Oreochromis niloticus (Nile tilapia): WelfareCheck|farm

Distribution

IUCN Red List status

least concern

Information

Authors: Jenny Volstorf, Caroline Marques Maia, João L. Saraiva
Version: C | 2.0 (2024-07-20)

Reviewer: Jenny Volstorf
Editor: Jenny Volstorf

Initial release: 2016-12-14
Version information:

Appearance: C
Last major update: 2024-07-20

Cite as: »Volstorf, Jenny, Caroline Marques Maia, and João L. Saraiva. 2024. Oreochromis niloticus (WelfareCheck | farm). In: fair-fish database, ed. fair-fish. World Wide Web electronic publication. First published 2016-12-14. Version C | 2.0. https://fair-fish-database.net.«

WelfareScore | farm

Oreochromis niloticus

LiPoCe

Criteria

Home range

Depth range

Migration

Reproduction

Aggregation

Aggression

Substrate

Stress

Malformations

Slaughter

Legend

Condensed assessment of the species' likelihood and potential for good fish welfare in aquaculture, based on ethological findings for 10 crucial criteria.

Li = Likelihood that the individuals of the species experience good welfare under minimal farming conditions
Po = Potential of the individuals of the species to experience good welfare under high-standard farming conditions
Ce = Certainty of our findings in Likelihood and Potential

WelfareScore = Sum of criteria scoring "High" (max. 10)

High

Medium

Low

Unclear

No findings

General remarks

Oreochromis niloticus originated in fresh waters of the Middle East as well as sub-Saharan Africa. It is one of the top 5 most frequently cultured species worldwide, mainly reared in Southeast Asia, China, and Africa. Due to its fast growth, it can reach market size in 5-6 months. Its rearing does not come without a toll on the individuals, though. Because maturity sets in early as well, farmers in intensive rearing administer hormones through the feed that renders individuals all male, or genetic engineering results in all-male populations. This prevents unwanted reproduction and the growth deficiencies that come with it. Also, it favours males which grow up to 50% faster than females.

The two most frequently used culture systems are ponds and cages of which earthen ponds, especially irrigation ponds or reservoirs, overlap more with the natural needs of space, density, and substrate than cages. Shelters and shading may also be applied artifically, though. IND are allowed to spawn naturally, i.e., without manipulation and stripping, but there seems to be a trend towards hormonal induction to synchronise spawning or avoid injuries by aggressive SPAWNERS. Aggression is an issue in other age classes as well and does not seem to be avoidable completely; one recommended method - to size grade - is stressful itself. Other husbandry practices like handling and transport impose stress, too, which may be reduced but not avoided. Electrical stunning followed by exsanguination, evisceration, or filleting is availabla but at risk of failing if not executed correctly.

Note: We used some older sources that referred to O. niloticus as Tilapia nilotica 1 2 or Sarotherodon niloticus 3 4 5 6, as was common at the time.

1 Home range

Many species traverse in a limited horizontal space (even if just for a certain period of time per year); the home range may be described as a species' understanding of its environment (i.e., its cognitive map) for the most important resources it needs access to.

What is the probability of providing the species' whole home range in captivity?

It is unclear for minimal and high-standard farming conditions, given we mainly found data from farms. Our conclusion is based on a medium amount of evidence, as further research is needed on home range in the wild.

Likelihood score-li

Potential

Certainty

Eggs: does not apply.

LARVAE and FRY:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9). Mouthbreeding females release FRY 1 after yolk sac absorption, maximum 13.5 mm TOTAL LENGTH 10, guard over clouds of FRY 1, external feeding from 15 mm on 6. After female is gone, no data found yet on home range.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14 to hatch in incubation jars 12 or 1-10 m³ nursery tanks 11 or 1-2 m² 15, 9-40 m² (3 x 3 m, 8 x 2.5 m, 8 x 5 m) hapas in nursery ponds or directly in 100-500 m² nursery ponds 11, 100-1,000 m² 16 or 200 m³ tanks 17. From incubation jars to pre-growing ponds: 30 m² (3 x 10 m) 12. FINGERLINGS ponds: 200 m² 18. Pre-growing cages: 1 m² (1 x 1 m) 19, 4 m² (2 x 2 m) 20.
LAB: does not apply.

JUVENILES:

WILD: no data found yet.
FARM: ponds: 100-10,000 m² 21, 100 m² 22, minimum 300 m³ 23, 660-6,600 m² 24, 5,000-14,000 m² 16, ponds for polyculture with C. gariepinus: 150 m² 25, irrigation ponds and reservoirs: <670,000 m² 24. Cages: 1-900 m² (1 x 1 m, 30 x 30 m) 21, 1 m² 26, 2.3 m² (1.5 x 1.5 m) 16, 3.1 m² 27, 4 m² (2 x 2 m) 28 29, 6 m² (3 x 2 m) 30, 9-18 m² (3 x 3 m, 5-6 x 3 m) 11, 25 m² (5 x 5 m) 24. Concrete tanks: 3.8 m² (2.5 x 1.5 m) 31. Tanks and raceways: 10-1,000 m³, circular, rectangular, square, oval 32, tanks in RAS: 1.5 m³ 33, tanks: 15 m² 34. Paddy fields 24.
LAB: does not apply.

ADULTS:

WILD: no data found yet.
FARM: ➝ JUVENILES.
LAB: does not apply.

