European seabass

Dicentrachus labrax

Dicentrachus labrax (European seabass)
Taxonomy
    • Osteichthyes
      • Perciformes
        • Moronidae
          • Dicentrachus labrax
Distribution
Distribution map: Dicentrachus labrax (European seabass)

Information


Author: Jenny Volstorf
Version: 2.0 (2019-12-13)

Cite

Reviewer: Kerstin Glaus
Editor: Billo Heinzpeter Studer

Cite as: »Volstorf, Jenny. 2019. Dicentrachus labrax (Farm: Recommendations). In: FishEthoBase, ed. Fish Ethology and Welfare Group. World Wide Web electronic publication. First published 2016-03-15. 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 7 years or 33-34 cm on for males and 5 years or 38-42 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 sand as well as mud and different kinds of vegetation.
    • For substrate and occupation  R1.
  • Shelter or cover:
    • Cover: avoid complete cover in respect for the diurnal rhythm R2.
    • Vegetation: Substrate.
    • Shelters: no ethology-based recommendation definable so far.
    • Safety measures: ensure safety measures to avoid individuals jumping out of the holding system F5.


3.2 Photoperiod

  • Photoperiod: given the distribution F1, natural photoperiod is 8-18 hours, depending on the season. Provide access to natural (or at least simulated) photoperiod and daylight.
  • Light intensity: no ethology-based recommendation definable so far.
  • Light colour: no ethology-based recommendation definable so far.
  • Resting period: respect the diurnal rhythm of European seabass and its resting period at night or in the dark F6.


3.3 Water parameters

  • Temperature: no clear temperature preference, probably best kept at 18-26 °C F7. Below may mean lower survial F8 and growth F9. Adjust temperature when you notice avoidance behaviour F10. Avoid daily temperature changes between 17 and 23 °C in juveniles from hatching to 6 months, as this is a larger stressor than scrubbing for five minutes three times a day F8.
    Implemented in aquaculture, temperatures >22 °C demand excellent oxygen levels F11 and a fine-tuned flow-through system to prevent bacterial load. If temperatures <18 °C cannot be avoided, decrease water velocity F10.
    For temperature and spawning  R3.
  • Water velocity: no clear velocity preference F12. Provide variations in the direction and the velocity of the water inlet preferably between 0 and 200+ cm/min F12.
  • Oxygen: in the wild, oxygen level is at 4.5-12 mg/L F11. Further research needed. Maintain oxygen level that ensures welfare depending on temperature ( Temperature) and stocking density ( R4).
  • Salinity: given the amphidromous migration type, natural salinity is at fresh or brackish water level from post-larvae to juvenile stage and seawater level at juvenile and adult stage F13 F14.
  • pH: no ethology-based recommendation definable so far.
  • Turbidity: no ethology-based recommendation definable so far.


3.4 Swimming space (distance, depth)

  • Distance: in the wild, majority of juveniles and adults remain at a radius of 16 km around tagging site F15. Provide enough space, bearing in mind the planned stocking density R4.
  • Depth:
    • Depth range: in the wild, found at 0.8-73 m F16. Provide at least 3-5 m, ideally up to 73 m, bearing in mind the planned stocking density R4.
    • 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 F7, and avoid crowding in these layers by providing enough space.



4  Feeding

  • Alternative species: carnivorous F17, trophic level 3-4.6 F18. If you have not yet established a European seabass 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 F19.
  • Protein substitution: if you run a European seabass salmon 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 F17:
    • 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, bottom grazer or active pursuer F20 F21, mostly diurnal F6. Refrain from feeding during night time in respect for European seabass' natural resting period. No ethology-based recommendation definable so far on frequency as well as speed and pattern of feed delivery. For better growth, feed to satiation, not just maintenance F22. Note decreased feeding in new situations given personality differences F23 and reduce the amount of food offered accordingly. Alternatively, install a self-feeder and make sure all European seabass adapt to it.
    • Food competition: make sure to provide sufficient feed from ca 9 days after hatching on F24. In habitats with self-feeders, there is no food competition but social organisation of producers and scroungers where few individuals trigger a majority of feed without difference in growth F25.
  • Particle size: no ethology-based recommendation definable so far.
  • Feed enrichment: no ethology-based recommendation definable so far.



5  Growth

  • Maturity: in the wild, matures at 5-7 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: although manipulating sex is possible F26, 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 of 1:2 F27. Further research needed. For the most natural solution, maintain this sex ratio. Although females develop faster and grow bigger and heavier than males F28, refrain from monosex (female-only) groups, as we have not found studies reporting possible long-term effects on welfare  FishEthoBase's understanding of fish welfare.
  • Size-grading: in captivity, no effect of size-grading on growth F29 and aggression F30, because European seabass hardly displays aggression. So, size-grading does not seem beneficial.
  • Other effects on growth:
    • Polyculture: in the wild, co-exists with Grey mullet, Sole F31. Further research needed for benefits of polyculture.
  • Deformities and malformations: no ethology-based recommendation definable so far.
  • For growth and...
    ...water temperature  R5,
    ...stocking density  R4.



