Short profile


FishEthoScore of the species

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

Criteria Li Po Ce
1 Home range ?
2 Depth range
3 Migration
4 Reproduction
5 Aggregation ?
6 Aggression
7 Substrate
8 Stress
9 Malformation
10 Slaughter
FishEthoScore 3 8 6
Li = Likelihood that the individuals of the species experience welfare under minimal farming conditions
Po = Potential overall potential of the individuals of the species to experience welfare under improved farming conditions
Ce = Certainty of our findings in Likelihood and Potential
 
                    ?     /  
  High    Medium     Low     Unclear  No findings
 
FishEthoScore = Sum of criteria scoring "High" (max. 10)



General remarks

Oreochromis niloticus is a very resilient and well-known species to the aquaculture industry. However, it requires a series of features to ensure its welfare in farming conditions. Intensive farming may disrupt natural reproductive cycles and fails to ensure that proper substrate and shelter are provided. Semi-intensive culture respect some spatial and habitat needs, but most industrial farming, especially in floating cages, does not. Although a remarkable amount of research has been conducted, another issue that needs to be tackled is wild-caught fish for feed. This should be replaced by fish slaughterhouse waste and other sources or avoided by extensive farming fully based on sustainable sources.


1. Are minimal farming conditions likely to provide the home range of the species? Is there potential for improvement? How certain are these findings?

?
Likelihood
H
Potential
M
Certainty

LARVAE: WILD: maternally mouthbred [1] [2] [3] [4] [5], young remain close to the mother [6]. FARM: <4 m[7].

JUVENILES: WILD: move considerably between feeding and breeding grounds [6]. FARM: grow-out ponds: 690 [8], 2000 m[7]; hapas: 120 m2 [7]; cages 6-600 m3 [8].

ADULTS  JUVENILES:

SPAWNERS: WILD: males: 2-10 m [9]; mouthbreeding females move away from spawning grounds, unknown distance [6]. FARM: spawning ponds: < 2000 m[7]; hapas: 120 m[7]; raceways: 12 m[8].


2. Are minimal farming conditions likely to provide the depth range of the species? Is there potential for improvement? How certain are these findings?

L
Likelihood
H
Potential
H
Certainty

Eggs: WILD: maternally mouthbred [1] [2] [3] [4] [5]FARM: incubation jars [7].

LARVAE: WILD: maternally mouthbred [1] [2] [3] [4] [5], usually in shallow habitats [10] [6]. FARM: nursery concrete tanks: 0.5-2 m [8]; earthen ponds: ca 1 m [8]; intensive artificial larval rearing systems: ca 20 cm [8].

JUVENILES: WILD: usually 0-6.7 m [11] [3], occasionally below 30 m [12]. Move deeper with decreasing water temperatures and shallower with increasing water temperatures [13]. FARM: grow-out concrete tanks: 1-2 m [13] [8]; ponds: 0.5-3 m [13] [8]; cages: 2-4 m [8].

ADULTS:  JUVENILES

SPAWNERSWILD: build nests in shallow waters [12], usually at 0.6-2 m [14]. FARM: spawning concrete tanks: 0.5-2 m; earthen ponds: ca 1 m [8].


3. Are minimal farming conditions compatible with the migrating or habitat-changing behaviour of the species? Is there potential for improvement? How certain are these findings?

H
Likelihood
H
Potential
H
Certainty

Typically resident in fresh water [15] [6]. Able to adapt to brackish water [2].

LARVAEWILD: maternally mouthbred in fresh or brackish water [1] [2] [3] [4] [5]FARM: nursery freshwater ponds [7]. For details of holding systems  crit 1 and 2.

JUVENILES: WILD: fresh water, perform temperature-related depth displacements [13]FARM: reared in fresh water [8] [7]. For details of holding systems  crit 1 and 2.

ADULTS JUVENILES.

SPAWNERS:  fresh water [9] [6].  FARM:  JUVENILES.


4. Is the species likely to reproduce in captivity without manipulation? Is there potential to allow for it under farming conditions? How certain are these findings?

H
Likelihood
H
Potential
H
Certainty

WILD: breed in a lek system: many males gather in an arena to display to females around it. Each male digs and defends a pit in sandy substrate where he performs elaborate behaviours, changes colour and sometimes chases females into the pit. One female then lays the eggs in the pit, the male fertilizes the clutch and the female grabs the fertilized eggs with her mouth, swimming away [6] [16] [17] [18]. FARM: spawns easily and spontaneously in hapas, earthen ponds and concrete tanks [8] (although these lack substrate) but not in floating cages - which therefore are not used for spawning [7].


5. Is the aggregation imposed by minimal farming conditions likely to be compatible with the natural behaviour of the species? Is there potential to allow for it under farming conditions? How certain are these findings?

