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 0 6 5
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

Clarias gariepinus is a very resilient and fast growing air-breathing fish. It is farmed mostly in Africa, South America, Asia and China, using extensive and traditional methods as well as intensive and industrial techniques. Probably due to its resilience, and despite promising biological traits, some aspects of welfare are either disregarded or overlooked. It is an aggressive fish and easily stressed by usual rearing conditions and practices. It is sensitive to environmental cues when spawning, and usual farming procedures for reproduction are highly invasive. If proper attention is given to these aspects and if reared in conditions that respect spatial needs, it has potential to be reared in good welfare conditions.


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

L
Likelihood
H
Potential
M
Certainty

LARVAE: WILD: remain in shallow vegetated areas [1] [2]. FARM: ponds: 100-150 m2 [3]; tanks: 0.34-2.40 m3 [4].

FINGERLINGS: WILD: may move to deeper areas  [1] [2]FARM: ponds: 100-150 m2 [3]; tanks: 0.34-2.40 m3 [4].

JUVENILES: WILD: diel movements can exceed 200 m, but usually 40-200 m, occasionally <40 m [5]. Yearly home range ca 6 km2 [5]FARM: large variation in pond size: 2-240 m(Africa), 1-2,500 m2 (Bangladesh, Nepal) [6]; tanks: 0.73-10 m3 [4].

ADULTS JUVENILES.

SPAWNERS: WILD: remain in restricted, shallow areas [1] [2]. FARM: large variation in pond size: 2-240 m(Africa), 1-2,500 m2 (Bangladesh, Nepal) [6]; tanks 0.73-10 m3 [4]; natural spawning ponds: 400 m2 [3].


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

LARVAE: WILD: shallow margins of lakes [1]. FARM: 0.4-0.8 m in earthen ponds [3] [7].

JUVENILES: WILD: <1.0-10 m [5]. FARM: ponds: 0.5-3.0 m [6]

ADULTS: WILD and FARM:  Juveniles.

SPAWNERS: WILD: 0.5-2.0 m in spawning season [5] [2]. FARM: 0.5-3.0 m [6]. Natural spawning occurs preferentially at 0.25-0.50 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?

L
Likelihood
H
Potential
H
Certainty

WILD: Freshwater species, resident in lakes [1] [2] [5] [9] [6], streams, rivers, swamps and floodplains [6]. Move from deeper to shallower areas to spawn [2] [5]. FARM: movements can be mimicked by lowering water level [8].

 


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?

L
Likelihood
H
Potential
H
Certainty

WILD: water rising and flooding of margins triggers spawning [2] [6]. Adults move to shallow, recently flooded margins of rivers to spawn during the rainy season (September-March) [9] [6]. Males aggressively compete for access to females, who lay eggs in vegetation [2] [6]. Monogamous spawning [2] [6]. FARM: mostly artificial spawning [3]. Hormonal induction of spawning [10] [11] [3] [6], surgical stripping to collect milt of males, manual stripping of females to collect eggs, manual fertilisation [11] [12] [6]. Triploidy induction is common [11]. However, natural spawning is possible [3] [8].


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
M
Potential
M
Certainty

LARVAE: WILD: no data found yet. FARM: tanks 22,700-29,400 ind/m3 [4].

JUVENILES: WILD: live in abundant groups (Willoughby 1978). FARM: ponds >8 ind/m[7]; tanks: 6,800-9,200 ind/m3 [4].

ADULTS:  JUVENILES

SPAWNERS: WILD: Form large and dense spawning aggregations [2]. FARM: natural spawning in ponds: 0.25-1 ind/m2 [3] [8], hormone-induced spawning inside hapas in ponds: ca 1 ind/m2 [3].


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

L
Likelihood
L
Potential
L
Certainty

LARVAE: WILD: no data found yet.  FARM: cannibalistic, aggressive [13].

JUVENILES: WILD: no data found yet. FARM: aggressive [14] [15].

ADULTS: WILD: no data found yet.

SPAWNERSWILD: aggressive when spawning [2] [6]. FARM: mostly artificial spawning [11] [12] [6]


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

LARVAE: WILD: shallow, vegetated areas, bottom dwellers [1] [2]. Use vegetation for concealment [2]. FARM: Ponds provide natural substrate and vegetation [12] [3]. No reports of substrate enrichment in tanks and cages found in the literature.

FINGERLINGS LARVAE

JUVENILES: WILD: generalist suction feeder [16] [17]. Feed on macrophytes [9]FARM: Ponds provide natural substrate and vegetation [12] [3]. No reports of substrate enrichment in tanks and cages found in the literature.

ADULTS Juveniles.

SPAWNERSWILD: use vegetation in shallow areas to spawn [2] [5] [9]FARM: ponds provide natural substrate and vegetation [12] [3] [8]. No reports of substrate enrichment in tanks and cages found in the literature.


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

LARVAE: sensitive to handling [18].

JUVENILES: stressed by confinement, density [19], long photoperiod [20], handling and transportation [21].

ADULTS:  JUVENILES.

SPAWNERS: females stressed by transportation, handling and emersion [22].


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

L
Likelihood
M
Potential
M
Certainty

LARVAE: 20% broken skull disease due to ascorbic acid deficiency in feed (supplementation solves the issue) [23]; up to 70% intestinal malformation [24] [11], reported to be solved with good rearing conditions and water quality [11].

JUVENILES: no data found yet.

ADULTS: no data found yet.


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

?
Likelihood
H
Potential
H
Certainty

Common and high-standard slaughter method: several protocols available: stunning with captive pistol (8 bar pressure) and chilling in icewater [25], dry electro-stunning (0.76 A, 150 V, AC+DC for 15 s) followed by chilling and decapitation [26] or freshwater electro-stunning (1.60 ± 0.11 A/dm2, 50 Hz, sinusoidal, A.C., conductivity of 876 μS) followed by chilling and decapitation [27].


Side note: Domestication

DOMESTICATION LEVEL 4 [28], level 5 being fully domesticated.


Side note: Feeding without components of forage fishery

All age classes: WILD: mostly carnivorous [1] [2] [9]. FARM: fish meal and fish oil may be completely* replaced by sustainable sources [29] [30] [31].

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


Glossary

ADULTS = mature individuals, for details Findings 10.1 Ontogenetic development
DOMESTICATION LEVEL 4 = entire life cycle closed in captivity without wild inputs [28]
FARM = setting in farm environment
FINGERLINGS = fry with fully developed scales and working fins, the size of a finger; for details Findings 10.1 Ontogentic development
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


Bibliography

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[2] Bruton, M. N. 1979. The breeding biology and early development of Clarias gariepinus (Pisces: Clariidae) in Lake Sibaya, South Africa, with a review of breeding in species of the subgenus Clarias (Clarias). The Transactions of the Zoological Society of London 35: 1–45. https://doi.org/10.1111/j.1096-3642.1979.tb00056.x.
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