SPAWNERS:

WILD: nests may be >1 m ∅ 1. Non-native habitat: bowers with pit of 0.4-1.9 m ∅ 35, nests of range 0.05-1 m ∅, mean 0.4-0.6 m ∅ 36. Mouthbreeding females stay inactive until FRY require external feed, then move to shallow areas 37 and guard FRY 1, external feeding from 15 mm on 6.
FARM: ponds: pre-spawning (sexes separated): 200 m², then concrete (sexes combined, in hothouse): 24 m² (4 x 6 m) 14, concrete: 30 m² (3 x 10 m) 12, earthen ponds: 750 m² 15. Cages: 4.5 m² (3 x 1.5 m) 19. Conditioning and production tanks: 24 m² (3 x 8 m) 38, >30 m² 11, 200 m³ 17. Higher number of eggs in 4 m² (2 x 2 m) concrete tanks than 4 m² (2 x 2 m) hapa nets 39. Hapa nets: 6 m² (3 x 2 m) 40, 16 m² (8 x 2 m) 13.
LAB: does not apply.

2 Depth range

Given the availability of resources (food, shelter) or the need to avoid predators, species spend their time within a certain depth range.

What is the probability of providing the species' whole depth range in captivity?

It is low for minimal farming conditions, as ponds, cages, tanks, and hapas do not cover the whole range in the wild (except for SPAWNERS). It is medium for high-standard farming conditions, as the mentioned systems at least overlap with the range in the wild. Our conclusion is based on a high amount of evidence unless farm studies show that O. niloticus is well under lower depths as in the wild.

Likelihood score-li

Potential

Certainty

Eggs:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9).
FARM: mouthbred 11 or collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14 to hatch in jars and trays 11.
LAB: does not apply.

LARVAE and FRY:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9). Mouthbreeding females move to shallow areas 1 (non-native habitat: mouthbreeding females in 0-4 m littoral 8), release FRY 1 after yolk sac absorption, maximum 13.5 mm TOTAL LENGTH 10, guard over clouds of FRY 1, external feeding from 15 mm on 6. After female is gone, abundant in littoral <4 m 4, at 0.05-0.3 m during the day, deeper at night 6.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. Ponds: 0.5-1.4 m 16. Hapas in nursery ponds: 0.8-1.5 m 11, 1-2 m 15, increasing pond and hapa depth increases hatching rate and improves larval development through providing lower temperatures 11. FINGERLINGS ponds (until market size and beyond): higher growth and lower mortality at 3 m than 0.5, 1, or 2 m 18. Pre-growing cages: 1 m 19, 2 m 20.
LAB: does not apply.

JUVENILES:

WILD: caught at 0-4 m 3, ≤10 m, seldomly at 10-30 m 5; non-native habitat: caught at 0-4 m 8, ≤10 m 42, 0-15 m 43, at 12-16 m during day and night 44, some ≤20 m 43. Caught in lakes of 0.8-6.4 m 7, 2-4.9 m (non-native habitat: 45), 20 m (non-native habitat: 46-47) with unclear depth range use. Seldomly in open water and deeper depths at low turbidity 5, but also on the bottom in thick deposit of organic mud (non-native habitat: 44). Non-native habitat: moving between littoral with vegetation close to shore 8 and deeper off shore with sandy or rocky bottom 42; detritus in stomach indicates bottom grazing 45 48 49 50.
FARM: ponds: 0.5-3 m 21, 0.8 m at shallow end, 1.2 m at deep end 51 23, deeper (1-1.5) if entirely dependent on rain water 23, 1 m 22, 1 m at shallow end, 1.5-2 m at drainage end 11, 1.1-1.8 m 16, 1.5-3.5 m 24, ponds for polyculture with Clarias gariepinus: 1.3 m 25, irrigation ponds and reservoirs: >10 m 24. FINGERLINGS ponds (until market size and beyond): higher growth and lower mortality at 3 m than 0.5, 1, or 2 m 18. Cages: 0.8 m 29, 1 m 27 26, 1-3 m 21, 1.5 m 28 30 16, 3 m 11, 4-6 m 24. Concrete tanks: 1.1 m 31, tanks with bottom substrate: 1.2 m 34.
LAB: does not apply.

ADULTS:

WILD: ➝ JUVENILES.
FARM: ➝ JUVENILES.
LAB: does not apply.

SPAWNERS:

WILD: nests in 0.6-1.2 m 1. Non-native habitat: bowers with pit of 0.4-1.4 m depth, rim height of 0.01-0.5 m 35, nesting depth 0.8-1.4 m 36, mouthbreeding females in 0-4 m littoral 8.
FARM: ponds: pre-spawning (sexes separated): 1.2 m, then concrete (sexes combined, in hothouse): 1.5 m 14, concrete: 1 m, water level 0.7 m 12, earthen ponds: 0.5 m 15. FINGERLINGS ponds (until market size and beyond): breeding observed at 1, 2, and 3 m, but not at 0.5 m 18. Cages: 1 m 19. Hapa nets: 1 m 13 40, 1 m water level 39. Conditioning and production tanks: 0.8-0.9 m 11, 1 m 38, 1 m water level 39, deep tanks (1-2 m) increase reproductive performance 11.
LAB: does not apply.

3 Migration

Some species undergo seasonal changes of environments for different purposes (feeding, spawning, etc.), and to move there, they migrate for more or less extensive distances.

What is the probability of providing farming conditions that are compatible with the migrating or habitat-changing behaviour of the species?

It is low for minimal farming conditions, as the species undertakes more or less extensive migrations, and we cannot be sure that providing each age class with their respective environmental conditions will satisfy their urge to migrate or whether they need to experience the transition. It is medium for high-standard farming conditions, as the space range in captivity overlaps with the migration distance. Our conclusion is based on a medium amount of evidence, as further research is needed on specific migration distances in the wild.

