Version: B | 1.2 (2022-08-15)
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)
Hypophthalmichthys molitrix is one of the four Chinese major carps, together with H. nobilis, Ctenopharyngodon idella, and Mylopharyngodon piceus. This freshwater BENTHOPELAGIC fish naturally occurs in river systems in China and Russia and has been introduced into many countries for aquaculture purposes, despite its apparent great invasion potential and low market price. Together with H. nobilis, it is one of the most intensively cultured fish species in Asia, which is commonly raised in a system of 'harvesting and stocking', that is, stocking at a high density, partial harvesting of the larger FISHES, and the addition of new fingerlings. This Chinese carp, which prefers low flow but not stagnant waters, is commonly raised in polycultures in ponds, pens, reservoirs or lakes. As a plankton feeder, H. molitrix is frequently stocked in ponds for water quality enhancement and as a biocontrol method for phytoplankton. Competition with other species of similar feeding habits in polycultures is expected. H. molitrix is known for leaping out of the water when disturbed, and it naturally breeds during late spring and summer when the water level increases, migrating upstream to spawn. This carp is not able to spawn naturally in ponds or tanks, and its age and size at sexual maturity is apparently very variable and greatly affected by temperature, which means that it can be sold before reaching maturity. H. molitrix is usually kept alive from harvesting to marketing, as it is commonly consumed fresh, so that trucks and boats with water are frequently used as transportation tools. More studies about better slaughtering processes, stress response, and malformations on this species are needed, as well as studies about aggression both in wild and farm conditions. Furthermore, as most of the wild information comes from non-native waters research, more studies are still necessary in native waters.
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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE and FRY: WILD: no data found yet. FARM: FRY: earthen ponds: 600-4,000 m21 2; rectangular ponds: 400 m2 3; rectangular concrete tanks: 20 m2 3; cages in ponds: 0.25 m2 (0.5 x 0.5 m) 2. For carps in general, earthen ponds: 100-1,000 m2 4; tanks: 1.4 m2 (1.2 x 1.2 m) 4. Further research needed to determine whether this applies to H. molitrix as well.
JUVENILES: WILD: no data found yet. FARM: earthen ponds: 100-8,000 m2 5 3 6 7 8 9 10; pens: 360,000 m2 11; floating cages: 1,000 L 5; PVC cylinders in lakes: 1.5 m diameter 9; cages suspended in pig waste treatment systems: 0.6 m3 (0.9 m diameter) 12; enclosures opened to sediment in reservoirs: 100 m2 (10 x 10 m) 13.
ADULTS: WILD: non-native waters: 0.3-10.6 km/day, with maximum daily movement rates of 64 km/day 14, prefer areas of low flow but are never located in areas of 0 m/s 15. FARM: earthen ponds: 8,000 m2 6, 35,000 m2 16 (for ADULTS to become SPAWNERS).
SPAWNERS: WILD: non-native waters: 0.3-10.6 km/day, with maximum daily movement rates of 64 km/day 14. FARM: for ADULTS to become SPAWNERS ➝ ADULTS. Breeding tanks: 1,000-8,000 L 17 16. For carps in general, earthen ponds: 20-30 m or 2,000-25,000 m2 4; storage tanks: 200 m2 (10 x 20 m), 450 m2 (15 x 30 m) 4; breeding tanks: 3.8 m2 (2.5 x 1.5 m), 8 m2 (4 x 2 m), 18.8 m2 (7.5 x 2.5 m), 2 m diameter 4. Further research needed to determine whether this applies to H. molitrix 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 farming conditions. It is medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
Eggs: WILD: no data found yet. FARM: circular hatching tanks: 0.9 m 18.
LARVAE and FRY: WILD: non-native waters: affinity for shallow habitats at the edge of floods 19. FARM: FRY: earthen ponds: 0.9-1.4 m 2; rectangular ponds: 1.0 m 3; rectangular concrete tanks: 0.6 m 3; cages in ponds: 1 m 2. For carps in general, earthen ponds: 0.5-1.2 m 4; tanks: 1.2 m 4. Further research needed to determine whether this applies to H. molitrix as well.
JUVENILES: WILD: caught in artificial dam (mean 34 m, max 108 m) 20 with unclear depth range use. Non-native waters: mean 1.8-4.1 m 21, sampled at 0.6-20.0 m with an increased density with decreasing depth 22. FARM: earthen ponds: 1-2 m 3 6 7 8 9 10; pens: 2 m 11; PVC cylinders in lakes: 1.2 m 9; enclosures opened to sediment in reservoirs: 4 m 13.
