Version: B | 1.1 (2022-07-20)
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)
Oncorhynchus tshawytscha is a Pacific salmon species distributed from northern Hokkaido to the Anadyr River on the Asian coast and from central California to Kotzebue Sound, Alaska, on the North American coast. Two morphotypes have been described, a "spring/stream" type that remains in the streams for a year and an "fall/ocean" type that migrates to the ocean a few weeks after hatching. O. tshawytscha is anadromous: eggs hatch in streams, juveniles (parr) live in streams for one or two years or a few weeks before migrating to the ocean. In the ocean, smolts grow into adults and either stay at the coast or migrate mostly up north. When they are close to maturity, they migrate back to their original streams to spawn in the autumn, independently of when they enter the stream. Females create several nests in a defended area called redd. O. tshawytscha dies after reproduction. Triploid breeds can be used to avoid the reproductive stage in farms. Because of their need to migrate as adults, it is unlikely that current farms can provide this welfare need. Further research needs to be done to accommodate this need into farming conditions and on living offshore (home range, aggregation, aggression, substrate). O. tshawytscha was successfully transplanted in New Zealand in the late 1800s, and nowadays New Zealand is the major exporting country of O. tshawytscha. Some populations in the USA are listed as endangered or threatened.
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?There are unclear findings for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
ADULTS: WILD: no data found yet. FARM: raceways: 90 m2 (30 x 3 m) 1; ocean pens 3; sea cages 2: 216 m3 4, 6,000 m3 4, 9,000 m3 5 6; RAS: 5-25 m3 tanks 2; outside concrete raceways and ponds 7 (for ADULTS to become SPAWNERS).
SPAWNERS: WILD: redds: 14.7-18.2 m2 8, 1.2-9.1 m diameter 9; spring-runs: 6.5 m2, summer-runs: 3.9 m2, fall-runs: 4.8-5.4 m2 10. Nests: 0.9-1.2 m 11. FARM: for ADULTS to become SPAWNERS ➝ ADULTS. Holding pens in ponds: 7.4 m2 (3.1 x 2.4 m) 12; tanks: 20,000 L, 40,000 L, 70,000 L 2.
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?There are unclear findings for minimal and high-standard farming conditions. Our conclusion is based on a low amount of evidence.
ALEVINS: WILD and FARM: no data found yet.
SMOLTS: WILD and FARM: no data found yet.
ADULTS: WILD: >36 m 14. FARM: no data found yet.
Some species undergo seasonal changes of environments for different purposes (feeding, spawning, etc.) and with them, environmental parameters (photoperiod, temperature, salinity) may change, too.
What is the probability of providing farming conditions that are compatible with the migrating or habitat-changing behaviour of the species?It is low for minimal and high-standard farming conditions. Our conclusion is based on a high amount of evidence.
ALEVINS and FRY: WILD: minority (stream-type, 28.4% 18) remains in streams 19. Majority (ocean-type, 71.6% 18) leaves streams a few weeks post hatching 19, 30% go to estuaries (the fate of the other 70% is unknown) 15 in March-May 17 20 (40 mm fork length, 0.5 g 20). FARM: fresh water 1 2. For details of holding systems ➝ crit. 1. LAB: can handle 15-25 ppm saltwater depending on size 16.
PARR: WILD: stream-typ: in streams 15, ocean-type: not applicable. FARM: ➝ ALEVINS and FRY.
SMOLTS: WILD: stream-type: migration to estuaries either in May-June as first year fingerling smolt (60-80 mm fork length, 2-5 g) or in April-May as second year yearling-smolt (80-110 mm, 5-18 g) 20. Migrate to sea in the first year and remain by the coast 20. Ocean-type: at 70 mm, migrate from estuaries into the ocean 20. In the ocean, migrate away from the coast 20 mostly northwards, rarely southwards 18. FARM: fresh water 1 or transferred to ocean pens 3 or sea cages 2.
SPAWNERS: WILD: travel ≤3,200 km upstream 22-15 23-15 in large water streams >5 m wide 24, 4.3-9.6 km/day 25 in Feb-Dec 26 with peaks that vary depending on latitude (reviewed in 15). Stream-types enter streams mostly in spring 21 27, spawning upstream in the autumn 28-11; ocean-types enter streams in summer-autumn 27, spawning downstream in the autumn 28-11. No natural reproduction observed in population stocked into lake outside of natural distribution, probably due to higher temperature and turbidity 29-30. 6-20 h PHOTOPERIOD, range 9.3-23.2 °C, fresh water, but hints of stress ≥18 °C 31. FARM: for details of holding systems ➝ crit. 1 and 2.
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 theses circumstances?It is low for minimal farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a high amount of evidence.
WILD: males spawn at year 4 or 5 19, some (called GRILSE or "jack") earlier (year 2) 19; females mature at year 4+ 19. Spawning in autumn 32, independent of season of entry in the run 11 15, July-Sept at higher latitudes and Nov-Jan in lower latitudes 15. No feeding after entering fresh water and atrophy of the digestive system before spawning 21 33. Sex ratio: 2.1 males:1 female 11, spawn in pairs with <10-12 extra males attending and releasing sperm 34-35. For aggressive behaviour ➝ crit. 6, for nest building ➝ crit. 7. In artificial stream: male courts female 32. Females' health deteriorates after spawning but they keep digging false nests until they die (2-4 weeks); males continue courting even with own physical deterioration 11. FARM: captively-reared males and females naturally reproduced when put in an artificial stream mimicking natural conditions 1. In spawning stations 30 and hatcheries 7, eggs can be pneumatically expelled from ripe females using compressed oxygen at low pressure 30 or surgically extracted after humane killing 7, milt collected from live males and added to eggs 7 30. Induced ovulation by hormonal treatment 12. Delayed maturation by PHOTOPERIOD manipulation 7. Triploid fish are used to avoid reproductive stage 36.
