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INVITED EDITORIAL
Importance of Seaweeds and Extractive Species in Global
Aquaculture Production
Thierry Chopin
a
and Albert G. J. Tacon
b
a
Seaweed and Integrated Multi-Trophic Aquaculture Research Laboratory, University of New Brunswick, Saint John, New Brunswick,
Canada;
b
Aquahana LLC, Kailua, Hawaii, USA
ABSTRACT
The FAO recently published its biennial State of World Fisheries and Aquaculture up to 2018.
The FAO continues to treat the seaweed aquaculture sector as a different category, with sep-
aratetablesandcommentsindifferentsections.Asthiscouldleadtoadistortedviewoftotal
world aquaculture, the statistical information provided by FAO was revisited and data regard-
ing the seaweed aquaculture sector were integrated with data of the other sectors of the
world aquaculture production, to reach different conclusions: (1) aquaculture represents
54.1% of total world fisheries and aquaculture production; (2) marine and coastal aquaculture
represents 55.2% of total world aquaculture production; (3) seaweeds represent 51.3% of total
production of marine and coastal aquaculture; (4) 99.5% of seaweed mariculture production is
concentrated in Asia; (5) 8 seaweed genera provide 96.8% of world seaweed mariculture pro-
duction; (6) 2 seaweed genera are the most produced organisms in mariculture in the world;
(7)thevalueoftheseaweedaquaculturesectorcouldbemuchlarger,especiallyifamonet-
ary value was attributed to the ecosystem services provided by seaweeds; and (8) total
extractive aquaculture is slightly larger (50.6%) than total fed aquaculture (49.4%).
KEYWORDS
Aquaculture statistics;
extractive species; FAO; fed
species; seaweeds; seaweed
aquaculture
Introduction
The FAO recently published The State of World
Fisheries and Aquaculture (FAO 2020a), its biennial
document, which contains a wealth of information on
both fisheries and aquaculture throughout the world.
While FAO should be commended for giving more
and more attention to seaweed aquaculture production,
it continues to treat the seaweed aquaculture sector as
a different category, with separate tables and separate
comments in different sections. This could lead to a
distorted view of what really constitutes the total world
aquaculture (Chopin 2012). For that reason, the statis-
tical information provided by FAO was revisited and
data regarding the seaweed aquaculture sector were
integrated with the data of the other sectors of the
world aquaculture production (mostly fish, molluscs
and crustaceans), to demonstrate how a combined ana-
lysis can modify the conclusions reached.
Distribution between world fisheries and
aquaculture production
In Table 1 of the latest FAO report (FAO 2020a), total
capture fisheries landings are reported as 96.4 million
tonnes (expressed on a “live weight”basis, as all other
numbers here after) and total aquaculture production
as 82.1 million tonnes, in 2018. However, a footnote
at the bottom of the table states that this table
“excludes aquatic mammals, crocodiles, alligators and
caimans, seaweeds and other aquatic plants.”Clearly,
this footnote can easily be overlooked by readers, and,
consequently, the conclusion that can be reached is
that capture fisheries represent 54.0% and aquaculture
represents 46.0% of the total world fisheries landings
and aquaculture production (178.5 million tonnes;
FAO 2020a).
If the worldwide production of aquatic mammals,
crocodiles, alligators and caimans is relatively small
and poorly documented in data, that of seaweeds is
significantly large and should not be ignored (32.4
million tonnes, valued at US$13.3 billion). In marked
contrast, the harvesting of wild seaweeds represented
only 2.9% of the total global reported seaweed pro-
duction or 0.9 million tonnes in 2018. Consequently,
including these data, capture fisheries (97.3 million
tonnes) represent 45.9%, and aquaculture (114.5 mil-
lion tonnes) now represents 54.1% of the total world
CONTACT Thierry Chopin tchopin@unbsj.ca Department of Biological Sciences, University of New Brunswick Saint John, 100 Tucker Park Rd, Saint
John, Canada NB E2L 4L5.
ß2020 Taylor & Francis Group, LLC
REVIEWS IN FISHERIES SCIENCE & AQUACULTURE
2021, VOL. 29, NO. 2, 139–148
https://doi.org/10.1080/23308249.2020.1810626
fisheries landings and aquaculture production (211.8
million tonnes) in 2018.
Moreover, throughout the FAO document, and on
Table 9 (p. 32), the value of 32.4 million tonnes of
farmed seaweed production is used; however, on p.