Likelihood score-li

Potential

Certainty

Possibly POTAMODROMOUS 6. EURYHALINE, but grows best in fresh water 21.

Eggs: does not apply.

LARVAE and FRY:

WILD: maternally mouthbred in fresh7 (non-native habitat: 8) or brackish water 1 3 (non-native habitat: 9). Afterwards, abundant inshore 4, but present in all parts of the lake 6. Movement from one lake side to the opposite (lake breadth: 13-44 km), probably assisted by lake currents 6.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. For details of (freshwater) holding systems ➝ F1 and F2.
LAB: increasing morphological changes (yolk sac surface, lateral skeletal muscle, trunk area) with increasing salinity (0, 2, 4, 6 ppt) in newly-hatched LARVAE 52.

JUVENILES:

WILD: mainly in inshore waters of one (brackish) lake, sometimes moving offshore 1, in other lake: mostly open water 1, probably disperse after nursery phase into open waters 6. Non-native habitat: feeding at lake edges, in lagoons in estuaries of inflowing rivers, living off-shore in lakes 2, moving between littoral with vegetation close to shore and deeper off shore with sandy or rocky bottom 42.
FARM: for details of (freshwater) holding systems ➝ F1 and F2. May be transferred to <15 ppt in shallow seas, on beaches, in seaside ponds 24. Tanks: 2.7-4 g/L salinity 34.
LAB: no data found yet.

ADULTS:

WILD: ➝ JUVENILES.
FARM: ➝ JUVENILES.
LAB: no data found yet.

SPAWNERS:

WILD: fresh (non-native habitat: 8) or brackish water 1 3. If not already inshore, move there from open water to breed 1 6. Mouthbreeding females stay inactive until FRY require external feed, then move to shallow areas 37.
FARM: for details of (freshwater) holding systems ➝ F1 and F2.
LAB: no data found yet.

4 Reproduction

A species reproduces at a certain age, season, and sex ratio and possibly involving courtship rituals.

What is the probability of the species reproducing naturally in captivity without manipulation of these circumstances?

It is low for minimal farming conditions, as the species is manipulated (hormonal manipulation, eggs taken from female’s mouth, in the lab also stripping) and may be taken from the wild. It is high for high-standard farming conditions, as natural breeding (without manipulation) with farm-reared IND is possible and verified for the farming context. Our conclusion is based on a medium amount of evidence, as further research is needed on reproduction behaviour in the wild.

Likelihood score-li

Potential

Certainty

Eggs: does not apply.

LARVAE and FRY: does not apply.

JUVENILES: does not apply.

ADULTS: does not apply.

SPAWNERS:

WILD: mature in first year of life (non-native habitat: 8), spawn throughout the year 6 (non-native habitat: 8) every 30-90 days (non-native habitat: 9) in batches (non-native habitat: 53). Mouthbreeder: female takes eggs in mouth after fertilisation 1 6 7 (non-native habitat: 8 9) until after yolk sac absorption, maximum 13.5 mm TOTAL LENGTH 10, and guards them 1, external feeding from 15 mm on 6. For nest building ➝ F3.
FARM: in Africa, IND may be taken from the wild 11. Mature at 5-6 months 11, used for spawning until 1.5-2 years 11 or at 2-4 years old 54, spawn every 21-90 days 39 19 at sex ratio 1:2 15 13 11, 1:3 19 12 14 11 40, or 1:4-1:10 male:female (tendency of higher number of eggs at 1:4) 39. PHOTOPERIOD and temperature adjustment to induce off-season spawning 38 which we do not consider manipulation. Hormonal manipulation for spawning induction to guarantee exact time of spawning 54. Male and female kept separately 14 54 11 for short time until ready to spawn which increases reproductive efficiency 11; 3 weeks after spawning, reconditioning period of 2 weeks during which IND are separated 13. Higher absolute number of eggs the heavier the female 15. Eggs are either left to hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14, otherwise reduced reproductive potential and increased interspawning interval 11.
LAB: male courted female 55 56 57. Spawning only when visual or visual and chemical communication between male and female possible 57. Female released eggs in batches, took them immediately up in mouth 55. Males spawned 2-4 times/day, the higher the spawning frequency, the fewer eggs fertilised 58. The higher the female's age, weight, and length, the higher the total fecundity (number of eggs per spawn), the older the female, the higher the relative fecundity (number of eggs per kg weight) 58. Higher proportion of mouthbreeding under blue than under white light 59. Hormonal manipulation to induce spawning in females 60 61 54 62, plus artificial fertilisation (females 54 or both sexes stripped 60 62) to synchronise maturation for breeding programmes 60, to circumvent male aggression (injuries, mortality) during SPAWNERS pairings 62.

5 Aggregation

Species differ in the way they co-exist with conspecifics or other species from being solitary to aggregating unstructured, casually roaming in shoals or closely coordinating in schools of varying densities.

What is the probability of providing farming conditions that are compatible with the aggregation behaviour of the species?

It is low for minimal farming conditions, as densities in ponds, cages, tanks, and hapas go beyond the smallest density in the wild. It is medium for high-standard farming conditions, as densities in other ponds at least overlap with the density range in the wild. Our conclusion is based on a high amount of evidence, unless farm studies show that O. niloticus is well under higher densities as in the wild.

Likelihood score-li

Potential

Certainty

Eggs: does not apply.

