African sharptooth catfish

Clarias gariepinus

Clarias gariepinus (African sharptooth catfish)
Taxonomy
    • Osteichthyes
      • Siluriformes
        • Clariidae
          • Clarias gariepinus
Distribution
Distribution map: Clarias gariepinus (African sharptooth catfish)

Information


Author: Jenny Volstorf
Version: 2.0 (2019-12-14)

Cite

Reviewers: N/A
Editor: Billo Heinzpeter Studer

Cite as: »Volstorf, Jenny. 2019. Clarias gariepinus (Farm: Recommendations). In: FishEthoBase, ed. Fish Ethology and Welfare Group. World Wide Web electronic publication. First published 2019-05-09. Version 2.0. https://fishethobase.net.«





1  Overview

No data found yet.


2  General

  • Escapes: rear only in environments where it naturally occurs F1 and prevent escapes. Else, escapees from fish farms have negative or at most unpredictable influences on the local ecosystem F2. Prepare for sexual maturity (and thus spawning) from 0-6 years or 17-92 cm on for males and 0-6 years or 15-74+ cm on for females F3 and take measures against spawning into the wild.



3  Designing the (artificial) habitat

3.1 Substrate and/or shelter

  • Substrate:
    • Substrate: no clear substrate preference F4. For the most natural solution, provide mud, shale, sand, and vegetation. For highest hatching rates, provide eggs with Pistia stratiotes or alternatively Commelina sp. or Eichhornia crassipes. Artificial alternatives were not advantageous compared to barren tanks F5. For better growth in juveniles, install bamboo poles in ponds which probably enable periphyton growth which serves as additional food F5.
    • For substrate and...
      ...spawning R1,
      ...occupation  R2.
  • Shelter or cover:
    • Cover: in the wild, takes cover from overhead under vegetation and occasionally mud banks F6. For the most natural solution, provide vegetation or mud banks; alternatively, provide artificial shelters inside the system or outside (e.g., black plastic shade material F7, black nylon shadecloth netting F8, aluminium roof plates F9). Although 0 hours photoperiod or full cover respectively F8 F10 increased growth in fry, refrain from complete cover in respect for differences in the daily rhythms R3 and because we have not found studies reporting possible long-term effects on welfare FishEthoBase's understanding of fish welfare.
    • Vegetation: Cover.
    • Shelters: in the wild, occasionally seeks shelter under rocks F6. For the most natural solution, provide rocks; alternatively, provide artificial shelters inside the system or outside. Enrichment with shelters probably increases the value for fry, but this may cause attacks and chases to establish territories F7. Further research needed to determine whether this holds also in farm environments.
    • Safety measures: provide access to the water surface so that individuals may breathe; ensure safety measures to avoid individuals jumping out of the holding system F11.


3.2 Photoperiod

  • Photoperiod: given the distribution F1 F12, natural photoperiod is 9-15 hours, depending on the season. Provide access to natural (or at least simulated) photoperiod and daylight. Some evidence to best keep larvae in dark surrounding F13. Further research needed. Also for juveniles, 24 hours photoperiod is stressful; stress decreases F14 and growth increases with decreasing photoperiod F15 F16. Further research needed.
  • Light intensity: for larvae (0-3 days), provide low light intensity to accommodate the photonegative behaviour F13. To accommodate preference in fry F16 and for lower stress in juveniles, provide ≤15 lux F17. Further research needed.
  • Light colour: for lower aggression under light intensities of 0.002-1.4 µmoles/m2/s, provide blue light F18. Further research needed.
  • Resting period: allow African catfish a resting period at night or in the dark F13.