29, it is indicated that “In 2018, farmed seaweeds rep-
resented 97.1 percent by volume of the total of 32.4
million tonnes of wild-collected and cultivated aquatic
algae combined.”In that case, that would mean 0.9
million tonnes of wild-collected seaweeds and 31.5
million tonnes of aquaculture seaweeds. Accordingly,
the above numbers could be further adjusted to show
that capture fisheries (97.3 million tonnes) represent
46.1% and aquaculture (113.6 million tonnes) repre-
sents 53.9% of the total world fisheries landing and
aquaculture production (210.9 million tonnes).
Consequently, the “farming more than catch”mile-
stone was definitely reached by 2018, if the seaweed
sector were to be considered in the total statistics.
Seaweeds were the first group of organisms to reach
the “farming more than catch”milestone in 1971
(Chopin 2018c). Since then, farmed freshwater fish pro-
duction reached this milestone in 1986, farmed mollusc
production in 1994, farmed diadromous fish produc-
tion in 1997 and farmed crustacean production in
2010. However, according to the FAO, the production
of farmed marine fish is not expected to overtake mar-
ine capture production in the near future (FAO 2020a).
Distribution of worldwide aquaculture
production by major species groups
If seaweed aquaculture production is considered, mar-
ine and coastal (ponds and lagoons) aquaculture (63.2
million tonnes) represented 55.2% of the total world
aquaculture production (114.5 million tonnes), and
inland aquaculture (mostly freshwater; 51.3 million
tonnes) represented 44.8% of the total aquaculture
production in 2018 (FAO 2020a).
Considering only marine and coastal aquaculture,
seaweeds (32.4 million tonnes) represented 51.3%,
followed by molluscs (17.3 million tonnes, 27.4%), fin-
fish (7.3 million tonnes, 11.6%), crustaceans (5.7 mil-
lion tonnes, 9.1%) and other aquatic animals (0.4
million tonnes, 0.6%) in 2018 (FAO 2020a).
Moreover, reviewing FAO statistics data between
1996 and 2018 (FAO 1998,2002,2006,2010,2012,
2014, 2016, 2018), molluscs dominated the world
mariculture production until 2000 (46.2%) and there-
after were overtaken by seaweeds (45.9% in 2004).
Seaweeds now represent more than half of the marine
and coastal aquaculture production (around 51%),
while molluscs represent around 28%. Finfish and
crustacean productions are way behind, with around
11% and 9% in the last few years (Table 1).
Seaweed mariculture production is
concentrated in 9 Asian countries and
territories
Over the last two decades, seaweed mariculture has
taken place mainly within 9 east and southeast Asian
countries and territories (depending on how one con-
siders the status of Taiwan) (Table 2): from 98.9% in
2000 to 99.5% in 2018. Zanzibar (United Republic of
Tanzania) and Chile produced very small amounts
(0.3 and 0.1%, respectively) of the world seaweed
aquaculture production. All other countries in the
world, combined, produced only 0.1%.
Global seaweed aquaculture production increased by
40.0% between 2000 (10.6 million tonnes) and 2005
(14.8 million tonnes), then by 36.0% to 2010 (20.2 mil-
lion tonnes), and 53.4% to 2015 (31.1 million tonnes).
Between 2015 and 2018, the world seaweed aquaculture
production fluctuated around 32 million tonnes. After
a tripling of the seaweed production over 16 years, this
stabilization seems to be mostly caused by the slowing
growth in the farming of tropical species in southeast
Table 1. Distribution of worldwide mariculture production
between the main types of cultivated organisms from 1996 to
2018 (based on FAO live weight data between 1998 and 2020).
a
World mariculture production (%)
1996 2000 2004 2008 2010 2012 2014 2016 2018
Molluscs 48.0 46.2 43.0 42.7 37.2 30.7 28.0 28.7 27.4
Seaweeds 44.0 44.0 45.9 46.2 50.9 49.1 47.5 51.2 51.3
Finfish 7.0 8.7 8.9 8.9 9.1 11.4 11.0 11.2 11.6
Crustaceans 1.0 1.0 1.8 1.8 1.8 8.1 12.0 8.2 9.1
Other aquatic
animals
–0.1 0.4 0.4 1.0 0.7 1.5 0.7 0.6
a
FAO (1998, 2002, 2006, 2010, 2012, 2014, 2016, 2018, 2020a).
Table 2. Seaweed mariculture production by major producers.
