The State of World Fisheries and Aquaculture 2020

MILLION TONNES (LIVE WEIGHT)
Cured
Prepared or preserved
Non-food purposes
Live, fresh or chilled
Frozen
SOURCE: FAO.
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THE STATE OF WORLD FISHERIES AND AQUACULTURE 
2020
a fast-growing aquaculture industry, which 
increased the prices of fishmeal and fish oil. As a 
result, a growing share of fishmeal and fish oil 
is being produced from fish by-products. It is 
now estimated that these by-products are used to 
produce up to 25–35 percent of the total volume 
of fishmeal and fish oil, but regional differences 
exist. For example, by-product use in Europe was 
estimated at a comparatively high proportion 
of 54 percent of total production (Jackson and 
Newton, 2016). With no major increases in raw 
material expected to come from whole wild fish 
(in particular, small pelagics), any increase in 
fishmeal production will need to come from 
by-products, with different nutritional value, 
being lower in protein, but richer in minerals 
and amino acids in comparison with fishmeal 
obtained from whole fish. 
Nevertheless, fishmeal and fish oil are still 
considered the most nutritious and most 
digestible ingredients for farmed fish, as 
well as the major source of omega-3 fatty 
acids (eicosapentaenoic acid [EPA] and 
docosahexaenoic acid [DHA]). However, their 
inclusion rates in compound feeds for aquaculture 
have shown a clear downward trend, largely as 
a result of supply and price variation coupled 
with continuously increasing demand from the 
aquafeed industry. They are increasingly used 
selectively at specific stages of production, such 
as for hatchery, broodstock and finishing diets, 
and the incorporation of fishmeal and fish oil 
in grower diets is decreasing. For example, their 
share in grower diets for farmed Atlantic salmon 
is now often less than 10 percent.
With regard to direct human consumption, fish 
oil represents the richest available source of 
long-chain polyunsaturated fatty acids (PUFAs), 
which perform a wide range of critical functions 
for human health. However, the Marine 
Ingredients Organisation (IFFO) estimates that 
about 75 percent of annual fish-oil production 
still goes into aquaculture feeds (Auchterlonie, 
2018). Because of the variability of fishmeal 
and fish-oil production and associated price 
variations, many researchers are seeking 
alternative sources of PUFAs. These include 
stocks of large marine zooplankton, such as 
Antarctic krill (
Euphausia superba
) and the 
copepod 
Calanus finmarchicus
, although concerns 
remain over the impacts on marine food webs. 
Krill oil in particular is marketed as a human 
nutrient supplement, while krill meal is finding 
a niche in production of certain aquafeeds. 
However, there are practical challenges 
regarding the processing of this raw material, 
notably due to the need to reduce its fluoride 
content, and because the cost of zooplankton 
products is too high for their inclusion as a 
general oil or protein ingredient in fish feed.
Fish silage, a rich protein hydrolysate, is a 
less expensive alternative to fishmeal and fish 
oil, and it is increasingly being used as a feed 
additive, for example, in aquaculture and in the 
pet-food industry. Obtained by acidification and 
natural protein hydrolysis, silage has potential 
to improve growth and reduce mortality of fed 
animals (Kim and Mendis, 2006; Toppe 
et al.
, 
2018).
By-product utilization 
The expansion of fish processing has resulted 
in increasing quantities of by-products, which 
may represent up to 70 percent of processed 
fish. Historically, fish by-products were often: 
thrown away as waste; used directly as feed 
for aquaculture, livestock, pets or animals 
reared for fur production; or used in silage 
and fertilizers. However, other uses of fish 
by-products have been gaining attention over 
the past two decades, as they can represent a 
significant source of nutrition and can now be 
used more efficiently as a result of improved 
processing technologies (Al Khawli 
et al
., 2019). 
The great amount of processing by-products 
involves significant environmental and technical 
challenges due to their high microbial and 
enzyme load and their susceptibility to rapid 
degradation unless processed or stored properly. 
Thus, timely collection and treatment of these 
by-products is crucial for their further processing. 
The by-products are usually composed of 
heads (which represent 9–12 percent of total 
fish weight), viscera (12–18 percent), skin 
(1–3 percent), bones (9–15 percent) and scales 
(about 5 percent). 