3.3 Water parameters

  • Temperature: no clear temperature preference, probably best kept at 16-25 °C F19, eggs at 26-30 °C F20. Below may mean lower survival, but it depends on age and rate of temperature change F21. Adjust temperature when you notice avoidance behaviour F6 F22. Avoid exposing 5 day-old fry to sudden, gradual, or fluctuating temperature changes of 10 °C or more, as it increases mortality F21. Fry from 21 days on are more adaptive, but do not tolerate temperatures of 10 °C or below F21.
    Implemented in aquaculture, temperatures >22 °C demand excellent oxygen levels F23 and a fine-tuned flow-through system to prevent bacterial load.
    For temperature and spawning  R1.
  • Water velocity: no clear velocity preference F24. Provide variations in the direction and the velocity of the water inlet, depending on life stage F24. Further research needed.
  • Oxygen: in the wild, oxygen level is at 61-82% or 5.1-6.9 mg/L. Maintain oxygen level that ensures welfare depending on temperature ( Temperature) and stocking density ( R4).
  • Salinity: given the potamodromous migration type, natural salinity is at freshwater level from egg to adult stage F25 F26.
  • pH: in the wild, pH is at 7.0-9.2 F27. For the most natural solution, maintain this range. Further research needed.
  • Turbidity: in the wild, turbidity is at 18.9-257 ntu, 533.3-1,256 ppm total dissolved solids, water transparency is at 0.05-3.5 m Secchi depth F28. For the most natural solution, maintain turbidity at this range. Further research needed.


3.4 Swimming space (distance, depth)

  • Distance: in the wild, remains in home range of ≤40 m or in area of 1,600-2,000 m2 for months, but individuals differ in number of long-term movements in areas of up to 70,000 m2 F29. Further research needed. Provide at least 40+ m, bearing in mind the planned stocking density R4.
  • Depth:
    • Depth range: in the wild, found at 0.1-10 m, adults up to 40 m F30 F31. Provide at least 2-4 m, ideally up to 10 m or more, bearing in mind the planned stocking density R4. Individuals should be able to choose swimming depths according to life stage, time of day, and status F30 F11.
    • Flight: no ethology-based recommendation definable so far.
    • Temperature layers: in habitats with water layers with different temperatures, prepare for individuals migrating to layers with preferred temperatures F19, and avoid crowding in these layers by providing enough space.



4  Feeding

  • Alternative species: mainly carnivorous F32, trophic level 3.8 F33. If you have not yet established an African catfish farm, you might consider to opt for a species that can be fed without or with much less fish meal and fish oil in order not to contribute to overfishing by your business F34.
  • Protein substitution: if you run an African catfish farm already, try to substitute protein feed components that have so far been derived from wild fish catch, while taking care to provide your fishes with a species-appropriate feed F32:
    • Invite a feed mill and other fish farmers in your country to jointly establish a recycling syndicate that converts the remainders and the offcuts of fish processing into fish meal and fish oil, separating the production line corresponding to the species of origin in order to avoid cannibalism  fair-fish farm directives (point 6).
    • Inform yourself about commercially tested substitutes for fish meal and fish oil, like insect or worm meal or soy, with an appropriate amino and fatty acid spectrum.
  • Feed delivery:
    • Feeding frequency and time, feed delivery, self-feeders: in the wild, ram feeder or wounds prey F35; feeds on insect larvae rather during the day, fish prey rather during the night F35 F13. Seems to adjust to feeding exclusively during daytime F13. For less aggression and higher growth, choose a lower rather than higher feeding frequency (2-3 times/day) and make sure to provide in excess feed to avoid food competition, as feed supply seems to be the most important factor (over shelter and density) to prevent cannibalism F36 F37 F38; alternatively, for higher growth and lower food wastage, install a belt feeder and provide the majority of feed during the night F37; alternatively, to decrease swimming and increase resting activity, install a self-feeder and make sure all African catfish adapt to it F36. Further research needed. In case of feeding per hand, for a more homogeneous size distribution, provide feed spatially dispersed rather than localised F39. Note decreased feeding in winter F22 and in risky or new situations given personality differences F40 F41 and reduce the amount of food offered accordingly (if not using a self-feeder). Further research needed. To increase feed consumption, use amino acids (methionine, alanine, glutamine, cysteine) F42. Refrain from ablation of barbels, as this decreases feed consumption F43, is a profound invasion into the integrity and dignity of the individual, and because we have not found studies reporting possible long-term effects on welfare  FishEthoBase's understanding of fish welfare.
    • Food competition: make sure to provide sufficient feed from ca 2-4 days after hatching on F44. Although food competition increases cannibalism F38 and because dominant individuals might monopolise feed F45, refrain from size-grading, as it might not increase growth F46, does not decrease aggression F47, and affects swimming, resting, and feeding behaviour F48. Further research needed.
  • Particle size: in the wild, chooses prey 1/4-1/8 the size of the own body; in the laboratory, if given prey of different sizes, fry and juveniles preferred larger rather than smaller prey (1/22-1/2 of body size or 1/2 of mouth width) F32. For fry and juveniles, provide particle sizes of 1/22-1/2, but make sure that individuals accept it, as transition to a different diet might be a reason for cannibalism F49.
  • Feed enrichment: no ethology-based recommendation definable so far.