2000 2018
China 8,227.6 (77.7) 18,505.7 (57.1)
Indonesia 205.2 (1.9) 9,320.3 (28.8)
Republic of Korea 374.5 (3.5) 1,710.5 (5.3)
Philippines 707.0 (6.7) 1,478.3 (4.6)
Democratic People’s Republic of Korea 401.0 (3.8) 553.0 (1.7)
Japan 528.6 (5.0) 389.8 (1.2)
Malaysia 16.1 (0.2) 174.1 (0.5)
China, Taiwan …69.6 (0.2)
Viet Nam 15.0 (0.1) 19.3 (0.1)
Total Asian seaweed mariculture
production
10,475.0 (98.9) 32,220.6 (99.5)
Zanzibar, United Republic of Tanzania 49.9 (0.5) 103.2 (0.3)
Chile 33.5 (0.3) 20.7 (0.1)
Other producers in the world 37.1 (0.3) 41.6 (0.1)
Total world seaweed mariculture
production
10,595.6 (100) 32,386.2 (100)
Numbers are in thousand tonnes live weight (FAO 2020a); numbers in
brackets are percentages.
140 T. CHOPIN AND A. G. J. TACON
Asia, while farming of temperate and coldwater species
is still rising. There has been significant progress in
North America, Europe and South America, mostly
through the development of integrated multi-trophic
aquaculture (IMTA), promoting the ecosystem services
seaweeds can provide and the IMTA multi-crop diver-
sification approach as an economic risk mitigation and
management option to address pending climate change
and coastal acidification impacts (Carras et al. 2020).
However, most often, data are not available because of
confidentiality issues due to the small number of pro-
ducers involved.
China’s share has decreased from 77.7% in 2000 to
57.1% in 2018, although seaweed production in that
country has more than doubled over this period
(Table 2). This is mostly due to the sharp increase in
the production of the carrageenophytes Eucheuma and
Kappaphycus in Indonesia, now producing 28.8% of
the world seaweed aquaculture production. The pro-
duction of the Republic of Korea has been multiplied
by a factor of 4.6, while its share of the world produc-
tion has increased modestly by 1.8%. The production
of the Philippines has doubled; however, its share of
the world production has decreased by 2.1%. The pro-
duction of Japan has been constantly decreasing and
now represents only 1.2% of the world production.
Eight genera provide most of the world
seaweed mariculture production
There are approximately 10,500 known species of sea-
weeds (Chopin 2018c). Around 500 species have been
used for centuries for human food and medicinal pur-
poses, either directly as food ( primarily within Asian
countries; MacArtain et al. 2007; Pereira 2011; Tacon
and Metian 2013) 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 sea-
weeds) (Chopin 2018b). Although over 220 species of
seaweeds are reportedly cultivated worldwide, only 20
species were listed in the FAO FISHSTAT database
for 2018 (FAO 2020b).
Eight genera provided 72.3% (7.7 million tonnes)
of the world seaweed aquaculture production in 2000
and provided 96.8% (31.3 million tonnes) in 2018:
Saccharina japonica (known as kombu and previously
described as Laminaria japonica; 35.3%), the carragee-
nophytes Eucheuma (29.0%), the agarophytes
Gracilaria (10.7%), Porphyra and Pyropia (known as
nori; 8.9%), Undaria pinnatifida (known as wakame;
7.2%), the carrageenophytes Kappaphycus (4.9%) and
Sargassum (0.8%) (Table 3).
Until 2010, there were always more brown seaweeds
produced (11.1 million tonnes) than red seaweeds (8.9
million tonnes). In 2015, this ratio changed, as more
red seaweeds were produced (17.8 million tonnes) than
brown seaweeds (13.2 million tonnes), mostly due to a
major increase in the carrageenan producing species of
the genus Eucheuma and the agar producing species of
the genus Gracilaria. Brown seaweeds are mostly used
for direct human consumption, the production of other
phycocolloids, called alginates, and other applications
(Chopin and Sawhney 2009).
Seaweeds the most produced organisms in
mariculture
By combining the data of Table 8 (p. 30–31) and
Table 9 (p. 32) of the FAO (2020a) document, one
Table 3. The eight genera providing the majority of the world
seaweed mariculture production with the other algae combined
to make the total world seaweed mariculture production.
2000 2018
Red seaweeds
Eucheuma spp. 299.6 (2.9) 9,412.4 (29.0)
Kappaphycus spp. 649.5 (6.1) 1,597.3 (4.9)
Gracilaria spp. 55.5 (0.5) 3,454.8 (10.7)
Porphyra/Pyropia spp. (nori) 954.1 (9.0) 2,872.8 (8.9)
Total red seaweeds 1,958.7 (18.5) 17,337.3 (53.5)
Brown seaweeds
Saccharina japonica (kombu) 5,380.9 (50.8) 11,448.3 (35.3)
Undaria pinnatifida (wakame) 311.1 (2.9) 2,320.4 (7.2)
Sargassum spp. 12.1 (0.1) 268.7 (0.8)
Other Phaeophyceae 2,852.8 (26.9) 891.5 (2.8)
Total brown seaweeds 8,556.9 (80.7) 14,928.9 (46.1)
Other algae 79.9 (0.8) 119.9 (0.4)
Total world seaweed mariculture
production
10,595.6 (100) 32,386.2 (100)
Numbers are in thousand tonnes live weight (FAO 2020a); numbers in
brackets are percentages.