LARVAE and FRY:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9). Mouthbreeding females release FRY 1 after yolk sac absorption, maximum 13.5 mm TOTAL LENGTH 10, guard over clouds of FRY 1, external feeding from 15 mm on 6. After female is gone, live in shoals 1 6 or schools (non-native habitat: 63). Estimated density in bed of Potamogeton pectinatus of IND 16-126 mm TOTAL LENGTH: 3.1 IND/m² or 0.01 kg/m² 4. Non-native habitat: at 10-30 mm TOTAL LENGTH: 12-30 IND/m² 8.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. FRY: stocking in FINGERLINGS ponds: 10 IND/m² 11, nursery ponds: 100-200 IND/m² 11, 500 IND/m³ (concrete) 14, 1,000 IND/m² 16. Incubation systems: 5 IND/L, hapas in earthen ponds: 1,000-2,000 IND/m² 11. Higher growth in hapa nets with 250 IND/m² than hapa nets with 1,000 IND/m² and concrete tanks with 1,000 IND/m² 64. Cages: survival >75% at 1,000-3,000 IND/m³ for pre-growing IND to 2 months, decreasing survival at densities beyond that 19, 800 IND/m² for pre-growing 2 months old IND to 5 months 19, higher growth of monosex male FINGERLINGS at 400 IND/m² than 500 or 600 IND/m² 20.
LAB: no data found yet.

JUVENILES:

WILD: shoal when in open water 1. Estimated density in bed of Potamogeton pectinatus of IND 16-126 mm TOTAL LENGTH: 3.1 IND/m² or 0.01 kg/m² 4, estimated density from bottom trawls: 0.00003 kg/m² 5. Non-native habitat: 0.001-0.01 IND/m² given type of vegetation 8.
FARM: ponds: extensive: 1-2 IND/m² 21 (also for IND to become SPAWNERS) 11, semi-intensive: 1-2 IND/m² (also for IND to become SPAWNERS) 11, 3-4 IND/m² 21, intensive: 3-3.8 IND/m², in deep ponds with aeration 3.8-4.5 IND/m², brackish water ponds 4.5-7.5 IND/m², 5 IND/m² 11, 5-10 IND/m² 21, 8 IND/m² 65, 10-30 IND/m² 16, higher growth at 1 and 3 IND/m² than 5 IND/m² 22, irrigation ponds and reservoirs: 0.8-1.5 IND/m², at times with added Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Ctenopharyngodon idella, or Carassius carassius 24, polyculture possible with Penaeus vannamei in brackish ponds of overall density of 30-60 IND/m² 24. Ponds: higher growth and survival under 3:1 polyculture with Clarias gariepinus (intentionally stocked later to avoid preying on O. niloticus), specifically under 3 IND/m² than 6 or 9 IND/m² 25. Cages: 10-15 IND/m³, up to 50-200 IND/m³ 21, 20-50 IND/m³, 40-50 IND/m³ with good water quality and cooler water, otherwise 20 IND/m³ 11, 50 IND/m³ 26, 142-500 IND/m³ 66, 267 IND/m² 16. Cages: higher growth at 100 than 150 or 200 IND/m³ 27. Cages: higher growth and more uniform sizes during 41 days at 200 than 500, 625, or 750 IND/m² making stressful size selection redundant and taking shorter to reach 800 g market size than medium-size selected IND at 150, 200, 225 IND/m² 28, higher growth at 375 than 525 and 675 IND/m² 30, higher growth and lower cortisol of genetically improved strain at 75 than 113 and 150 IND/m² 29. Concrete tank RAS and raceways: form shoal at 19.4 IND/m² 67, 10-50 IND/m² 11, no difference in growth between 16, 32, 42.6 IND/m² 31. Tanks in biofloc system: lower survival and water quality at 45 than 15 or 30 IND/m³ 65. Tanks: 2 IND/m² in monoculture, 0.5-2 IND/m² in a polyculture with Penaeus vannamei of overall density of 4.5-11 IND/m² 34. Paddy fields: 0.5-0.6 IND/m² 24.
LAB: decreasing aggression with increasing density 68. Higher stress in groups of 10 IND than in singly-held IND or pairs, lower growth in groups of 5 or 10 IND, probably indicating crowding stress 69. 12-day old IND built shoal of 10-100 IND, 2-months-old IND built shoal of 27 IND 70. Higher growth and more aggressive behaviour at 100 and 200 IND/m³ than 400 IND/m³, even more growth but fewer aggressions (still keeping the difference between densities) when fed oregano essential oils at 1.0 or 2.0 mL/kg diet, higher frequency of “comfort behaviour” (chafing, resting, surfacing, elimination) at 100 than 200 or 400 IND/m³, no effect on schooling, increasing cortisol levels with increasing density 71. Tendency of higher growth at 0.6 than 1.2 kg/m³ in groups of 10 IND, unless high-density IND provided with tactile stimulation through vertical sticks with silicone bristles (although highest growth at low density plus stimulation) 72.

ADULTS:

WILD: shoal when in open water 1. Non-native habitat: 0.001-0.01 IND/m² given type of vegetation 8.
FARM: ➝ JUVENILES.
LAB: no data found yet.