6  Reproduction

  • Nest building: sea spawner F32.
  • Courtship, mating: no ethology-based recommendation definable so far.
  • Spawning conditions: respect natural spawning season in winter to spring at temperatures of 10-15 °C at 14-35 ppt F33. No ethology-based recommendation definable on water velocity, depth, and spawning sequence. Successful spawning has been achieved in male:female ratios of 1:1 to 1:3 F34. Further research needed for wild ratios.
  • Fecundity: in the wild, 293,000-258,000 eggs per kg body weight F35. Further research needed. Even if manipulating fecundity were possible, refrain from it, 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, juveniles shoal or school at 0.4-1.0 individuals/1,000 m2 in some areas and up to 81.8 individuals/1,000 m2 in other areas F36 F37; adults may shoal or school, too, but may also be solitary F36. Further research needed. For better welfare and growth, keep at <20 kg/m3, preferably even <10 kg/m3 F5.
  • Restriction:
    • Habitat structuring: consider loss of space due to structures inside and outside the system R6 and calculate density accordingly.
    • Environmental conditions: in the wild, displays a large variability in preferences for water temperature F7, water velocity F12, and depth F16. Consider increased density at places with preferential conditions R5 R7 and calculate density accordingly.
    • Aggregation: in the wild, individuals build shoals or schools of up to 560 individuals or 14 m2 area F36. Consider increased density at places due to formation of shoals or schools and calculate density accordingly.
    • Aggression: no ethology-based recommendation definable so far.
    • Territoriality: no ethology-based recommendation definable so far.
  • 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 sand or mud substrate so that individuals may search for food F4 F20.
  • Challenges: if after decreasing stress R8 and providing everything welfare assuring, you still notice stereotypical behaviour, vacuum activities, sadness, then provide mental challenges, diversion, variety, and check reactions.



9  Handling, slaughter

9.1 Handling

  • Stress coping styles: individuals differ in their ability to cope with stress F38 F23, so assume the smallest common denominator during stressful situations and handle with care and high efficiency.
  • Stress measurement:
    • Physiological stress indicators: plasma cortisol exceeding 10-21 ng/mL F39, glucose exceeding 86-114 mg/dL F39 F40 or 5-6 mmol/L F39 indicates stress. As a non-invasive stress indicator, use fin erosion mainly of posterior dorsal and caudal fins and decrease stocking density if you notice erosion  R4.
    • Abnormal behaviour: after, e.g., changing parameters, check for behaviour deviating from the norm F41 F20 F6 F42 F10 F15 F16 F43 F28 F44 F35 F32 F36 F25 F21 F45 F30 F46 F47 F38 F23.
  • 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 European seabass' ability to be conditionable F47 to reduce stress.
    • Cage submergence: consider cage submergence against detrimental surface and weather conditions and because it is less stressful than rearing in surface cages F48.
    • Pain treatment: no ethology-based recommendation definable so far.
    • Handling: no ethology-based recommendation definable so far.
    • Confinement: avoid confinement, as it causes stress F39.
    • Crowding: avoid crowding, as it causes stress F40 F49. If unavoidable, after crowding of 15 minutes, let recuperate for at least 6 hours F40.
    • Transport: no ethology-based recommendation definable so far.
    • Disturbance: no ethology-based recommendation definable so far.
    • For stress reduction and...
      ...water temperature  R5,
      ...feed delivery R9,
      ...stocking density  R4,
      ...stunning  R10.


9.2 Slaughter

  • Stunning rules: render individuals unconscious as fast as possible and make sure stunning worked and they cannot recover F50.
  • Stunning methods: prefer electrical stunning, because it renders individuals unconscious fast if administered correctly and with appropriate current F51. For longer unconsciousness, prefer head-to-tail stunning of restrained individual with 50 Hertz for 10 seconds over one second in seawater F51. Further research needed for a specific protocol. Judging by the muscle pH, immersion in ice/water slurry or chilling on ice would have to be preferred over anaesthesia or percussive stunning, but because of the prolonged struggle time (up to 45 minutes in crowded individuals with ice asphyxia F51), the best alternative is a combination of clove oil and immersion in ice/water slurry, because it combines fast unconsciousness (two minutes) and higher muscle pH F49. EFSA and FDA have not approved the use of clove oil, though.
  • 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 European seabass, except for percids in general when cultured in marine net cages: no grow-out in artificial tanks, stocking density limited to 10 kg fish/m3 max. Live transportation is limited to 10 hours max, to 1 kg/8 L max, and to adequate provision of oxygen, with water exchange after six hours.
    • 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 European seabass 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. 
      The ASC standard for European seabass (version 1.1, March 2019) does not specify threshold values for the above mentioned minima resp. maxima.
      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 marine aquaculture of fish (revised November 2014) 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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