Table 4. Major organisms produced in world
mariculture in 2018.
Saccharina japonica (kombu) 11,448.3
Eucheuma spp. 9,412.4
Crassostrea spp. (oysters) 5,814.6
Penaeus vannamei (whiteleg shrimp) 4,966.2
Ruditapes philippinarum (Manila clam) 4,139.2
Gracilaria spp. 3,454.8
Porphyra spp. 2,872.8
Salmo salar (Atlantic salmon) 2,435.9
Undaria pinnatifida (wakame) 2,320.4
Sea scallops 1,918.0
Kappaphycus spp. 1,597.3
Mussels 1,570.7
Sinovovacula constricta (Chinese razor clam) 852.9
Penaeus monodon (giant tiger prawn) 750.6
Anadara granosa (blood cockle) 433.4
Sargassum spp. 268.7
Apostichopus japonicus (Japanese sea cucumber) 176.8
Brown seaweeds (brown), red seaweeds (red), molluscs
(green), crustaceans (yellow), finfish (grey), and holothur-
ians (blue). Numbers are in thousand tonnes live weight
(FAO 2020a).
REVIEWS IN FISHERIES SCIENCE & AQUACULTURE 141
realizes that, in 2018, two genera of seaweeds, the
brown seaweed Saccharina and the red seaweed
Eucheuma, were the two most produced organisms in
mariculture in the world (Table 4).
In fact, when reviewing the top seven most produced
mariculture species, there are 4 genera of seaweeds, 2 gen-
era of molluscs and 1 genus of crustaceans. The first fin-
fish (Atlantic salmon, Salmo salar)isfoundineighth
position, followed closely by the brown seaweed Undaria
in ninth position. Another carrageenophyte, Kappaphycus,
is in the eleventh position.
Value of the seaweed aquaculture sector
FAO indicates a farm-gate value of US$13.3 billion
for the world seaweed aquaculture production (FAO
2020a). Estimating the true value of the different sea-
weed markets is difficult, as seaweed applications are
numerous (Chopin 2018b) and some lucrative emerg-
ing markets are presently in full expansion while
others need to be further developed.
The phycocolloid sector, predominant in the
1970s–1990s, now represents only a minor part (11.4%
of the tonnage and 10.8% of the value) of an industry
in full mutation. The use of seaweeds as sea-vegetables
for direct human consumption has become much more
significant (77.6% of the tonnage and 88.3% of the
value). Five genera dominate the edible seaweed mar-
ket: Saccharina and Laminaria (kombu), Undaria (wak-
ame), and Porphyra and Pyropia (nori). If the use of
seaweeds as edible human food is well-established in
Asian countries, a lot of work is still needed to educate
westerners regarding cooking with seaweeds and going
beyond the superfood fad, to have them understand
the benefits of including these crops in their regular
diet. The phycosupplement industry is a fast emerging
component (11.0% of the tonnage and maybe an
underestimated 0.9% of the value). This includes soil
additives, agrichemicals (fertilizers and biostimulants),
animal feeds (supplements and ingredients; increasingly
for aquaculture), fine and bulk chemicals, small biopol-
ymers, pharmaceuticals, cosmetics and cosmeceuticals,
Figure 1. Integrated sequential biorefinery (ISBR) approach to the processing of seaweeds.
142 T. CHOPIN AND A. G. J. TACON
nutraceuticals, functional foods, biooils, health bioactive
and anti-applications (anti-oxidants, anti-cancer, anti-
microbial, anti-viral, anti-inflammatory, anti-diabetic,
etc.), botanicals, pigments, colorants, aromatics, brew-
ing components, biomaterials/biocomposites, thermo-
plastics, adhesives, etc.
An area of interest to the commercial aquafeed sec-
tor has recently been the use of seaweed-enriched
media. Substitution of fishmeal by other protein sour-
ces has been investigated in recent years, mostly con-
sidering land-plant proteins. There is now an interest
in seaweeds as substrate for growth and nutritional
enhancement. In a literature review, Chopin (2019)
found 107 papers, in which a portion of the feed was
replaced with seaweeds: 61 involved the culture of fish
(40 of marine fish and 21 of freshwater fish), 24 the
culture of crustaceans (shrimp, prawn, lobster), 11 the
culture of molluscs (various species of abalone), 10
the culture of echinoderms (sea urchins) and 1 the
culture of holothurians (sea cucumbers). These papers
demonstrated that substitution of fishmeal by various
seaweeds (29 species from 13 genera), generally not in
excess of 5–15% (but with exceptions up to 20, 30
and even 50% in some species), has potential in man-
ufacturing new formulations triggering better growth
and other benefits in diverse organisms already aqua-
cultured, or whose cultivation is being developed.