SPAWNERS:

WILD: spotted once: round shoals of several 100 IND with 3 m ∅, possibly in connection with breeding habit 1. Non-native habitat: bowers distributed in pond at 0.01-0.02 bowers/m² 35, nests aggregated in reservoir at 0.2-0.6 nests/m² (the higher the turbidity the higher the nest density) 36. Mouthbreeding females form small groups until FRY require external feed, then separate to care for FRY individually 37.
FARM: higher frequency of spawning when stocked in compartments than in groups 11. Increasing aggression with increasing density 11. Ponds: for IND to become SPAWNERS: extensive: 1-2 IND/m² 11, semi-intensive: 1-2 IND/m² 11; pre-spawning ponds: 5 females/m² 14, optimally 4-6 IND/m² 11. Cages: 4 IND/m² 19. Conditioning and production tanks: 7-14 IND/m² 11, concrete tanks: increasing growth and number of eggs with decreasing stocking density (2.9, 3.2, 3.5 IND/m²) 38. Concrete tanks and hapa nets: tendency of highest number of eggs at 5 IND/m² than 8 or 11 IND/m² 39.
LAB: no data found yet.

6 Aggression

There is a range of adverse reactions in species, spanning from being relatively indifferent towards others to defending valuable resources (e.g., food, territory, mates) to actively attacking opponents.

What is the probability of the species being non-aggressive and non-territorial in captivity?

It is low for minimal farming conditions, as the species is aggressive – even cannibalistic – in almost all age classes. It is medium for high-standard farming conditions, as a) ways to reduce (but not avoid) aggression (size homogeneity, density) are verified for the farming context, although there are contradictory findings on whether increasing or decreasing density is best and b) more ways to reduce aggression (adding oregano oil or tryptophan to the diet, tactile stimulation, low light intensity) need to be verified for the farming context. Our conclusion is based on a medium amount of evidence.

Likelihood score-li

Potential

Certainty

Eggs: does not apply.

LARVAE and FRY:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9). Mouthbreeding females release FRY 1 after yolk sac absorption, maximum 13.5 mm TOTAL LENGTH 10, guard over clouds of FRY 1, external feeding from 15 mm on 6. After female is gone, live in shoals 1 6 or schools (non-native habitat: 63), thus probably no aggression.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. Leaving LARVAE to develop in breeding pond and scooping FRY may be difficult to get all IND out and because of cannibalism 24, cannibalism and predation by larger IND may be prevented by avoiding high stocking densities, by regular size grading, or by using double hapa which separates breeders from FRY 11. Stocking FRY of same age prevented cannibalism 19.
LAB: no data found yet.

JUVENILES:

WILD: no data found yet.
FARM: decreasing aggression with increasing density 73. No aggression reported in polyculture with Clarias gariepinus 25, Penaeus vannamei 34.
LAB: decreasing aggression with increasing density 68. Established linear hierarachy in groups of 4 males, dominant IND chased and attacked subordinate 74. Dominant IND displayed biting, ramming, cornering, chasing of subordinate IND and biting, ramming, mouth-fighting of other dominant IND in mixed-sex groups of 5, 10, or 15 IND 75, dominant IND chased and attacked subordinate 76 in mixed-sex pairs 77. Enrichment with river pebbles and plastic kelp increased number of fights and bites in pairs of IND compared to control 76. More aggressive behaviour at 100 and 200 IND/m³ than 400 IND/m³, fewer aggressions (but keeping the difference between densities) when fed oregano essential oils at 1.0 or 2.0 mL/kg diet 71. Lower number of bites against mirror in group of 10 IND when fed 2.6% tryptophan in diet than 1.3 than 0.3% 78, fewer confrontations when fed 2.6% tryptophan in diet than when provided shelters (PVC pipes) or artificial water hyacinth (frayed nylon rope) or control 79. Less aggressive behaviour and higher weight gain in groups of 4 IND when provided with tactile stimulation through vertical sticks with silicone bristles 80.

ADULTS:

WILD: no data found yet.
FARM: ➝ JUVENILES.
LAB: in seven of 10 groups of two males 81, one male became dominant 82 81 56, chased and attacked subordinate IND 82. In six of seven groups of two males 81, larger male became resident over smaller male intruder 81 83, chased and attacked subordinate IND 81. Established linear hierarchy in groups of 3 females 84, 3 males 85, dominant IND chased and attacked subordinate 84 85. Tendency of fewer aggressions under low (280.8 lux) than high (1,394.1 lux) light intensity in group of 3 IND 85.

SPAWNERS:

WILD: no data found yet.
FARM: important to select IND of similar size, otherwise males 30-40% larger than females become very aggressive, nipping at females until the point of mortality 11. Increasing aggression with increasing density 11.
LAB: nesting male attacked other male 55. Established linear hierarchy in groups of 2 males:3 females, dominant males built nests and defended them against males and females 86. Nesting males released pulses (sounds) when another male entered the territory 87. Spawning only in dominant males in groups of 2 males and 3 females 86. Hormonal manipulation for spawning induction in females plus artificial fertilisation (both sexes stripped) to circumvent male aggression (injuries, mortality) during SPAWNERS pairings 62.

7 Substrate

Depending on where in the water column the species lives, it differs in interacting with or relying on various substrates for feeding or covering purposes (e.g., plants, rocks and stones, sand and mud, turbidity).

What is the probability of providing the species' substrate and shelter needs in captivity?

It is low for minimal farming conditions, as almost all age classes of the species use substrate, but some ponds, cages, tanks, and hapas are devoid of it. It is high for high-standard farming conditions given a) eggs are left in female’s mouth, b) earthen ponds for FRY to ADULTS which are not replaced by concrete bottom, and given b) natural reproduction with spawning substrate in ponds for SPAWNERS. Our conclusion is based on a medium amount of evidence, as further research is needed to determine whether shading and aerial protection nets suffice as replacements of structurally complex wetlands and macrophytes.