5  Growth

  • Maturity: in the wild, matures at 0-6 years F3. Even if manipulating time of maturity were possible, refrain from it, as we have not found studies reporting possible long-term effects on welfare FishEthoBase's understanding of fish welfare.
  • Manipulating sex: even if manipulating sex were possible, refrain from it, as we have not found studies reporting possible long-term effects on welfare FishEthoBase's understanding of fish welfare.
  • Sex ratio: in the wild, sex ratio of males to females varies between equality, majority of females (up to 1:1.5) to majority of males (1.2:1-3.8:1) F50. Maintain a sex ratio that ensures welfare. Although males develop faster and grow bigger than females F51, refrain from monosex (male-only) groups, as the sex difference is not large enough that it cannot be overturned by domestication F52 and as we have not found studies reporting possible long-term effects on welfare  FishEthoBase's understanding of fish welfare.
  • Size-grading: when in small groups, better size-grade fry, fingerlings, and juveniles, otherwise they aggressively establish a social hierarchy F53. In larger groups, comparable growth F46 and aggression in single-size and mixed-size populations F47. Among similar-sized individuals, possible decrease in aggression but only in medium- and heavy-weight groups and instead effects on feeding, siwmming, and resting behaviour and no decrease in stress F48, so size-grading does not seem beneficial.
  • Other effects on growth:
    • Tank colour: for higher survival F54 and better growth in fry, provide black tanks F10. Further research needed.
    • Tank design: for better growth in fry, provide shallower than deeper tanks (14.5 diameter-to-depth ratio or 0.1 m2 x 0.03 m depth) F55. Further research needed.
    • Polyculture: in the wild, co-exists with Banded tilapia, Bluefin dwarf, Burrowing goby, Eastern bottlenose elephant snout, Estuarine round herring, Leaden labeo, Natal topminnow, Redbreast tilapia, Sibayi goby, Southern mouth-brooder, Striped topminnow, Tank goby, Wahrindi F56. Possible benefit of polyculture (at least for Nile tilapia at density of 30,000 individuals/ha), but depends on the second species and stocking density F55. Further research needed.
  • Deformities and malformations: prone to head abnormalities and – to a lesser degree – deformities of spine and fins, tumours or skin erosions decreasing growth and survival F57. For fewer deformities, avoid using cryopreserved sperm, as this causes haploidy which might result in deformities F58 and avoid stressful handling (resulting in bruises), air exposure, transport with low oxygen supply, starvation, chasing, and increase in stocking density in spawning females F59. Further research needed.
  • For growth and...
    ...substrate and shelter  R5,
    ...photoperiod  R3,
    ...water temperature  R6,
    ...feeding frequency  R7,
    ...stocking density  R4.



6  Reproduction

  • Nest building: no nest building F60, lake spawner at shore or in inundated grassland with submerged terrestrial vegetation F61 F62 F63. Females disperse eggs via tail fin to enhance survival which is decreased on sand or in detritus F63. For the most natural solution, provide submerged terrestrial vegetation.
  • Courtship, mating: respect courtship behaviour in which the male butts the female softly on abdomen, head, and tail, both quiver and butt each other for 1-2 hours F61. Allow for unlimited contact between partners due to importance of olfaction and (even if minor) importance of vision and hearing for ovarian growth F42.
  • Spawning conditions: for spawning substrate Nest building (above). Respect natural spawning season in summer at >22 °C at night in fresh water in shallow depth up to 40 cm pools and density of up to 30-60 individuals/125 m shoreline F62. Further research needed. Successful spawning and long spawning duration has been achieved at 25 cm depth at density of one pair per tank F64. No ethology-based recommendation definable on water velocity and broodstock composition. Respect the natural spawning sequence in which male and female remain in a quasi amplexus, relase eggs and sperm in water, and repeat the sequence several times for up to 1-2 hours F65. Further research needed.
  • Fecundity: in the wild, 2,000-650,000 eggs per female or 339,000-1,176,000 eggs per kg body weight F66. For higher fecundity, fertilisation rate, hatching rate, and survival and deformity rate of larvae, avoid rough handling resulting in bruises, air exposure, transport, starvation, increasing density before spawning F59. Although manipulating fecundity is possible F67, refrain from it, 1) as hormones do not seem to be the only factor influencing fecundity and might not work F67, 2) despite increased sperm count handstripping remains difficult F67, and 3) as we have not found studies reporting possible long-term effects on welfare FishEthoBase's understanding of fish welfare.