ADULTS: WILD: caught in artificial dam (mean 34 m, max 108 m) 20 and reservoirs (13.5-18 m) 23 with unclear depth range use. Non-native waters: mean 1.8-4.1 m, max 9.1 m 14 21, captured at 2.4 m 24 and sampled at 0.6-20.0 m with an increased density with decreasing depth 22. FARM: earthen ponds: 2 m 6, 1.5 m 16 (for ADULTS to become SPAWNERS). For carps in general, earthen ponds: 0.8-2 m 4. Further research needed to determine whether this applies to H. molitrix as well.
SPAWNERS: WILD: non-native waters: mean 1.8-4.1 m, max 9.1 m 14 21, captured at 2.4 m 24. FARM: for ADULTS to become SPAWNERS ➝ ADULTS. For carps in general, earthen ponds: 1.0-2.5 m or deeper depending on climate zone 4; storage tanks: 1.0-1.5 m 4; breeding tanks: 1 m 4. Further research needed to determine whether this applies to H. molitrix 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 and FRY: WILD: 10-14 h PHOTOPERIOD, maximum ~30 °C 27, non-native waters: range 23.8-26.7 °C (summer) 24. FARM: FRY: rectangular ponds or concrete tanks: minimum of 24.5 °C 3; earthen ponds: range 18-23 °C 2; cages in ponds: range 17-29 °C 2. For details of holding systems ➝ crit. 1 and 2.
JUVENILES: WILD: 11-14 h PHOTOPERIOD 27 28 20, minimum ~5 °C (February) and maximum ~31 °C (July-September) 27 20. Non-native waters: 9-16 h PHOTOPERIOD 29, range 2-32.3 °C 30 31 29 24 21 with the lowest degrees in winter and the hottest temperatures during the summer 30 24. Non-native waters: some IND resident, others highly mobile 26 21, annual range 32.4-38.2 km (minimum <0.1 and maximum 347.1 km), most IND have total range sizes <26 km or >102 km 21, site fidelity in lotic waters most of the time, with increased movements in summer probably due to foraging or searching suitable habitats with declining water, average 7-11 km 26. FARM: earthen ponds: range 2.8-34 °C 6 7 8 9; pens: range 12.7-33.6 °C 11; PVC cylinders in lakes: mean 25 °C 9; enclosures opened to sediment in reservoirs: 11-13 h PHOTOPERIOD, 26-31 °C 13. For details of holding systems ➝ crit. 1 and 2.
ADULTS: WILD: ➝ JUVENILES. FARM: earthen ponds: mean 21-21.8 °C (spring-summer) 6. For details of holding systems ➝ crit. 1 and 2.
SPAWNERS: WILD: 11-14 h PHOTOPERIOD 27; maximum ~30 °C 27. Non-native waters: range 8.3-29.6 °C 30 14 24 21. Migrate upstream to spawn 25 32 in spring 26 21: 19-411 km 14 26 and downstream for overwintering: 29-34 km 26, which is triggered by flood pulses 25 32 26 and differences of temperature 26. Some movements in the summer probably from staging areas to protracted spawning events 26. FARM: storage earthen ponds: mean 18-36 °C 17 1; concrete breeding tanks: 23 °C 16. 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 and high-standard farming conditions. Our conclusion is based on a high amount of evidence.
WILD: non-native waters: mature at 2 years old (earlier than in native waters) 33, spawn March-October (spring-autumn), probably can spawn multiple times per year 30. FARM: mature at 2 years old 34; sex ratio 1:1 1 or 1 female:2-3 males 34 4 25. Unable to naturally spawn under artificial conditions like ponds, and induced spawning with hormones is used 25. Attempts to induce spawning by acetone-dried whole carp pituitary for males and together with Human Chorionic Gonadotropin for females followed by stripping in post-spawning season 1 or with mammalian follicle stimulating and luteinising hormones together or not with pituitary gland extract of Cyprinius carpio during the spawning season (no spawn with pituitary gland extract only) 17. Partial success of induced spawning with pituitary extract of Tachysurus thalassinus or T. jella followed by stripping 34. Successful induced spawning by hypophysation 3 or with carp pituitary gland extract followed by stripping and the addition of urea solution to the eggs and milt mixture during natural breeding season 35. Successful induced spawning by Luteinising Release Hormone-Analogue with Pimozide for females and carp pituitary gland for males followed by stripping, despite a higher latency to spawn, a lower number of eggs of good quality, and a higher percentage of deformed larvae than using carp pituitary gland for both sexes 16. For carps in general, in storage tanks, spawners are kept separated by sex 4. Further research needed to determine whether this applies to H. molitrix as well.
