For Salmo trutta, a variety of life-history strategies are known. This enhances the adaptability of the species to different environments and explains the success of the species' worldwide introduction. S. trutta populations can be strictly resident or ANADROMOUS, but often populations are partially ANADROMOUS, where a fraction of the populations migrate to the sea, and the other fraction remains resident.

The S. trutta production is insignificant compared to other Salmonidae; generally, production is destined for restocking, recreational fishing, and local consumption (mainly a niche market). In general, there is limited information on current farming conditions making it difficult to assess this species' potential when cultured in captivity. However, some biological aspects such as substrate needs and reproduction without manipulation can be considered welfare limitations to keep this species in captivity. To bridge the lack of information on welfare improvement in this species, the available information in related species such as S. salar may be a good starting point, but needs further research for validation.

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?

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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?

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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?

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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?

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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?

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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?

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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?

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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?

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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?

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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?

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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 523, level 5 being fully domesticated.

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 24. FARM: fish meal and fish oil may be mostly* replaced by non-forage fishery components 2526.

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

How much is this species farmed annually?

3,252 t/year 1990-2019 amounting to estimated 1,000,000-2,000,000 IND/year 1990-2019 27.