7  Stocking density

  • Maximum: the businessplan should be calculated on the basis of a maximum stocking density that will never exceed the tolerable maximum with regard to fish welfare.
  • Stocking:
    • Stocking larvae: no ethology-based recommendation definable so far.
    • Stocking juveniles and adults: in the wild, low density (1.3-14.4 catch per unit effort, 0-20 individuals/125 m shore line) F31. Further research needed. Mixed results on effects of density in captivity that might be due to high adaptability to high densities, but to be on the safe side, for better welfare and growth, keep at <50 individuals/L, preferably even <10-22 individuals/L F9 F68.
  • Restriction:
    • Habitat structuring: consider loss of space due to structures inside and outside the system R5 and calculate density accordingly.
    • Environmental conditions: in the wild, displays a large variability in preferences for substrate F4 and depth F30. Consider increased density at places with preferential conditions R5 R8 and calculate density accordingly.
    • Aggregation: in the wild, individuals form aggregations F69 or feed in shoals F35. Consider increased density at places due to formation of aggregations or shoals and calculate density accordingly.
    • Aggression: choose density given displayed aggression between a) tendency of higher number of aggressive acts (including cannibalism) at low density and b) higher frequency of swimming – and thus more opportunity of contacts – as well as tendency of higher mortality at higher density and adjust accordingly F9 F70. Further research needed. Aggression may entail attacks, chases, bites F47.
    • Territoriality: in captivity, territorial F71. Consider space loss due to territoriality and calculate density accordingly.
  • Interaction: as show the above influence factors, stocking density is only one part of a complex interaction of factors to affect welfare. It should never be considered isolatedly.



8  Occupation

  • Food search: provide submerged vegetation, mud, shale, or sand so that individuals may search for food F4 F35.
  • Challenges: if after decreasing stress R9 and providing everything welfare assuring, you still notice stereotypical behaviour or vacuum activities F72 or sadness, then provide mental challenges (e.g., colour vision games F73), diversion, variety, and check reactions.



9  Handling, slaughter

9.1 Handling

  • Stress coping styles: individuals differ in their ability to cope with stress F40 F41, so assume the smallest common denominator during stressful situations and handle with care and high efficiency.
  • Stress measurement:
  • Stress reduction:
    • Noise: no ethology-based recommendation definable so far.
    • Directing individuals: to direct individuals in the habitat (e.g., for cleaning purposes), make use of African catfish's ability to be conditionable F79 to reduce stress.
    • Cage submergence: no ethology-based recommendation definable so far.
    • Pain treatment: no ethology-based recommendation definable so far.
    • Handling: handle as carefully as possible, as it causes stress F74 and might result in defense via erecting pectoral stings that can cause serious injuries F81. If only a sample of individuals is to be handled, separate them from the main population to not stress the uninvolved conspecifics F82 F83.
      For handling spawning females  R1.
    • Confinement: no ethology-based recommendation definable so far.
    • Crowding: no ethology-based recommendation definable so far.
    • Transport: avoid live transport, as it causes stress F75. If unavoidable, after transport for three hours, let recuperate for at least 24-48 hours F75.
    • Disturbance: no ethology-based recommendation definable so far.
    • For stress reduction and...
      ...cover  R5,
      ...photoperiod, light intensity, light colour  R3,
      ...water temperature  R6,
      ...feeding frequency, food competition R7,
      ...tank colour, deformities  R10,
      ...stocking density  R4,
      ...stunning  R11.


9.2 Slaughter

  • Stunning rules: render individuals unconscious as fast as possible and make sure stunning worked and they cannot recover F84.
  • Stunning methods: prefer electrical stunning for one second at 350 V (50 Hertz AC) and in combination with either captive needle pistol or decapitation if only the head is stunned F85. Alternatively, use shooting with captive needle pistol and placement in ice water afterwards, because it renders individuals unconscious fast if administered correctly and with sufficient force F85. Refrain from stunning via live chilling, as latency to loss of movement, as well as cramps, and tachycardia indicate stress F85.
  • Slaughter methods: bleed or gut individuals immediately after stunning, i.e. while unconscious.