?
Likelihood
H
Potential
M
Certainty

LARVAEWILD: maternally mouthbred [1] [2] [3] [4] [5], spend early life stages in same-age group of siblings [5]. Fry form large schools [19]. FARM: extensive and semi-intensive systems: eggs hatch and larvae develop with mothers in spawning tanks or ponds [8]; artificial hatching systems in intensive rearing: 2-10 fry/L [20].

JUVENILES: WILD: live in groups of unknown, variable sizes in the wild [6] [10] [5]. FARM: form groups in captivity [21] [22]. Semi-intensive ponds: 1-3 juveniles/m2; raceways and floating cages: 200-300 juveniles/m3 [7].

ADULTS:  JUVENILES.

SPAWNERS: WILD: gather in leks (i.e. spawning arenas) [6] [8]. FARM: 2-28 adults/m2 in 1 male : 3 females sex ratio [8].


6. Is the species likely to be non-aggressive and non-territorial? Is there potential for improvement? How certain are these findings?

L
Likelihood
M
Potential
M
Certainty

LARVAE: WILD: maternally mouthbred [1] [2] [3] [4] [5], spend early life stages in same-age group of siblings [5]. FARM: fry form large schools [19]. No reports of aggression.

JUVENILES: WILD: territorial, aggressive in the wild [15] [23] [24] [25] [26] [27]FARM: aggression decreases severely when density increases [28] [29].

ADULTS:  JUVENILES.

SPAWNERSWILD and FARM: territorial, aggressive within the spawning season [15] [23] [24] [25] [27].


7. Are minimal farming conditions likely to match the natural substrate and shelter needs of the species? Is there potential for improvement? How certain are these findings?

L
Likelihood
H
Potential
H
Certainty

Eggs and LARVAE: WILD: maternally mouthbred [1] [2] [3] [4] [5], usually in shallow sandy vegetated habitats [10]. FARM: substrate present in earthen ponds [8] [30].

JUVENILES: WILD: benthic, use substrate for feeding [31] [11] [32] [33]. FARM: grow better with substrate [30], which is present in earthen ponds [8] [30].

ADULTS:  JUVENILES.

SPAWNERSWILD: benthic, use substrate for feeding [31] [11] [32] [33] and spawning [17] [18] [6] [20] [10] [5] [34]. FARM: substrate present in earthen ponds [8] [30], but are able to spawn without substrate [8].


8. Are minimal farming conditions (handling, confinement etc.) likely not to stress the individuals of the species? Is there potential for improvement? How certain are these findings?

L
Likelihood
M
Potential
M
Certainty

Eggs: no data found yet.

LARVAEno data found yet.

JUVENILES: Display acute stress reponse to handling [35] and to environmental and social stressors [36] [37] [38] [39]

ADULTS JUVENILES.

SPAWNERS JUVENILES.


9. Are malformations of this species likely to be rare under farming conditions? Is there potential for improvement? How certain are these findings?

H
Likelihood
H
Potential
H
Certainty

LARVAE: no influence of intense inbreeding on fry malformation rates:  3-8% [40].

JUVENILES: low rate (1.5-2.7%) of skeletal deformities (lateral projections of the mandible, 'parrot-like head', scoliosis, kyphosis, lordosis, fusion of dorsal and anal fins) [41] when compared to other farmed species such as sea bass (30%) [42], sea bream (>10%) [43] or catfish (5%) [41].

ADULTS JUVENILES.


10. Is a humane slaughter protocol likely to be applied under minimal farming conditions? Is there potential for improvement? How certain are these findings?

L
Likelihood
H
Potential
H
Certainty

Electrical stunning methods and effects are studied [44] [45] [46] and applied in some farms [47]. Most effective stunning after 5s (50Hz ac, 1 A/dm2) and chilling for 15 min in ice slurry [44] [46]. Industrial apparatus is available for commercial use [48].


Side note: Domestication

DOMESTICATION LEVEL 5 [49], fully domesticated.


Side note: Feeding without components of forage fishery

WILD: Omnivorous [11] [12] [31] [50]. FARM: fish feed and fish oil may be mostly* [51] or completely* replaced by non-forage fishery products [52] [53] [54] , especially in integrated farming [8] or non-industrial practices (urban aquaponic) [55].

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


Glossary

ADULTS = mature individuals, for details Findings 10.1 Ontogenetic development
DOMESTICATION LEVEL 5 = selective breeding programmes are used focusing on specific goals [49]
FARM = setting in farm environment
JUVENILES = fully developed but immature individuals, for details Findings 10.1 Ontogenetic development
LARVAE = hatching to mouth opening, for details Findings 10.1 Ontogenetic development
SPAWNERS = adults that are kept as broodstock
WILD = setting in the wild


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