Further studies are required to determine the best mix
of seaweed species and ratios. The wild-harvested
brown seaweed Ascophyllum nodosum (rockweed) has
also been used to modulate the nutrient composition
(omega-3 fatty acids and vitamin E) of larvae of
Hermetia illucens (black soldier fly), then used in fish
feed (Liland et al. 2017).
For too long, seaweeds, like other fishery and aqua-
culture products, have been processed according to a
simple scheme: one species—one process—one product.
However, seaweeds remain a relatively untapped
resource with a huge potential for integrated sequential
biorefinery (ISBR) processing (Figure 1). Society will
have to change its attitudes and business models to
evolve from this linear approach to move toward the
ISBR approach (one species—several processes—several
products) within a circular economy framework, where
there are no longer wastes and by-products, but co-
products, which can also be marketed. With careful
planning at the time of harvesting, and with sequential
processing, more than one product can be manufac-
tured from seaweeds: on one hand, a wide range of
bio-based, high-value compounds (cited above); on the
other hand, lower-value commodity energy compounds
(biofuels, biodiesels, gasoline, waxes, olefins, biogases,
bioalcohols, aldehydes, acids, heat/steam and power/
electricity generation, etc.).
The price of seaweeds varies greatly, depending on
the applications and their added values (Figure 2):
Figure 2. Variability of the price of seaweeds according to their applications, markets and the added value of seaweed products.
This is a pyramidal structure as the product volume decreases as the product value increases (values in US$).
REVIEWS IN FISHERIES SCIENCE & AQUACULTURE 143
from less than US$1/kg (if seaweeds want to be com-
petitive as biofuels compared to the existing fossil bio-
fuel, i.e. petroleum) to more than US$1,000/kg for
pharmaceuticals and bioactives.
Moreover, to calculate the full value of seaweeds,
these extractive species need to be valued for not only
their biomass and food trading values, but also for the
ecosystem services they provide, along with the increase
in consumer trust and societal/political license to oper-
ate that they give to the aquaculture industry in general
(circular economy approach) (Barrington et al. 2010;
Mart
ınez-Espi~
neira et al. 2015,2016).
One of the key ecosystem services provided by sea-
weeds is nutrient biomitigation and a monetary value
can be calculated for this service. If 1) the compos-
ition of seaweeds can be averaged at around 0.35%
nitrogen (N), 0.04% phosphorus (P) and 3% carbon
(C), 2) the recovery costs, calculated from wastewater
treatment facilities, are US$10–30/kg N and US$4/kg
P, and 3) a value of US$30/tonne C for carbon tax
schemes is used, then, the ecosystem services for
nutrient biomitigation provided by worldwide seaweed
aquaculture (32.4 million tonnes) can be valued at
between US$1.214 billion and US$3.482 billion, i.e. as
much as 26.2% of their present commercial value
(US$13.3 billion). The value of this important service
to the environment and, consequently, society has,
however, never been accounted for in any budget
sheets or business plans of seaweed farms and compa-
nies. Moreover, the other ecosystem services provided
by seaweeds should also be analyzed in a similar man-
ner to establish their own monetary values.
Much has been said about carbon sequestration and
the development of carbon trading taxes. In coastal envi-
ronments, mechanisms for the recovery of nitrogen and
phosphorus should also be highlighted and accounted for
in the form of nutrient trading credits (NTCs, a much
more positive approach than taxing, for those imple-
menting sustainable practices). It is interesting to note
that the value for C is per tonne, whereas those for N
and P are per kilogram. Nobody seems to have picked up
on that when looking at the sequestration of elements
other than C. There is more money to be made with
NTC (between US$1.134 and 3.401 billion for N and
US$51.82 million for P) than with carbon trading credits
(CTC; only US$29.15 million for C).
The recognition and implementation of NTCs
would give a fair price to seaweeds (and other extract-
ive aquaculture species). They could be used as finan-
cial and regulatory incentive tools to encourage
mono-aquaculturists to contemplate IMTA as a viable
aquanomic option to their current practices to develop
the nutritious and sustainable food production sys-
tems of the future.
Seaweeds can participate in the dietary shift toward
the consumption of sustainable, safe, equitable, resilient
and low-carbon sources of food from the ocean that will
reduce gas emissions and carbon footprints from animal
land-based food production systems, and contribute sig-
nificantly to climate change mitigation to keep global
temperature rises below 1.5 C, by 2050, to reach the tar-
gets of the Paris Agreement (Hoegh-Guldberg et al.
