Version: B | 1.1 (2021-12-21)
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)
Acipenser baerii, an endangered species according to the IUCN redlist, has been farmed for over a century, but only recently the full life cycle has been successfully closed in aquaculture. Sturgeons are mostly reared for caviar, and while its production started in the former USSR, A. baerii production is now present in Belgium, China, Italy, Germany, Hungary, Poland, Spain, Switzlerland, and the United States of America. However, there are many aspects of welfare that are being overlooked: usual rearing tanks are too small, spawning induction is highly invasive, it requires proper substrate in all stages of its life cycle, and the establishment of a humane slaughter protocol is still missing. Although some effort is being undertaken, fish components are still present in the feed. Many aspects of its biology remain unclear and require further investigation.
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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE: WILD: initially PLANKTONIC, so no home range 1. At 3 days post-hatching with limited movement 1. FARM: hatchery troughs: 50 x 70 cm 2 3; aerated jars: 13-60 L 4 3; LARVAE troughs: 200 x 50 cm 4; FINGERLINGS circular tanks: 2-4 m2 4 3.
ADULTS: WILD: no data found yet. Able to perform large scale movements ➝ crit. 3. FARM: ➝ JUVENILES.
SPAWNERS: WILD: no data found yet. FARM: tanks: 20-40 m2 3; cages: 10-50 m2 3; ponds: 250-1,500 m2 3. For sturgeons in general, pre-spawn holding in "Kazansky" type earthen ponds: 120-130 m 3 or "Kurinsky" type earthen ponds: 30-60 x 12 m 3; long-term holding in concrete tanks: 30-50 m2 3 or cages: 20-100 m2 3; overwintering of breeders in plastic and concrete tanks: >40 m3 3 or "Kurinsky" type concrete ponds: 105 x 17 m or 1,000-4,000 ha separated into different compartments 3. Further research needed to determine whether this applies to A. baerii as well.
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 and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE: WILD: initially PELAGIC 1. At 3 days post hatching become BENTHIC, with limited movement 1. FARM: hatchery troughs: 20-50 cm 2 3; aerated jars: 13-60 L 4 3; LARVAE troughs: 15-20 cm 4; FINGERLINGS circular tanks: ca 1 m 4 3.
JUVENILES: WILD: 20-50 m, occasionally 100-150 m 7. FARM: ponds: 2 m 2; raceways: 0.8-1.5 m 5 6; tanks: 0.6-1.5 m 3; cages: 0.8-2.5 m 3. For sturgeons in general, ponds: 2.3-2.5 m 3; cages: 2.5-3.5 m 3. Further research needed to determine whether this applies to A. baerii as well.
ADULTS: ➝ JUVENILES.
SPAWNERS: WILD: no data found yet. FARM: for sturgeons in general, pre-spawn holding in "Kazansky" type earthen ponds: 0.5-2.5 m 3 or "Kurinsky" type earthen ponds: 1.5-2.5 m 3; long-term holding in concrete tanks: 2 m 3 or cages: 3-3.5 m 3; overwintering of breeders in plastic and concrete tanks: >1.5 m 3. Further research needed to determine whether this applies to A. baerii as well.
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.
LARVAE: WILD: initially PELAGIC, dragged downstream 1. At 3 days post-hatching become BENTHIC and stationary in the bottom 11 1 12. FARM: usually farmed in fresh water 13. For details of holding systems ➝ crit. 1 and 2.
JUVENILES: WILD: some populations stationary in rivers and lakes 14, others migrate to estuaries 15. FARM: usually farmed in fresh water 16 17. Stressed by heat 18. For details of holding systems ➝ crit. 1 and 2.
ADULTS: ➝ JUVENILES.
SPAWNERS: WILD: migrate upstream from lower river basins or estuaries 15 to spawn 19 20 8 21 14. FARM: for sturgeons in general, "Kazansky" or "Kurinsky" type earthen ponds simulate spawning reaches of rivers 3. Further research needed to determine whether this applies to A. baerii as well.
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: spawning in May-June at water temperatures 9-18 °C in the main channel of rivers over stony-gravel or gravelly-sand bottoms near the depressions in which they winter 7. Further research needed on reproductive behaviour. FARM: vernalisation and hormone treatments with gonadotropin-releasing hormone or extracts of sturgeon or carp pituitary to induce ovulation in females 4 3. Eggs are harvested either by repeated abdominal massaging, laparotomy 4 or other surgical techniques 3. Milt is extracted from males through a catheter and a syringe, and insemination is performed manually 3 4. Modern techniques are less invasive and include ultrasound to assess maturity and manual stripping, all under anaesthesia 6.
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?There are unclear findings for minimal farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
ADULTS: WILD: ➝ JUVENILES. FARM: 12-20 kg/m3 6.
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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
JUVENILES: FARM: not aggressive in good farming conditions 6. LAB: the congener A. fulvescens is reported to be non-aggressive 24. Further research needed to determine whether this applies to A. baerii as well.
ADULTS: FARM: not aggressive in good farming conditions 6.
SPAWNERS: FARM: ➝ ADULTS.
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.
LARVAE: WILD and FARM: no data found yet. LAB: use substrate for shelter from 17 days post-hatching onwards 1.
ADULTS: ➝ JUVENILES.
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 low amount of evidence.
Eggs: very sensitive to mechanical stress 13.
LARVAE: ➝ Eggs.
ADULTS: ➝ JUVENILES.
SPAWNERS: stressed by injections but not by confinement 31. Further research needed to disentangle contradictory results.
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 high for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE: malformations in the abdominal cavity, heart, yolk sac walls, skeleton, tail muscles, body trunk, and head structures in 3.6-11.4% of individuals 32 1 33 13 34. High-standard conditions may lower malformation rate to 2-3% 6.
JUVENILES: may incur deformations upon reactions to loud noises or abrupt events (thunders, sudden movements, etc) 6.
ADULTS: ➝ JUVENILES.
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 high 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 5 36, 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)?
*partly = <51% – mostly = 51-99% – completely = 100%
ANADROMOUS = migrating from the sea into fresh water to spawn
BENTHIC = living at the bottom of a body of water, able to rest on the floor
DOMESTICATION LEVEL 5 = selective breeding programmes are used focusing on specific goals 36
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
PELAGIC = living independent of bottom and shore of a body of water
PLANKTONIC = horizontal movement limited to hydrodynamic displacement
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
WILD = setting in the wild
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