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 medium amount of evidence.
LARVAE and FRY: WILD: non-native waters: LARVAE: 10-500 IND/L, depending on the temperature, turbidity, and velocity of the water 24. FARM: FRY: rectangular ponds or concrete tanks: 37 IND/m2 (better growth, but worse survival in tanks) 3; earthen ponds: 12.5-225 IND/m2 25 1 2. For carps in general, earthen ponds: 1,000 IND/m2 for LARVAE in nursery ponds, 12.5-25 IND/m2 for FRY in breeding ponds 4. Further research needed to determine whether this applies to H. molitrix as well.
JUVENILES: WILD: large schools during spawning season 32. Non-native waters: 0.0000005-0.000006 IND/L depending on time of day (higher at night), distance to shore (higher at shoreline), sampling location and season 22. FARM: earthen ponds: 0.05-10 IND/m2 3, polyculture with Hypophthalmichthys nobilis of overall density of 2 IND/m2 9, 0.06-0.4 IND/m2 in polycultures with 1-6 other carps of overall density of 0.1-0.7 IND/m2 5 4 6 10, 0.1 IND/m2 in polyculture with H. nobilis and Ictalurus punctatus of overall density of 2.8 IND/m2 5, 0.03-0.05 IND/m2 in polyculture with 3 other carps and Puntius sophore and Amblypharyngodon mola of overall density of 3.5 IND/m2 8, 1 IND/m2 in polyculture with Oreochromis niloticus and C. carpio of overall density of 2.2 IND/m2 7. Pens: 0.0003-0.04 g/L in polyculture with H. nobilis of overall density of 0.0005-0.06 g/L. Floating cages: 0.03 IND/L in polyculture with H. nobilis of overall density of 0.05 IND/L 5. PVC cylinders in lakes: 2.1 IND/m2 9. Cages suspended in pig waste treatment systems: 0.02 IND/L 12. Mechanically aerated aluminium vessels (transportation): 400 g/L 36. Enclosures opened to sediment in reservoirs: 0,0002 or 0.05 g/L 13. LAB: grouped strongly, forming shoals of about 3 IND and about 6 IND with H. nobilis or, less consistently, about 2 IND with C. carpio 37.
ADULTS: WILD: ➝ JUVENILES. FARM: 0.1 IND/m2 in polyculture with H. nobilis of overall density of 0.2 IND/m2 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 and high-standard farming conditions. Our conclusion is based on a low amount of evidence.
LARVAE and FRY: no data found yet.
JUVENILES: no aggression reported in polyculture with Labeo catla 10, with O. niloticus and C. carpio 7, or with H. nobilis together or not with I. punctatus 5. No aggression reported in polycultures with 3 other carps and P. sophore and A. mola, but H. molitrix affected growth of L. rohita and L. catla probably by competitive interactions for food 8.
ADULTS: no data found yet.
SPAWNERS: no aggression reported in polycultures with other carp species 35.
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: WILD: no data found yet. FARM: for carps in general, double-walled hapa nets (e.g., mosquito netting and whole cloth) to protect from predators 4. Further research needed to determine whether this applies to H. molitrix as well. For details of holding systems ➝ crit. 2.
LARVAE and FRY: WILD: non-native waters: LARVAE: mainly at >123.5 NTU, more frequently at >163 NTU 24. FARM: FRY: rectangular concrete tanks: Secchi disc visibility 0.6 m 3. For details of holding systems ➝ crit. 1 and 2.
JUVENILES: WILD: non-native waters: prefer cobble, but also found in sand and gravel 21, mean 58.5-119.7 NTU 29 24, but increasing turbidity increased stress 29, Secchi disc 0.1-0.5 m 31 29. FARM: earthen ponds: turbid waters during monsoon (transparency: 0.3 m) 8, 9-15 NTU 6, Secchi disc 0.13-0.14 m 7; enclosures opened to sediment in reservoirs: Secchi disc <1 m, with a high fish density increasing the water transparency 13. For details of holding systems ➝ crit. 1 and 2.
