveals traders that are well connected in the network, identifying their area of influence within the network (traders with which they are connected). In this case, there are differences between the monetary value and volume networks. The influential nodes in the monetary value network are European traders including the Netherlands, Ireland, Belgium, and Romania. On the other hand, the influential traders regarding the volume network are globally distributed, including Indonesia, Canada, Russia, Republic of Korea, the Netherlands, and Czech Republic (Fig. 5).
Traditionally, Indonesia has acted as a hub importing a large volume (kg) of fresh octopus from 37 traders (e.g., India, Philippines, Vietnam, Singapore, Slovenia) and redistributing it to over 200 traders. Other traders that act as worldwide hubs are Slovakia (Europe), Canada (North America), Peru (South America) and Kenya (Africa). Regarding monetary flow, Peru appears as the most important hub. Although Peru is a large producer, it imports fresh octopus from Chile which it then markets to over 26 traders (Fig. S3).
Authority scores for the volume network reveal which traders have multiple import routes and strong preferential relationships with specific buyer traders in the network (e.g., Czech Republic, Russia, Korea, Canada) (Fig. S4 top). For the monetary value network, Authority scores reveal which traders import from many sources then export to a few destinations while increasing the value of the product. Traders with high Authority scores for the monetary value network could be acting as regulatory actors of the selling price (e.g., Belgium, the USA, the Netherlands, Spain, Hong Kong, Brazil, Japan, Canada, Chile) (Fig. S4 bottom).
3.2.2. Elaborated octopus
The normalised strength reveals a diversified trade network for elaborated octopus products. Several relevant actors are distributed globally (e.g., Spain, Japan, Morocco, Mauritania, Italy, China, Republic of Korea, Vietnam, Portugal, the USA) and are developing different important routes (e.g., from Morocco to Spain; from Mauritania and Morocco to Japan; from Mauritania to Spain and from China and Vietnam to Korea). These routes show a common pattern: the origin is in developing countries or territories (that emerge as producers) while developed countries show a high and stable consumer demand. The network based on volume is highly similar to the monetary value network. However, Italy, China, Korea, Vietnam, and the USA reduce their importance compared to the top-ranked traders (i.e., Spain, Japan, and Morocco). The most important routes of the volume network are from China to Korea; Morocco to Spain; Morocco and Mauritania to Japan and Vietnam to Korea (Fig. S5).
The Betweenness measure highlights the role of Spain as a facilitating actor in the trade network of elaborated octopus, followed by Italy, China, and the USA. Similarly, the routes from Italy to Spain, and from Spain to China and the USA emerge as relevant in the network structure (Fig. 6). There are no major differences between the most central traders in this network and the volume-based one. Notably, the route between the USA and the Philippines is more important in the volume-based network (Fig. S6).
The most important traders according to the closeness measure for both the monetary value network and the volume-based network are Morocco, Mauritania, China, Vietnam, and Spain. These traders may place their commodities quickly and effectively in the network, influencing the transactions of their closest partners (Fig. S7).
The eigenvector reveals the foremost importance of the Netherlands as a gateway for elaborated octopus to the European market, both in monetary value and volume (Fig. S8). Other European traders with a high eigenvector in the monetary value network are Malta, Lithuania, Cyprus and the United Kingdom. Elsewhere, China and Japan play a key role (Fig. S8 top). Central and Eastern European traders also have high eigenvector values in the volume-based network (e.g., Estonia, France, Lithuania, Luxembourg, Poland, Slovenia, Austria), highlighting a strong network of connections across the continent (Fig. S8 bottom).
The hub scores for monetary value and volume-based networks for elaborated octopus mostly highlight European traders as actors that buy from few sources and sell to several partners (Fig. S9). The Authority score again reveals the foremost importance of the Netherlands as a gateway to the European market, both in monetary value and volume. The Netherlands is a trader with many import routes that sells to few traders, mostly in Europe (Fig S10).
3.3. Squid and cuttlefish trade network
3.3.1. 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. 7). The volume-based network (Fig. S11 bottom) is highly similar to the monetary value network.
For fresh squid and cuttlefish, Betweenness identifies Spain as leading the worldwide trade flow in both monetary value and volume networks, while Italy, France, India, China, and the USA are facilitators in terms of both monetary value and volume. However, in the volume-based network, the Netherlands and Myanmar stand out, forming a bridge between the European and Asian markets (Fig. 8).
According to the closeness centrality measure for monetary value and volume-based networks, India may be able to commercialize fresh commodities quickly and effectively among its trading partners (Fig. S12). To a lesser extent, this property is also observed for France, Spain, Yemen, and Morocco.
The Eigenvector score reveals a similar pattern to that emerging from the fresh octopus network, highlighting many quality links among European traders (i.e., relationships with other well-connected traders) in the volume-based network. In this network, the Netherlands is revealed as an important gateway to Europe. In Asia, Thailand takes this role. In the monetary value network, Peru stands out due to its strategy of sourcing only from Chile and redistributing to 26 traders around the world (Fig. S13).
Hub centrality highlights Peru in the monetary value network. This may be driven by its role as an accumulator of fresh commodities from Chile, and exporter to traders with a dominant position in cephalopod pricing (Fig. S14). Authority centrality highlights several traders around the world in the monetary value network: Thailand, Korea, Canada, Denmark, South Africa, Singapore, Chile, Australia, and Spain. In the volume-based network, the central traders are European, with Ireland and the Netherlands at the top, while the rest of the world is dominated by Singapore and Thailand (Fig. S15).
3.3.2. Elaborated squid and cuttlefish
The trade networks based in 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 (Fig. 9). Although the most important nodes in the volume-based network reflect important nodes in the monetary value network, the strengths of the links, i.e., the flow of value and volume, do not. For example, in the volume-based network, Peru exports the largest quantities of squid and cuttlefish to China (Fig. 9 bottom), but the flow of money for these transactions has lower importance (Fig. 9 top).
The betweenness centrality metric (both monetary value and volume based) shows the importance of China, the USA, and Spain (followed by Italy, Korea, and Thailand) as facilitators in the processed goods trade network (Fig. S16). While the main bridges in volume transactions are between Italy and Spain, Spain and China, and China and the USA (Fig. S16 top), the main monetary bridges are from the USA to China, followed by the routes from Spain to the USA and from Italy to Spain (Fig. S16 bottom). That is, the key protagonists are the same, but they follow different directions.
Closeness centrality highlighted the main actors in a regional context (Fig. 10). 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 processed 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) (Fig. 10).
The eigenvector centrality shows the most important international gateways for the monetary value and volume-based networks and their main destinations. For example, the Netherlands and neighbouring destination traders within Europe; Indonesia, Singapore, Korea and Japan on the Asian continent; or South Africa or the United Arab Emirates in the rest of the world (Fig. S17).
The combined hub score of the monetary value and volume-based networks identifies hubs and redistributors of elaborated squid and cuttlefish products around the world: Indonesia, Japan, Thailand, the Netherlands, Portugal, Poland, United Kingdom, and many other European traders (Fig. S18).