Seaweed aquaculture represents 96.5 percent of the world’s seaweed supply. Seaweeds were the first group of organisms to pass the 50 percent farmed/wild harvest threshold in 1971. This occurred in 1986 for freshwater fishes, 1994 for molluscs, 1997 for diadromous fishes and 2010 for crustaceans. In 2016, fish aquaculture represented 47 percent of total global fish production (i.e. considering food plus non-food uses) and 53 percent of total food fish production. Over two decades (1995-2004; 2005-2014), the average annual production growth rate for fish declined from 7.2 percent to 5.8 percent, while that for seaweeds increased from 6.2 percent to 8.0 percent.
Dr Thierry Chopin
Seaweed aquaculture: mostly an Asian affair
Seaweeds: The world’s largest mariculture crop
W
ith an annual world production of 30.1 million tonnes, worth US$11.7 billion, seaweeds have represented the largest group of marine and coastal aquaculture (mariculture) organisms since 2004, reaching 51.2 percent in 2016 (see Table 1), according to the FAO’s 2018 State of the World Fisheries and Aquaculture, which uses data collected up to 2016. Molluscs, which were the largest group of organisms until 2000, when they represented 46.2 percent of the world mariculture production, is now the second group, having decreased to 28.7 percent. Finfish, which are so much the focus in the western world, represent only around 11 percent worldwide since 2012 (11.2% in 2016). So, aquaculture is not synonymous with fish aquaculture, or salmon aquaculture, everywhere; there are other models in the world and we should learn from them. Crustacean production increased to 12 percent in 2014, but reduced to 8.2 percent in 2016, similar to the 2012 production. Other aquatic animals (turtles, sea cucumbers, sea urchins, frogs, alligators, crocodiles, jellyfish, etc.) remain a very small fraction of the overall world production (0.7% in 2016). When considering freshwater aquaculture production, seaweeds represent 27.3 percent of the world total (marine, coastal and freshwater) aquaculture production, as the inclusion of massive Chinese carp production has a significant impact on statistics.
There are approximately 10,500 known species of seaweeds. Around 500 species have been used for centuries for human food and medicinal purposes, directly as food (mostly in Asia) or indirectly for the compounds that can be extracted from them (e.g. phycocolloids such as agars and carrageenans extracted from red seaweeds and alginates extracted from brown seaweeds). There are, however, only approximately 220 species of seaweeds cultivated worldwide. Nine genera (six groups) provide 96.1 percent of the aquaculture production: Kappaphycus/Eucheuma (40.7%), Saccharina/Laminaria (27.3%), Gracilaria (13.8%), Undaria (6.9%), Porphyra/Pyropia (6.8%) and Sargassum (0.6%; see Figure 1). Not surprisingly, not many of the above statistics are known in the western world, because 99.4% of the seaweed aquaculture activities are concentrated in 7 Asian countries: China (47.9%), Indonesia (38.7%), the Philippines (4.7%), the Republic of Korea (4.5%), the Democratic People’s Republic of Korea (1.6%), Japan (1.3%) and Malaysia (0.7%). However, we should not be surprised that we cultivate only a few groups of seaweeds. After all, we mostly eat and grow four marine fish (salmon, sea bass, cod and tuna) and five terrestrial animals (chicken, pig, turkey, sheep and cow). Humans usually cultivate what is easy to grow and with low juvenile mortality. Moreover, as explained in my July column, seaweeds do not have much in common and are an unnatural grouping. Because they have very different life histories, their culture techniques vary widely. If Saccharina, Laminaria and Undaria are cultivated in a similar fashion, the cultivation techniques of the four other groups are completely different from these three kelps and among themselves. It would not be a far stretch to say that farming brown, red and green seaweeds is as different as farming alligators, kangaroos and chickens!
Table 1: Distribution of worldwide mariculture production among the main types of cultivated organisms (based on FAO data between 1998 and 2018) Production (%)
1996
2000
2004
2008
2010
2012
2014
2016
Molluscs
48.0
46.2
43.0
42.7
37.2
30.7
28.0
28.7
Seaweeds
44.0
44.0
45.9
46.2
50.9
49.1
47.5
51.2
Finfish
7.0
8.7
8.9
8.9
9.1
11.4
11.0
11.2
Crustaceans
1.0
1.0
1.8
1.8
1.8
8.1
12.0
8.2
-
0.1
0.4
0.4
1.0
0.7
1.5
0.7
Other aquatic animals
14 | August 2018 - International Aquafeed
Table 2: Distribution of the world total aquaculture production between extractive and fed organisms (based on 2018 FAO data) Extractive aquaculture Seaweeds + aquatic plants
27.3%
Molluscs
15.5%
Non-fed finfish
8.0%
50.8%
Fed aquaculture Fed finfish
41.1%
Crustaceans
7.2%
Other aquatic animals
0.9%
49.2%