Information
Version: B | 1.3 (2024-12-31)
- minor editorial changes plus new side note "Commercial relevance"
WelfareScore | farm
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)
General remarks
Thymallus thymallus is reared for re-stocking and for feeding purposes. It is a highly appreciated species for sports fishing in northern Europe, where several initiatives have been undertaken for conservation of endangered populations. Its breeding in aquaculture relies mostly on wild parents, and many aspects of its rearing remain undisclosed. In addition, several welfare issues are probably not addressed so further research should focus mainly on substrate needs and stress effects of farming, spatial needs, reproduction without manipulation, aggregation, aggression, territoriality, and humane slaughtering.
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 low for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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. It is high for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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 high for minimal and high-standard farming conditions. Our conclusion is based on a low amount of evidence.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 and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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 high for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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 and high-standard farming conditions. Our conclusion is based on a low amount of evidence.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. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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 unclear for minimal and high-standard farming conditions. Our conclusion is based on a low amount of evidence.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 unclear for minimal farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.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 medium for high-standard farming conditions. Our conclusion is based on a low amount of evidence.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 337, level 5 being 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: carnivorous 138 (except for omnivorous FRY stage 139). FARM: replacement of fish meal and fish oil not reported in literature.
Side note: Commercial relevance
How much is this species farmed annually?
Estimated 15 t in 2022 40.
Glossary
ALEVINS = larvae until the end of yolk sac absorption
DOMESTICATION LEVEL 3 = entire life cycle closed in captivity with wild inputs 37
FARM = setting in farming environment or under conditions simulating farming environment in terms of size of facility or number of individuals
FRY = larvae from external feeding on
IND = individuals
JUVENILES = fully developed but immature individuals
LARVAE = hatching to mouth opening
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
WILD = setting in the wild
Bibliography
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