2019;Chopin2020). Moreover, seaweeds welcome vege-
tarians and vegans into the seafood world by offering
access to highly nutritious ocean-based, plant-equivalent
food sources from pristine waters (Pereira 2011;Tacon
and Metian 2013). By eating more seaweeds, people will
participate in the decarbonization of this world and con-
tribute, at their level, in helping to mature the Blue
Economy into the greener Turquoise Revolution.
Seaweeds for biofuel has been touted several times
over the last 10–15 years. However, some reality-check
is necessary at several levels. It is doubtful that the
surface area needed to secure the raw material for sig-
nificant biofuel production will be societally accept-
able, especially in the western world. Seaweed biomass
production is highly seasonal, while people refill at
gas stations 52 weeks of the year. Scaling up from
laboratory experiments to commercial markets needs
reality testing. Moreover, to be economically competi-
tive, seaweed biofuel would have to be at least as
cheap as the fossil biofuel presently used, i.e. petrol-
eum. Why try to sell seaweeds at several cents/tonne
fresh weight when they cannot be produced that inex-
pensively? On the contrary, seaweed farmers are inter-
ested in a spectrum of products commending much
higher prices (Figure 2).
More recently, some projects have developed the
idea of using seaweeds to sequester carbon and then to
bury them in the seabed to store carbon. However, sig-
nificant investment in additional research and develop-
ment would be required to ensure associated risks to
the marine environment are minimized prior to imple-
mentation at scale. Moreover, the value of the proposed
carbon tax schemes would have to be very significantly
increased to incite seaweed growers to sell their bio-
mass for burying when they can get much more money
selling it for much more lucrative applications.
Distribution of fed and extractive species
around the world
Aquaculture production can be divided into two
major groupings based on how they source their
144 T. CHOPIN AND A. G. J. TACON
nutrient inputs, namely the exogenously fed species and
the endogenously fed extractive species. Exogenously fed
species need to be externally fed with feeds added to the
culture system, while endogenously fed extractive species
either filter or graze on organic small and large particu-
late matter (invertebrates), or absorb dissolved inorganic
nutrients (seaweeds), already endogenously present in
the aquatic environment. It is interesting to compare
their level of production and worldwide distribution to
see if they strive toward a balance.
In the calculation of the total extractive aquaculture
(Table 5), inland aquaculture needs to be considered in
order to account for the significant production of 8 mil-
lion tonnes of filter-feeding and herbivorous fish (mainly
silver carp, Hypophthalmichthys molitrix,andbighead
carp, Hypophthalmichthys nobilis)producedinAsia.
Molluscs (mostly marine) add 17.5 million tonnes and
seaweeds add 32.4 million tonnes for a total extractive
aquaculture of 57.9 million tonnes. This means that total
extractive aquaculture is slightly higher (50.6%) than
total fed aquaculture (56.6 million tonnes or 49.4%).
Calculations for 2016, using FAO data (Chopin 2018c)
showed a similar distribution of 50.8% total extractive
aquaculture and 49.2% total fed aquaculture.
If considering only the total world mariculture produc-
tion (Table 5), then total extractive mariculture is even
higher (49.7 million tonnes or 78.7%) than total fed mari-
culture (13.5 million tonnes or 21.3%).
At first glance, one could rejoice at such a high per-
centage of extractive species; however, it is important to
remember that 99.5% of seaweed aquaculture is still con-
centrated within Asia. So, we have not yet balanced the
different production types of aquaculture at a worldwide
scale. Extractive aquaculture needs to be more evenly
distributed worldwide in an attempt at balancing fed
aquaculture. Moreover, what should be calculated is the
weight ratio of harvested extractive species required to
sequester an equivalent weight of nutrients loaded per
unit growth of fed species (Reid et al. 2013).
One solution to reach such a goal would be the
increased development of IMTA systems, especially in
the western world (Chopin et al. 2008). In these sys-
tems, the waste materials from fed species become co-
products to grow extractive species, considered as
additional crops reducing the nutrient load, hence
benefitting the environment though bioremediation,
while providing economic diversification with more
efficient practices within a circular economic approach
(Diana et al. 2013). FAO (2020a) recommends, on p.
25, 27, 29 and 125, integrated aquaculture, aquaponics
and polyculture and appears to encourage their devel-
opment for enhanced overall productivity, improved
resource-use efficiency, reduced impacts on the envir-
onment, and improved water quality by removing
waste materials and lowering the nutrient load.