Likelihood score-li

Potential

Certainty

Eggs:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9).
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. Ponds: shading increases hatching rate through lower temperatures 11. For details of holding systems ➝ F1 and F2.
LAB: no data found yet.

LARVAE and FRY:

WILD: maternally mouthbred 1 7 (non-native habitat: 2 8 9), afterwards over sand (non-native habitat: 8) along shores or in muddy lagoons 1, in well-sheltered gulfs or bays 4, among inundated vegetation 6, seek shelter of macrophytes at night 6.
FARM: hatch in female’s mouth in breeding ponds (females leave when FRY reach 9-10 mm TOTAL LENGTH) 11 or are collected from female’s mouth 12 11 every 5-7 days 13 11, 10 days 14. Ponds: rocks or tarpaulin at the bottom (with or without aerial protection nets) 16, shading improves larval development through lower temperatures 11. For details of holding systems ➝ F1 and F2.
LAB: no data found yet.

JUVENILES:

WILD: live along sheltered sandy beaches 1, in well-sheltered gulfs or bays 4, over sand and mud 7 (non-native habitat: 8 9 88). Seldomly in open water and deeper depths at low turbidity 5, but also on the bottom in thick deposit of organic mud (non-native habitat: 44). Non-native habitat: moving between littoral with vegetation close to shore 8 and deeper off shore with sandy or rocky bottom 42; detritus in stomach indicates bottom grazing 45 48 49 50; seek shelter from predatory Lates niloticus in complex wetlands 89-48 90-48 91-48 92-48; Secchi disc depth 0.2 m 45, 0.7-0.8 45 48. Higher abundance at lower transparency and higher abundance in structurally complex wetlands compared to open water might indicate taking shelter from Lates niloticus 48.
FARM: ponds: higher growth with added bamboo poles where periphyton grew than without substrate 51, minimal silt on bottom 24, substrate or rocks at the bottom, very turbid water 16. Cages: turbidity: Secchi disc 0.7-1.1 m 27. For details of holding systems ➝ F1 and F2.
LAB: enrichment with river pebbles and plastic kelp increased number of fights and bites in pairs of IND compared to control 76. Higher growth and lower scratching behaviour (stereotypical behaviour) when provided shelter (PVC pipes) or artificial water hyacinth (frayed nylon rope) than 2.6% tryptophan in diet (but no growth difference to control), preferred aquarium sections with shelters and artificial plant, lower ventilatory frequency with artificial plant 79. Longer time freezing during novel object test after 7 weeks isolation in barren than enriched aquaria (substrate) and than in 4 weeks isolation indicating fear, longer time exploring novel object after habituation in enriched than barren aquaria 93. Higher frequency of freezing, lower frequency of hovering and chasing in tanks 50% covered than open tanks, higher cortisol levels in 50% than 100% cover indicating disadvantages of 50% cover 94. Less aggressive behaviour and higher weight gain in groups of 4 IND when provided with tactile stimulation through vertical sticks with silicone bristles 80. Tendency of higher growth at 0.6 than 1.2 kg/m³ in groups of 10 IND, unless high-density IND provided with tactile stimulation through vertical sticks with silicone bristles (although highest growth at low density plus stimulation) 72.

ADULTS:

WILD: ➝ JUVENILES.
FARM: ponds: minimal silt on bottom 24. For details of holding systems ➝ F1 and F2.
LAB: males preferred aquaria with shelter over those without and aquaria with gravel over those without 95, in aquaria with shelter and gravel and bare bottom compartment, males preferred the gravel compartment on the first day and were indifferent between shelter, gravel, and bare bottom compartments on the following days 95.

SPAWNERS:

WILD: male builds nest in sand or inshore reed areas 1, in sandy sheltered conditions 6. Non-native habitat: bowers in sediment of mud and fine sand or silt and fine sand with 0-9.2 m distance to vegetation 35, nests in medium and fine sand at turbidity 3.1-11.3 NTU (the higher the turbidity the higher the nest density), sometimes covered by vegetation 36, mouthbreeding females in littoral with vegetation 8.
FARM: ponds: decreasing dissolved oxygen and temperature with increasing shading over hapa nets (no shading, shading on top, half, complete), higher absolute fecundity, spawning rate, number FRY under shading than without 40. Cages with solid base and 25 cm sand layer 19. Tanks: artificial spawning shelters improve reproductive efficiency 11. Hapa nets on tank bottom with mud 13. For details of holding systems ➝ F1 and F2.
LAB: males and females threw sand and cleaned the nest before spawning 55. Tanks: higher number of sexually active females when artificial reef installed than bare bottom, sandy bottom in between 96. Males and females built nests in aquaria with gravel layer 57. Males preferred aquaria with sand over aquaria with sand-shell mixture, did not nest in barren aquaria 97. Males moved larger mass for nest building and built wider nests under blue than white light 59. The higher the investment in nest building (weight of gravel displaced per body weight), the higher the spawning frequency and the more frequent female nest visits, but overall spawning frequency and latency independent of substrate indicating behavioural plasticity to reproduce under all kinds of circumstances 86.

8 Stress

Farming involves subjecting the species to diverse procedures (e.g., handling, air exposure, short-term confinement, short-term crowding, transport), sudden parameter changes or repeated disturbances (e.g., husbandry, size-grading).

What is the probability of the species not being stressed?

