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1.1 Introduction
1.1. World aquaculture
From 2000 to 2018, total world aquaculture production increased by 42%, reaching
an all-time high (FAO, 2020b). From 1995 to 2018, the trend of aquaculture fish
production by percentage of world total was increasing in Africa and the Americas,
and the trend was stable in Asia; however, the trend was decreasing in Europe
(FAO, 2020a). In 2018, the value of aquaculture production was 139.7 billion USD
and aquaculture employed 20.5 million people (FAO, 2020a). Aquaculture is the
fastest-growing livestock production sector (Garlock et al., 2020). Freshwater fish
aquaculture production increased by 131% between 2000 and 2018 (FAO, 2020b).
Most aquaculture production comes from Asian countries, dominated by China,
Indonesia and India (FAO, 2020b). Carps and tilapia are the dominant freshwater
species groups.

1.2. Nile tilapia Aquaculture
Nile tilapia is the most important commercial fish species in tropical freshwater
aquaculture, with an estimated global production of 4.8 million tons in 2018 (FAO,
2020a). Nile tilapia constitutes 8.3% of the total finfish produced in 2018, which
makes it the third most-produced finfish next to Grass carp (Ctenopharyngodon
idellus) (10.3%) and Silver carp (Hypophthalmichthys molitrix) (8.4%) (FAO, 2020a).
Global Nile tilapia production increased by 19.6 times in 2019 compared to 1990
(Figure 1.1) (FAO, 2021). Nile tilapia production in 2019 increased from about 201
thousand tons to 2.9 million tones in Asia, from about 4.7 thousand tons to 436
thousand tons in Latin America and from about 27 thousand tons to 1.26 million
tons compared to 1990 (Fig 1).

The feeding habit, high growth rate and disease tolerance of Nile tilapia have
helped the production of this species to become widespread. Tilapias are
herbivorous/omnivorous fish (El-Sayed, 2006), therefore, less wild fish is used in
tilapia feed than in carnivorous fish feed (Naylor et al., 2021); and feeding tilapia is
less costly than carnivorous fish. Nile tilapia is also hardy, resistant to disease and
tolerates poor water quality (Bhujel, 2014), and is farmed under diverse production
systems: extensive, semi-intensive, or intensive production systems. Extensive and
semi-intensive Nile tilapia farms are managed by smallholder farms, while the
intensive Nile tilapia farms are managed by big commercial companies.

Extensive production systems are characterized by the use of low stocking density,
no or limited use of supplementary feed or fertilization as Nile tilapia can rely on

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