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 low for minimal farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
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?There are unclear findings for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
ALEVINS: WILD and FARM: no data found yet. LAB: stream-type more aggressive than ocean-typein groups of 16 each 38.
PARR: WILD: ocean-type: nipping, lateral display, chasing, fleeing 37, in groups of 50 in observations troughs alongside stream: also fighting, submission, and redirected aggression 37. null: no data found yet. LAB: lower aggression during feeding in triploid than in diploid IND 36.
SMOLTS: WILD and FARM: no data found yet.
ADULTS: WILD and FARM: no data found yet.
SPAWNERS: WILD: females defend redds and ≤6 m around from females only and can seriously injure the intruders 11. Males fight for spawning participation but not as aggressively as females defending their territory 11. In artificial stream: males aggressive towards females in unselected pair context 32. FARM: no data found yet.
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).
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.
Eggs and ALEVINS: WILD: heavy sedimentation increases eggs mortality 35. Mean 19 cm gravel depth 8. Negatively phototactic and positively geotactic and thigmotactic, they submerge into gravel 39-35 for 1+ month(s) 39-35. FARM: for details of holding systems ➝ crit. 1.
SMOLTS: WILD: in estuaries and at sea 20. FARM: ➝ Eggs and ALEVINS.
ADULTS: WILD: at sea 15. FARM: ➝ Eggs and ALEVINS.
SPAWNERS: WILD: in artificial stream: females dig up ~4 nests and cover eggs after oviposition and fertilisation by males 32. Redds mean gravel size 10.7 cm 11; gravel mostly mix of 7.5-15 cm and <7.5 cm but larger than heavy sand, but also up to 41% of >15 cm gravel 10. FARM: for details of holding systems ➝ crit. 1 and 2.
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?There are unclear findings for minimal and high-standard farming conditions. Our conclusion is based on a low amount of evidence.
ALEVINS: FARM: no data found yet.
PARR: FARM: stressed by coded-wire-tagging, counting, ventral fin clipping, adipose fin clipping, a simulated pond split procedure 43 and (repetitive) handling 44. LAB: stressed by simulated transportation 40.
SMOLTS: FARM: no data found yet.
ADULTS: FARM: no data found yet.
SPAWNERS: FARM: no data found yet.
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 low for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
ALEVINS: WILD: no data found yet. FARM: lordosis, kyphosis, bent tail/neck, tail/spine malformation when reared at 4, 8, and 12 °C in 0.1-16.2%, with lowest frequency at 8 °C 45. Internal malformations even when normal external phenotype, with highest prevalence (40%) in 4 °C group and lowest (16%) in 8 °C group 45.
PARR: WILD and FARM: no data found yet.
SMOLTS: WILD: no data found yet. FARM: one or more of vertebral fusions in 1.2-4.4% at transfer to sea pens, in 7.6-9.0% after 1-1.5 year in sea pens 6. Vertebral deformities in 8.8% after 0.5 year in sea pens, in 38.4% after 1 year in sea pens (76.5% lordosis/kyphosis/scoliosis, 19.9% fusion, 8.4% compression of vertebrae or intervertebral space) 5. Lordosis/kyphosis/scoliosis in 5.4% after 1 month in sea pens, in 39.7-43.0% after 1 year in sea pens 4.
ADULTS: WILD and FARM: no data found yet.
SPAWNERS: WILD: one or more of vertebral deformities (lordosis/kyphosis/scoliosis, fusion, compression, vertical shift) with mostly low severity in 88.1% 46. FARM: no data found yet.
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 high for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
Common and high-standard slaughter method: blow to the head, then bled by cutting gill arches 7. Anaesthetised and overdosed with AQUI-STM (Aqui‐S New Zealand Ltd.) (based on eugenol as active ingredient) 47 6 or anaesthetised with AQUI-S followed by percussive stunning and bleeding 4. For the related O. mykiss, indications that electrical stunning before killing by chilling or bleeding are most effective 48 49 50 51. Further research needed to determine whether this applies to O. tshawytscha as well 52.
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 5 53, 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 15 20. FARM: fish meal may be partly* replaced by sustainable 54 55 or non-forage fishery components 56 or mostly* replaced by non-forage fishery components 57, and fish oil may be mostly* 58 to completely* replaced by sustainable sources 59 60, but no data found yet for ADULTS and SPAWNERS. Inclusion of soybean meal may lead to intestinal inflammation 61.
* partly = <51% – mostly = 51-99% – completely = 100%
ALEVINS = larvae until the end of yolk sac absorption, for details ➝ Findings 10.1 Ontogenetic development
ANADROMOUS = migrating from the sea into fresh water to spawn
DOMESTICATION LEVEL 5 = selective breeding programmes are used focusing on specific goals 53
EURYHALINE = tolerant of a wide range of salinities
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, for details ➝ Findings 10.1 Ontogenetic development
GRILSE = adults returning from sea to home river to spawn, for details ➝ Findings 10.1 Ontogenetic development
IND = individuals
LAB = setting in laboratory environment
PARR = juvenile stage in rivers, for details ➝ Findings 10.1 Ontogenetic development
PHOTOPERIOD = duration of daylight
SMOLTS = juvenile stage migrating to the sea, for details ➝ Findings 10.1 Ontogenetic development
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
WILD = setting in the wild
null = setting in farm environment
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10 NOT FOUND
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