It is low for minimal farming conditions, as the species is stressed (water quality, handling, confinement, crowding, transport). It is medium for high-standard farming conditions, as some ways to reduce (but not avoid) stress are verified for the farming context. Our conclusion is based on a high amount of evidence, as it seems clear that stress cannot be avoided.

Likelihood score-li

Potential

Certainty

Eggs:

WILD: no data found yet.
FARM: stressed (to the point of mortality) when exposed to ≤17 °C or 39.5 °C directly after fertilisation, best hatching at 28 °C 58.
LAB: eggs hatched at a higher rate survived with higher probability in round-bottom than conical hatching jars, suggesting mechanical stress through friction between eggs and between eggs and container as major influence 58.

LARVAE and FRY:

WILD: no data found yet.
FARM: FRY: higher oxygen consumption and lower short-term growth after 6 h transport in polyethylene bags over bad road than over good road which might be improved through styrofoam pack absorbers 98. Stressed by handling in direct sunlight at noon, rather prefer handling in mornings or evenings and under shade 11, stressed by net material that will cause injuries, slightly larger mesh size that will entangle the gills, abrupt movements, dropping on the floor 11.
LAB: stressed by suppression of aeration (hypoxia), which may be reduced by the administration of sulfated polysaccharides (0.05-0.1 mg/g) in the feed (also improving growth) 17.

JUVENILES:

WILD: no data found yet.
FARM: stressed (to the point of mortality) by size grading 28. Cages: higher growth and lower cortisol of genetically improved strain at 75 than 113 and 150 IND/m² 29. Tanks in RAS: higher growth at 2,000 lux than 1,000 or 3,000 lux, lower cortisol at 18 and 24 h than 12 h PHOTOPERIOD 33. Stressed by transport for 4 h in plastic bags with oxygen at density 4 IND/L, even more so at 10 IND/L 99.
LAB: higher stress in groups of 10 than in singly-held IND or pairs, indicating crowding stress 69. Stressed by chasing with net for 60 s 69 100. Stressed by handling 101 102 which could not be reduced with eugenol but made handling IND easier 101, anaesthetisation with clove oil (250 m/L) more successive, but induced some stress itself 102. Stressed (to the point of mortality) under 24 h or 0 h PHOTOPERIOD compared to 12 h PHOTOPERIOD 103. No difference in ventilatory frequency under white, blue, or yellow light when tested individually 104. Higher cortisol levels in IND exposed to water from stressed conspecifics than in control group 100. Individual differences in boldness: males with more number of returns to and more time spent in former confinement area also displayed lower cortisol levels after emerged netting, faster food intake recovery in a novel environment, less neophobia towards a novel object, and more body displacements in an emerged net, indicating boldness 105; males escaping faster from a confinement situation also returned to the area the confinement took place slower, spent less time there, and displayed higher cortisol levels, indicating stress 105. Higher frequency of “comfort behaviour” (chafing, resting, surfacing, elimination) at 100 than 200 or 400 IND/m³, no effect on schooling, increasing cortisol levels with increasing density 71. Lower ventilatory frequency when provided with artificial water hyacinth (frayed nylon rope) than shelters (PVC pipes), 2.6% tryptophan in diet, or control 79. Higher cortisol levels in 50% than 100% cover indicating disadvantage of 50% cover 94.

ADULTS:

WILD: no data found yet.
FARM: no data found yet.
LAB: stressed by netting, even more so if done repeatedly 106. Probably stressed by food competition in group of 15 IND 107. No difference in growth under blue, violet, red, green, or yellow light when tested individually, but weight differences in groups of 4 IND except for yellow light with highest variation under red light 108. Stressed by confinement 109 plus white or green but not blue light 110 or more under white than blue light, yellow light in between 104. Auditory threshold 10 dB higher than control when exposed to noise for 28 days at 800 Hz 111. Stressed by tailfin clipping 112. Single IND stressed by pairing with dominant IND 113 or larger resident (increase in ventilatory frequency), confinement (either increase or decrease of ventilatory frequency), electric shock (either increase of decrease of ventilatory frequency) where the difference in ventilatory frequency reactions might indicate having to take a deeper look at this indicator, as it could also be the amplitude that is increasing 83.

SPAWNERS:

WILD: no data found yet.
FARM: extraction of eggs from mouth of female by lowering pond water level from 0.7 to 0.2 m, scooping out and placing on plate, which frightened female so that she released eggs 12.
LAB: no data found yet.

9 Malformations

Deformities that – in contrast to diseases – are commonly irreversible may indicate sub-optimal rearing conditions (e.g., mechanical stress during hatching and rearing, environmental factors unless mentioned in crit. 3, aquatic pollutants, nutritional deficiencies) or a general incompatibility of the species with being farmed.

What is the probability of the species being malformed rarely?

It is high for minimal and high-standard farming conditions, as malformation rates do not exceed 10%. Our conclusion is based on a medium amount of evidence, as further research is needed.

Likelihood score-li

Potential

Certainty

Eggs:

WILD: no data found yet.
FARM: no data found yet.
LAB: no data found yet.

LARVAE and FRY:

WILD: no data found yet.
FARM: deformities in 3.3-8.3% of IND, with no effect of amount of inbreeding 114.
LAB: increasing morphological changes (yolk sac surface, lateral skeletal muscle, trunk area) with increasing salinity (0, 2, 4, 6 ppt) in newly-hatched LARVAE 52.

JUVENILES:

WILD: no data found yet.
FARM: skeletal deformities (lateral projections of the mandible, 'parrot-like head', scoliosis, kyphosis, lordosis, fusion of dorsal and anal fins) in 1.6-2.7% 115.
LAB: no data found yet.