It has recently been suggested (Dunbar et al. 2020)
that the use of fed species and extractive species should
be replaced by excretive species and extractive species.
We question the basis for such a proposition. After all,
seaweed and invertebrate extractive species also excrete.
What would be the fate of an organism if it was not
excreting? Sooner or later, it would become internally
toxified and/or explode. In recognizing the existence of
exogenously fed species, one acknowledges the fact that
these organisms have to be given feed (by humans),
which represents an additional input into the ecosys-
tem, while endogenously fed extractive species rely on
feed already present in the ecosystem (even if partially
originating from the co-products of the co-cultivated
exogenously fed species in IMTA systems) that they
will filter, graze upon or absorb.
Conclusions
Seaweeds are at the intersection of many topical
trends. They provide many inter-sectorial benefits: 1)
they are a source of food and many other applica-
tions; 2) they provide several key ecosystem services;
Table 5. Distribution of the total world aquaculture and mariculture production between extractive and fed organisms, in 2018.
Total world aquaculture production, including seaweed production
Total world mariculture production,
including seaweed production
Inland aquaculture Marine and coastal aquaculture Marine and coastal aquaculture
Extractive aquaculture
Seaweeds þaquatic plants —32,386.2 32,386.2
Molluscs 207 17,304 17,304
Non-fed finfish 8,000 ——
Total extractive aquaculture 57,897.2 (50.6) 49,690.2 (78.7)
Fed aquaculture
Fed finfish 38,951 7,328 7,328
Crustaceans 3,653 5,734 5,734
Other aquatic animals 528 390 390
Total fed aquaculture 56,584 (49.4) 13,452 (21.3)
Total aquaculture 114,481.2 (100) 63,142.2 (100)
Numbers are in thousand tonnes live weight (FAO 2020a); numbers in brackets are percentages.
REVIEWS IN FISHERIES SCIENCE & AQUACULTURE 145
3) they allow local diversification of a more balanced
aquaculture industry; and 4) they participate in the
dietary shift toward more decarbonized ocean-based
sources of proteins. Seeing FAO dedicating more time
and space to seaweeds in its 2020 version of its bien-
nial document The State of World Fisheries and
Aquaculture is, therefore, very much appreciated.
In several tables and figures, the FAO has a footnote
indicating “excludes aquatic mammals, crocodiles, alliga-
tors and caimans, seaweeds and other aquatic plants.”
Unfortunately, these footnotes can easily be overlooked
by readers who do not realize the consequences for data
interpretations, which can lead to incorrect conclusions.
By including the total seaweed aquaculture produc-
tion (32.4 million tonnes), as just another component
of the total world aquaculture production, it can be
concluded that, in 2018:
1. Aquaculture accounted for 54.1% of the total
world fisheries and aquaculture production;
whereas the FAO (not including the seaweed pro-
duction) mentioned that aquaculture accounted
for 46% of the total production.
2. Marine and coastal aquaculture produced 63.2
million tonnes, accounting for 55.2% of the total
world aquaculture production (114.5 million
tonnes); whereas the FAO mentioned that with a
production of 51.3 million tonnes of aquatic ani-
mals, inland aquaculture accounted for 62.5% of
the world’s farmed food fish production (82.1
million tonnes), while marine and coastal aqua-
culture (30.8 million tonnes) represented 37.5%.
3. Seaweeds (32.4 million tonnes) represent 51.3% of
the total production of marine and coastal
aquaculture, molluscs (17.3 million tonnes) repre-
sent 27.4%, finfish (7.3 million tonnes) represent
11.6%, crustaceans (5.7 million tonnes) represent
9.1% and other aquatic animals (0.4 million
tonnes) represent 0.6%; whereas the FAO indi-
cated that molluscs represent 56.3%, finfish repre-
sent 23.8%, crustaceans represent 18.6% and other
aquatic animals represent 1.3%.
4. Total extractive aquaculture is slightly larger (57.9
million tonnes or 50.6%) than total fed aquacul-
ture (56.6 million tonnes or 49.4%); whereas the
FAO mentioned that fed aquaculture (56.6 million
tonnes) has outpaced (68.9%) non-fed aquaculture
(25.5 million tonnes) accounting for 31.1%.
Consequently, the FAO is urged to consider sea-
weed aquaculture as another aquaculture component
and to include the data of this sector directly in tables,
figures and sections, among the data of the other sec-
tors in the animal, and marine and coastal aquacul-
ture categories. That way, one also comes to realize
that, in 2018, two genera of seaweeds were the two
most produced organisms in mariculture in the world.
Treating seaweed aquaculture separately can lead to a
distorted view of what really constitutes the total
world aquaculture (Chopin 2012).
