Version: B | 1.1 (2022-01-22)
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
FishEthoScore = Sum of criteria scoring "High" (max. 10)
Rachycentron canadum is a migratory pelagic species widely distributed in subtropical, tropical, and temperate areas, except for the central and eastern Pacific. Several biological attributes make R. canadum a strong candidate for aquaculture, such as rapid growth, high fillet quality, and high market price. However, many aspects of welfare in rearing conditions have not been addressed yet. In order to optimise fish welfare of this species, improvements in current harvesting practices are needed to meet depth range needs, reproduction without manipulation, aggregation, aggression, and stress reduction.
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.
LARVAE: WILD: no data found yet. FARM: circular tanks: 3.6 m diameter 1, 12 m3 2; ponds: <5,000 m2 3.
JUVENILES: WILD: no data found yet. FARM: FINGERLINGS nursery ponds: >300 m2 3, FINGERLINGS nursery nets: 600 m3 4; wooden cages: 3 x 3 m 5; circular cages: 300-1,800 m3 (8-16 m diameter) 3 5; trapezoidal-octagon shaped cages: 20-30 m cross-section 4.
ADULTS: WILD: no data found yet. FARM: ➝ JUVENILES.
SPAWNERS: WILD: no data found yet. FARM: tanks: 7.5 x 4.5 m 6, 60-80 m3 1 2; ponds: 400-600 m2 3 5.
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 medium for high-standard farming conditions. Our conclusion is based on a high amount of evidence.
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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
OCEANODROMOUS 13 8 7 9 14 15 16 17. EURYHALINE 4.
LARVAE: WILD: PELAGIC 7 14 15 16. Based on distribution in tropical, subtropical, and warm-tempered water 7, estimated 9-15 h PHOTOPERIOD; 18.8-28.8 °C 11, 28-32 °C 2, 20.1-30.0 °C 17, 28.4-34.3 psu 17. FARM: tanks: 28.7-30.1 °C 1, 28-32 °C 2. For details of holding systems ➝ crit. 1 and 2.
JUVENILES: WILD: based on distribution in tropical, subtropical, and warm-tempered water 7, estimated 9-15 h PHOTOPERIOD; 18.8-28.8 °C 11, 28-32 °C 2, 20.1-30.0 °C 17, 28.4-34.3 psu 17. In the western Atlantic, migrate inshore in May and leave in autumn to overwintering grounds 18 9. FARM: sea-cages: grow-out takes longer in regions with temperatures down to 16 °C compared to regions with 23.5-28 °C (≤17 versus 11-14 months) 3. For details of holding systems ➝ crit. 1 and 2.
ADULTS: ➝ JUVENILES.
SPAWNERS: WILD: spawning in offshore waters 13 19 20 or inshore 13 18 17. FARM: tanks: 24-30 °C 1, 24-26 °C 2. 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?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.
WILD: mature at 2-3 years 18 9, spawn April-September 13 18 21 9 22 17 possibly multiple times 18. FARM: 1:2 female:male ratio 2. Simulated natural PHOTOPERIOD and temperature regime induces natural spawning 23 6 24 2. Hormonal stimulation to induce ovulation and spermiation 25 23 24. Spawning tanks with egg collectors 23 6 24.
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 and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE: WILD: no data found yet. FARM: intensive conditions RAS: 30-50 IND/L 5; extensive conditions: 5-10 IND/L 1 2.
JUVENILES: WILD: live solitary or in small groups of 3-4 26 7. FARM: FINGERLINGS nursery nets: 13.3-23.3 IND/m3; grow-out cages: 2-3 kg/m3 2, 2.9-5.2 IND/m3 4; offshore cages: 5-15 kg/m3 3 1.
ADULTS: ➝ JUVENILES.
SPAWNERS: WILD: form spawning aggregations 18 7 17. FARM: ponds: 100 IND/400-600 m2 3; tanks: 1-2 kg/m3 1.
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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
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 high for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
Eggs and LARVAE: PELAGIC 7. FARM: for details of holding systems ➝ crit. 1 and 2.
JUVENILES: WILD: often seen in the vicinity of buoys, fishing piers and over artificial reefs 9, caught over bottom with mud, rock, gravel, sand 11. FARM: ➝ LARVAE.
ADULTS: WILD: ➝ JUVENILES. FARM: ➝ LARVAE.
SPAWNERS: WILD: ➝ LARVAE. FARM: tank covered 95% with cloth for shading 2. 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?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.
LARVAE: no data found yet.
JUVENILES: stressed by air exposure 34 35, water acidification 36 and during transport 3 37. For stress and temperature ➝ crit. 3.
ADULTS: stressed by air exposure 34 35, water acidification 36, limited space 38 and during transport 3 37. For stress and temperature ➝ crit. 3.
SPAWNERS: 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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
LARVAE: malformations of jaw 28. Further research needed on frequency of malformations.
JUVENILES: malformations of jaw, operculum, and vertebral column 12 39. Further research needed on frequency of malformations.
ADULTS: malformations of jaw, operculum, vertebral column 12 39, and gonads 40. Further research needed on frequency of malformations.
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 medium 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 4 46, 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 9 47. FARM: fish meal and fish oil may be partly* replaced by non-forage fishery components 48 49 50 51 52.
*partly = <51% – mostly = 51-99% – completely = 100%
DOMESTICATION LEVEL 4 = entire life cycle closed in captivity without wild inputs 46
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
FINGERLINGS = early juveniles with fully developed scales and working fins, the size of a human finger; for details ➝ Findings 10.1 Ontogentic development
IND = individuals
JUVENILES = fully developed but immature individuals, for details ➝ Findings 10.1 Ontogenetic development
LAB = setting in laboratory environment
LARVAE = hatching to mouth opening, for details ➝ Findings 10.1 Ontogenetic development
OCEANODROMOUS = living and migrating in the sea
PELAGIC = living independent of bottom and shore of a body of water
PHOTOPERIOD = duration of daylight
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
WILD = setting in the wild
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