ADULTS: WILD: non-native waters: prefer cobble, but also found in sand and gravel 21, mean 58.5-119.7 NTU 29 24, but increased turbidity increased stress 29, Secchi disc 0.1-0.5 m 31 29. Reservoirs in native waters: Secchi disc 2.5 m 23. FARM: earthen ponds: 9-15 NTU 6. For details of holding systems ➝ crit. 1 and 2.
SPAWNERS: WILD: spawn in rivers or tributaries over shallow rapids with gravel or sand bottom 32. Non-native waters: prefer cobble, but also found in sand and gravel 21, mean 59.8-119.7 NTU 24. 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?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 and FRY: WILD and FARM: no data found yet.
JUVENILES: WILD: non-native waters: stress levels change seasonally (less stressed in autumn) 31 29 and are increased by turbidity and density of Dorosoma cepedianum as potential competitors 29. FARM: injuries, mouth deformities, increased mortality by handling due to jumping against the cages of galvanised wire, which could be potentially reduced by less handling, using larger cages and softer material like nylon netting 12. A low-dose of benzocaine or especially of quinaldine decreased stress response and mortality for up to 6 h of transportation in mechanically aerated aluminium vessels 36.
ADULTS: WILD: ➝ JUVENILES. 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?There are unclear findings for minimal and high-standard farming conditions. Our conclusion is based on a low amount of evidence.
LARVAE: WILD: no data found yet. FARM: for carps in general, malformations due to insufficient nutrition 4. Further research needed to determine whether this applies to H. molitrix as well.
JUVENILES: WILD and FARM: no data found yet.
ADULTS: WILD: non-native waters: 2.3% of females with a few abnormally developing oocytes at different stages of maturation (probably sterile), 8% of intersex IND in males and 44% of females with atretic follicles in the pre-spawn stage of reproductive maturation 30. FARM: no data found yet.
SPAWNERS: WILD: non-native waters: 3% of females with atretic follicles in the spawning stage of reproductive maturation 30. 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 low for minimal farming conditions. It is high for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
Common slaughter method: commonly sold live or fresh locally 25, so probably asphyxia. High-standard slaughter method: percussive stunning (one or two blows on the head with a wooden club) followed by scaling, gutting, and filleting is less stressful than immersion in ice or gill cutting followed by the same slaughter procedures 38 39.
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 40, 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: planktonic feeder, mainly on phytoplankton 41 4 25 33 15 28 20 23 but also on zooplankton 41 33 20 23 or detritus 25 33 15, especially in more polluted environments 28. FARM: no additional feed in polyculture 18. Phytoplankton feeder 5 11 13, but can also feed on zooplankton 11 13 (FRY fed on zooplankton and later changed to phytoplankton 2), rarely organic detritus 5. JUVENILES did not accept artificial feed 5 which not affected growth 7 but improved survival in polycultures 7.
BENTHOPELAGIC = living and feeding near the bottom of a body of water, floating above the floor
DOMESTICATION LEVEL 5 = selective breeding programmes are used focusing on specific goals 40
FARM = setting in farming environment or under conditions simulating farming environment in terms of size of facility or number of individuals
FISHES = Using "fishes" instead of "fish" for more than one individual - whether of the same species or not - is inspired by Jonathan Balcombe who proposed this usage in his book "What a fish knows". By referring to a group as "fishes", we acknowledge the individuals with their personalities and needs instead of an anonymous mass of "fish".
FRY = larvae from external feeding on, for details ➝ Findings 10.1 Ontogenetic 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
NTU = Nephelometric Turbidity Units
PHOTOPERIOD = duration of daylight
POTAMODROMOUS = migrating within fresh water
SPAWNERS = adults during the spawning season; in farms: adults that are kept as broodstock
WILD = setting in the wild
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6 Lieberman, D. M. 1996. Use of Silver Carp (Hypophthalmichthys molotrix) and Bighead Carp (Aristichthys nobilis) for Algae Control in a Small Pond: Changes in Water Quality. Journal of Freshwater Ecology 11: 391–397. https://doi.org/10.1080/02705060.1996.9664466.
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16 Brzuska, E. 1999. Artificial spawning of herbivorous fish: use of an LHRH-a to induce ovulation in grass carp Ctenopharyngodon idella (Valenciennes) and silver carp Hypophthalmichthys molitrix (Valenciennes). Aquaculture Research 30: 849–856. https://doi.org/10.1046/j.1365-2109.1999.00413.x.
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25 NOT FOUND
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