It is not uncommon to see the words “algae,”
“aquatic algae,”“seaweeds,”“marine plants”and
“aquatic plants”used interchangeably, and without
consistency, in many papers and reports published in
non-phycological journals. The FAO could play a
major role in clarifying the situation. For example,
expressions such as “farmed aquatic algae, dominated
by seaweeds”are confusing. As micro-algal production
is not covered in the State of World Fisheries and
Aquaculture series, one can only wonder what the
remaining “aquatic algae”could be. If it were the
remaining “marine plants,”it would be seagrasses;
however, these true marine plants are not cultivated,
to our knowledge.
Seagrasses, which most probably came from the
sea, colonized land, acquired the capability of differen-
tiating roots (capable of attachment and nutrient
absorption, whereas seaweeds only have holdfasts cap-
able of attachment but not of absorbing nutrients)
and differentiated visible reproductive organs (i.e.
flowers; that is why they belong to the Phanerogams,
whereas seaweeds have hidden reproductive organs,
recognized mostly by specialists, and belong to the
Cryptogams). Seagrasses, then, recolonized the marine
environment about 75 to 100 million years ago
(Papenbrock 2012).
In fact, the seaweeds closest to plants are the green
seaweeds, which evolutionarily and molecularly speak-
ing are the ancestors of organisms that colonized the
land to become terrestrial plants (Graham et al. 2009).
However, these are not the most produced in aquacul-
ture and even aonori [species of the genera Ulva
(some previously described as Enteromorpha) and
Monostroma], cultivated in Japan, Korea and Taiwan,
is not produced in large enough quantities to be rec-
ognized in FAO statistics. The same applies to sea
grapes (different species of Caulerpa). The relationship
between plants and red seaweeds is not as direct if
one pays attention to the features of the chloroplasts
(also acquired through primary endosymbiosis), ultra-
structural arguments, and reproduction and cell div-
ision specificities. As for brown seaweeds, they do not
have anything to do with plants and are, in fact, closer
to the fungus-like, heterotrophic Oomycetes and
146 T. CHOPIN AND A. G. J. TACON
diatoms [again based on the features of the chloroplast
(acquired through secondary endosymbiosis), ultrastruc-
tural arguments and differences in the flagellar system].
As the confusion around the words “algae,”“seaweeds,”
“kelps”and “marine aquatic plants”is recurrent, Chopin
(2018a) dedicated his second column in International
Aquafeed to the clarification of these terms.
It is hoped that this paper contributes to clarifying
the rightful place of seaweeds in the total world mari-
culture and total world aquaculture productions, and
in the worldwide distribution of fed and extractive
species. Including them in comprehensive tables, fig-
ures, sections and chapters, with the other aquaculture
crops, would help simplify and improve the under-
standing of fisheries and aquaculture statistics to avoid
recurrent misconceptions about the aquaculture world
and enable it to be approached with a more holistic
perspective.
Paradoxically, seaweed production in global aqua-
culture suffers the same mistreatment as animal live-
stock production in global agriculture, in which it is
not given similar importance as the production of
plant food crops, including cereals, fruits, nuts, roots,
tubers, oilseeds, pulses and vegetables. The FAO
(2020b) lists 330 cultivated species in aquaculture, of
which 244 are fed species and 86 are extractive species
(66 species of molluscs and 20 species of seaweeds); in
agriculture, 158 species are recognized as cultivated,
with 140 species being plant crops and 18 species
being animal fed species.
Moreover, it is important to include seaweed aqua-
culture not only for its biological and environmental
aspects, but also for its economic and societal aspects.
According to FAO (2018), fisheries and aquaculture
are critical for the livelihoods of 59.5 million people
worldwide, 39 million people in capture fisheries and
20.5 million people in aquaculture. We are not sure if
these statistics reflect accurately the number of people
involved in seaweed aquaculture, in which women
represent a significant component, in variable propor-
tions along the value chain: early stages of cultivation
in “hatcheries,”cultivation, harvest, post-harvest arti-
sanal or industrial processing, value addition, trade,
marketing, sales, nutritious/low-carbon/diverse food
security and securing livelihoods. Different cultivation
techniques for different species of seaweeds are also
responsible for different levels of involvement and
empowerment of women, especially the need to use
motorized boats to access/harvest the crops versus the
ability to harvest them using non-motorized boats or
by foot at low tide (cultural preconceptions and per-
ceptions about gender roles, responsibilities and
control over production, resources, assets, credits,
training and technological transfers, decision-making
and leadership).
Disclosure statement
No potential competing interest was reported by
the authors.
ORCID
Thierry Chopin https://orcid.org/0000-0003-2981-7324
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