ADULTS:

WILD: no data found yet.
FARM: ➝ JUVENILES.
LAB: no data found yet.

SPAWNERS:

WILD: no data found yet.
FARM: no data found yet.
LAB: no data found yet.

10 Slaughter

The cornerstone for a humane treatment is that slaughter a) immediately follows stunning (i.e., while the individual is unconscious), b) happens according to a clear and reproducible set of instructions verified under farming conditions, and c) avoids pain, suffering, and distress.

What is the probability of the species being slaughtered according to a humane slaughter protocol?

It is low for minimal farming conditions. It is high for high-standard farming conditions, as electrical stunning, followed by exsanguination, evisceration, or filleting, induces unconsciousness fast (if done correctly), kills while still unconscious, and is verified for the farming context. Our conclusion is based on a medium amount of evidence, as further research is needed to determine how often electrical stunning fails in the farming context.

Likelihood score-li

Potential

Certainty

Eggs: does not apply.

LARVAE and FRY: does not apply.

JUVENILES:

WILD: does not apply.
FARM: minimal slaughter method: sold alive 24 at local markets without ice 23 to postpone rigor mortis 11, so probably asphyxia; placing on ice or in refrigerator 23 11, so probably asphyxia. Electrical stunner used in an inappropriate way and without amperage control, not followed by slaughter step resulting in IND receiving improper electrical shocks and being peeled and filleted alive 16. High-standard slaughter method: rapid killing (unspecified) followed by gutting or filleting 23, in-water electrical stunning followed by bleeding 116.
LAB: no data found yet.

ADULTS:

WILD: does not apply.
FARM: probably ➝ JUVENILES, but sources do not specify the age class 117.
LAB: electrical stunning 118. Fastest time to loss of vital signs under electrical stunning than immersion in 50:50 ice water mixture or CO2 narcosis, higher cortisol levels under 50:50 ice water mixture although still considered low stress 119. Higher number of IND losing consciousness without recovery after lateral than frontal spiking with Ikigun 120. Electrical stunning in water did not render IND unconscious 120. Faster onset of unconsciousness by mechanical spiking with captive bolt pistol than anaesthesia with 2-phenoxyethanol, essential oils (Ocimum americanum or Lippia alba), or hypothermia in 1:2 water:ice mixture, but a) IND did not show aversion to the essential oils rendering them nonetheless interesting for stunning, b) hypothermia caused irregular heart beat indicating stress, 4/5 IND regained consciousness, spectral analyses questioned whether unconsciousness was actually achieved, and c) spiking required expertise to execute effectively, otherwise in >60% of IND unconsciousness was not induced 120.

SPAWNERS:

WILD: does not apply.
FARM: no data found yet.
LAB: no data found yet.

Side note: Domestication

Teletchea and Fontaine introduced 5 domestication levels illustrating how far species are from having their life cycle closed in captivity without wild input, how long they have been reared in captivity, and whether breeding programmes are in place.

What is the species’ domestication level?

DOMESTICATION LEVEL 5 121, fully domesticated.

Side note: Forage fish in the feed

450-1,000 milliard wild-caught fishes end up being processed into fish meal and fish oil each year which contributes to overfishing and represents enormous suffering. There is a broad range of feeding types within species reared in captivity.

To what degree may fish meal and fish oil based on forage fish be replaced by non-forage fishery components (e.g., poultry blood meal) or sustainable sources (e.g., soybean cake)?

All age classes:

WILD: opportunistic – either mainly herbivorous 6 (non-native habitat: 45 44 49 122 88) or mainly omnivorous (non-native habitat: 8 48 43 50).
FARM: fish meal may be completely* replaced by non-forage fishery components 123. Ponds: no external feed administered in extensive culture systems 11. Cages: feed without fish meal and fish oil 26. Higher growth of SPAWNERS in fertilised than unfertilised ponds, higher number of hatched FRY at 25-30% protein level for SPAWNERS in pre-spawning period 14.
LAB: fish meal may be completely* replaced be some sustainable sources 124, not 125 126, partly* 127, or mostly* replaced by other sustainable sources 128. Fish meal may be partly* replaced by non-forage fishery components 129 130. Fish oil may be completely* replaced by some sustainable sources 131 132, partly* by other sustainable sources 133.

^{*partly = <51% – mostly = 51-99% – completely = 100%}

Glossary

ADULTS = mature individuals
DOMESTICATION LEVEL 5 = selective breeding programmes are used focusing on specific goals 121
EURYHALINE = tolerant of a wide range of salinities
FARM = setting in farming environment or under conditions simulating farming environment in terms of size of facility or number of individuals
FINGERLINGS = early juveniles with fully developed scales and working fins, the size of a human finger
FRY = larvae from external feeding on
IND = individuals
JUVENILES = fully developed but immature individuals
LAB = setting in laboratory environment
LARVAE = hatching to mouth opening
NTU = Nephelometric Turbidity Units
PHOTOPERIOD = duration of daylight
POTAMODROMOUS = migrating within fresh water
RAS = Recirculating Aquaculture System - almost completely closed system using filters to clean and recirculate water with the aim of reducing water input and with the advantage of enabling close control of environmental parameters to maintain high water quality
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
TOTAL LENGTH = from snout to tip of caudal fin as compared to fork length (which measures from snout to fork of caudal fin) or standard length (from head to base of tail fin) or body length (from the base of the eye notch to the posterior end of the telson) 41
WILD = setting in the wild

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