10  Certification

  • Certification: fair-fish international association warmly advises to follow one of the established certification schemes in aquaculture in order to improve the sustainability of aquafarming. Adhering to the principles of one of these schemes, however, does not result in animal welfare by itself, because all these schemes do not treat animal welfare as a core issue or as an issue at all. Therefore the FishEthoBase has been designed as a complement to any of the established certification schemes. May it help practitioners to improve the living of the animals they farm based on best scientific evidence at hand.
  • To give you a short overview of the most established schemes, we present them below in descending order of their attention for animal welfare (which is not necessarily the order of their sustainability performance):
    • The fair-fish farm directives are not present on the market, we cite them here as a benchmark. The directives address fish welfare directly by being committed to FishEthoBase: for each species, specific guidelines are to be developed mirroring the recommendations of FishEthoBase; species not yet described by FishEthoBase cannot be certified. In addition, the directives address a solution path for the problem of species-appropriate feeding without contributing to overfishing.
    • The Naturland Standards for Organic Aquaculture (Version 06/2018) generally address animal welfare with words similar to the fair-fish approach: "The husbandry conditions must take the specific needs of each species into account as far as possible (…) and enable the animal to behave in a way natural to the species; this refers, in particular, to behavioural needs regarding movement, resting and feeding as well as social and reproduction habits. The husbandry systems shall be designed in this respect, e.g. with regard to stocking density, soil, shelter, shade and flow conditions."
      In the details, however, the standards scarcely indicate tangible directives for African catfish, except for tropical freshwater species in general when kept in ponds or net cages: no grow-out in artificial tanks, stocking density limited to 10 kg fish/m3 max.
    • The GAA-BAP Finfish and Crustacean Farms Standard (Issue 2.4, May 2017) directly addresses animal welfare: "Producers shall demonstrate that all operations on farms are designed and operated with animal welfare in mind." Farms shall "provide well-designed facilities", "minimize stressful situations" and train staff "to provide appropriate levels of husbandry". Yet the standard does not provide tangible and detailed instructions for the practitioner, let alone species-specific directives.
      In September 2017, GAA-BAP received a grant from the Open Philanthropy Project to develop best practices and proposed animal welfare standards for salmonids, tilapia, and channel catfish. Thus, fish welfare on GAA-BAP certified farms might become more tangible in the future, eventually also for African catfish at a later date.
    • The GlobalG.A.P. Aquaculture Standard (Version 4.0, March 2013) "sets criteria for legal compliance, for food safety, worker occupational health and safety, animal welfare, and environmental and ecological care". The inspection form includes criteria like "Is the farm management able to explain how they fulfil their legal obligations with respect to animal welfare?", "If brood fish are stripped, this should be done with the consideration of the animal's welfare." or "Is a risk assessment for animal welfare undertaken?". The scheme claims that 45 out of a total of 249 control points cover animal protection, yet it does not provide any tangible directives, let alone species-specific directives.
    • The ASC Aquaculture Stewardship CouncilThe ASC standards address fish welfare only indirectly, as a function of a "minimum average growth rate" per day, a "maximum fish density at any time", and a "maximum average real percentage mortality". fair-fish sees animal welfare as an intrinsic value, not just as a result of optimising neighbouring values like health care and management procedures. 
      There is no ASC standard for African catfish so far.
      In November 2017, ASC received a grant from the Open Philanthropy Project to develop an evidence-based fish welfare standard that is applicable to all ASC-certified species. ASC intends to share its approach to fish welfare with all farms engaged with the ASC program and encourage adoption of it, which means that the fish welfare standard will function as a non-mandatory add-on to the ASC certification.
    • The Friend of the Sea (FOS) Standards for freshwater aquaculture of fish (revised October 2016) do not even address animal health or animal welfare issues.
      In May 2017 however, FOS signed a Memory of Understanding with fair-fish international on developing fish welfare criteria for the FOS standard. In November 2017 fair-fish international association received a grant from the Open Philanthropy Project to assess the welfare of fish on FOS certified farms, develop farm-specific recommendations, and to develop animal welfare criteria for the FOS standard. Thus, fish welfare on FOS certified farms might become tangible in the future.







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