Fish by-products can serve a wide range of 
purposes. Heads, frames, fillet cut-offs and 
skin can be used directly as food or processed 
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PART 1 
WORLD REVIEW
into fish sausages, pâté, cakes, snacks, gelatine, 
soups, sauces and other products for human 
consumption. Small fish bones, with a minimum 
amount of meat, are consumed as snacks in 
some countries. By-products are also used in 
the production of feed (not only in the form 
of fishmeal and fish oil), biofuel and biogas, 
dietetic products (chitosan), pharmaceuticals 
(omega-3 oils), natural pigments, cosmetics, 
alternatives to plastic, and constituents in other 
industrial processes. 
Enzymes and bioactive peptides can be obtained 
from fish waste and used for fish silage, fish feed 
or fish sauce production. There is also increasing 
demand for fish proteolytic enzymes, which can 
be isolated from fish viscera, because of their 
wide range of applications in leather, detergent, 
food and pharmaceutical industries, and in 
bioremediation processes (Mohanty 
et al
., 2018). 
Fish bones, in addition to being a source of 
collagen and gelatine, are also an excellent 
source of calcium and other minerals such as 
phosphorus, which can be used in food, feed or 
food supplements. Calcium phosphates present 
in fish bone, such as hydroxyapatite, can help 
regenerate bones after major trauma or surgery. 
Collagen is used for a variety of applications 
such as edible casings, cosmetics and biomedical 
materials for pharmaceutical applications. 
Fish gelatine is an alternative to bovine gelatine 
and can stabilize emulsions, even after being 
subjected to changes in temperature, salt 
concentration and pH. Fish skin, in particular 
from larger fish, provides gelatine as well as 
leather for use in clothing, shoes, handbags, 
wallets, belts and other items. Antifreeze proteins 
from polar fishes’ skin tissue can be used to 
reduce the damage caused by frozen storage of 
meat. Antifungal and antibacterial properties of 
the epidermis, epidermal mucus of different fish 
species, liver, intestine, stomach and gills of some 
fish species, and the blood and shell of some 
crustaceans can act as an immunological barrier. 
Beyond finfish, crustaceans and bivalves also 
offer numerous applications for their by-products, 
which not only increase the value of these 
products, but also address waste disposal 
issues caused by the slow natural degradation 
rate of their shells. Chitin, a polysaccharide 
extracted from crustacean shell waste, is a 
potential source of antimicrobial substances. 
Its derivative chitosan has shown a wide 
range of applications, notably in the fields of 
wastewater treatment, cosmetics, toiletries, food, 
beverages, agrochemicals and pharmaceuticals. 
Pigments such as astaxanthin and its esters, 
β
-carotene, lutein, astacene, canthaxanthin 
and zeaxanthin are also found in crustacean 
waste. Some of these have important medical 
and biomedical applications due to their high 
antioxidant effects and as vitamin A precursors. 
The shells of bivalves, such as mussels and 
oysters, can be turned into calcium carbonate 
or calcium oxide, two highly versatile chemical 
compounds with wide industrial applications. 
Other uses for shells include their transformation 
into cosmetics and traditional medicines (pearl 
powder), calcium supplement in animal feed 
(shell powder), handicrafts and jewellery.
Other marine organisms are the subject of 
extensive research because of their potential 
for the discovery of powerful new molecules. 
Anti-cancer drugs, in particular, have been 
developed from marine sponges, cyanobacteria 
and tunicates. Other applications include 
ziconotide, a powerful painkiller derived from the 
venom of cone snails, and vidarabine, an antiviral 
drug that was isolated from a marine sponge 
(Malve, 2016). While these chemical compounds 
are chemically synthesized, the culture of 
some sponge species for this purpose is also 
being investigated. 
Seaweeds and other aquatic plants have been 
used as food for centuries in Asia, and they are 
increasingly gaining attention in many countries 
elsewhere due to their perception as being an 
environmentally friendly food that is rich in 
nutrients, such as iodine, iron and vitamin A 
(Tanna and Mishra, 2019). Seaweeds can be 
used, generally in dried powder form, for feed 
additives, cosmetics (for example, the seaweed