Version: B | 1.3 (2022-09-18)
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)
Tachysurus sinensis is a nocturnal catfish that lives in China, Laos, Vietnam, Korea, Japan, India, and Russia and has been introduced in Germany. It is cultured mostly in China, but also in Southeast Asia, and is consumed in China and other Asian countries such as Japan and South Korea. T. sinensis reaches marketable size at 2 years (first year as fingerlings/juveniles, another 8 months of growth in the second year until market size). It is sometimes polycultured with Erythroculter ilishaeformis. Males grow 30% faster than females and reach bigger sizes, and so the farming industry tried to focus on creating a breed of only males. There are many types of breeding technologies available for this species: selective breeding of broodstock from natural waters, cross‐breeding with other species such as Pelteobagrus vachelli, cell and genetic engineering breeding (which generates an all-male breed), and molecular marker‐assisted breeding. However, there is little information available about their breeding behaviour, other than males provide parental care, and so natural breeding is not performed in farms. There is no information about migratory patterns, which could mean that there are none, however, further research is needed to confirm this hypothesis. There is also a lack of information about their social behaviour, including aggregation and aggressiveness, about the situations that cause them stress, and about the level of malformations found in farms. Stunning and slaughtering protocols are not developed yet for T. sinensis, but there are available high-standard methods for other catfish species that could be studied in T. sinensis. In general, more research needs to be carried out in order to establish the biological needs of T. sinensis.
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 low amount of evidence.
LARVAE and FRY: WILD: no data found yet. FARM: ponds: ≥0.5-2.1 ha 1; cages 2 1 in lakes, rivers, and reservoirs 1: 25 m2 (5 x 5 m).
JUVENILES: WILD: no data found yet. FARM: ponds: ≥3-5 ha 1; in-pond raceways: 110 m2 (22 x 5 m) 3; cages 2 1 in lakes, rivers, and reservoirs 1: 25 m2 (5 x 5 m).
ADULTS: WILD: in rivers 4-5-6, lakes 7 4-5-6, channels 4-5-6 and large reservoirs 7. FARM: ponds 2 1: ≥3-5 ha 1; in-pond raceways: 110 m2 (22 x 5 m) 3; earthen ponds 8; cages 2 1 in lakes, rivers, and reservoirs 1: 25 m2 (5 x 5 m); pond polyculture 2 1; cage polyculture 1; culture-based fisheries 2; ponds with circulating water channels 1.
SPAWNERS: WILD: no data found yet. FARM: tanks: 500 L 9; indoor spawning pools: 4 m2 (2 x 2 m) 1.
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 high for minimal and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE and FRY: WILD: no data found yet. FARM: ponds: 0.2-0.3 m 1; cages: 2.5-3 m 1.
JUVENILES: WILD: DEMERSAL 10; 2.6 m 10. FARM: ponds: 1.5-2 m 1; cages: 2.5-3 m 1; in-pond raceways: 2 m 3.
ADULTS: WILD: ➝ JUVENILES. FARM: ponds: 2-3 m 1; cages: 2.5-3 m 1; in-pond raceways: 2 m 3.
SPAWNERS: WILD: 0.2-1 m 11. FARM: ponds: water level controlled 1; indoor spawning pools: 1.5 m 1.
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 high for high-standard farming conditions. Our conclusion is based on a low amount of evidence.
All age classes: WILD: nocturnal (feeding) behaviour 7. Based on distribution (➝ General remarks), estimated 8-17 h PHOTOPERIOD, fresh water. FARM: for details of holding systems ➝ crit. 1 and 2. LARVAE and FRY: high survival and growth in dark blue and black tanks, moderate stress and survival in white tanks, and high stress and low survival in green and maroon tanks 14.
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 and high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
WILD: mature at age 1+ 15, although in some populations spawn at 0+ 5-15 and 2+ and 3+ 16-15. Spawns once a year 15. Spawning season April-August, with two spawning peaks: one in May and a smaller one in July-August 15. Water temperature: 23-30 °C 15. In simulated data: spawns in June-July during 3 days, in riverbeds, at 23-30 °C (optimal temperature: 22-25 °C) 11. Population sex ratio: 1.08 female:male 15. Group sex ratio: 1.14:1 female:male, which goes to 1.74 in spawning peak month 15. Sex ratio variation among populations 15. Male parental care 4-17. FARM: oxytocin injections to induce maturation 1. Hormonal manipulation to induce spawning 18-1 7 9, without stripping and with undisturbed fertilisation at sex ratio 1:1 or 1:1.5 female:male, stimulated by running water 1. Hormonal manipulation with female stripping at sex ratio 4:1 male:female 1, male testes removed, eggs and sperm mixed manually 1 7 9. Artificial incubation 1. Water temperature manipulation to promote earlier maturation 1. Males: ≥180 g; females: ≥120 g 1.
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 and high-standard farming conditions. Our conclusion is based on a low amount of evidence.
LARVAE and FRY: WILD no data found yet. FARM: cages: 2,000-3,000 IND/m2 1; ponds: 1.0-1.5 million IND/ha; soft-shelled turtle co-culture ponds: 3,000 IND/ha of 5g IND 2. High stocking densities 1.
JUVENILES: WILD: no data found yet. FARM: cages: 1,000-1,500 IND/m2 1; soft-shelled turtle co-culture ponds: 3,000 IND/ha 2; in-pond raceways: 4.4 kg/m3 3; high stocking densities 1.
ADULTS: WILD: no data found yet. FARM: cages: 500-600 IND/m2 1; soft-shelled turtle co-culture ponds: 3000 IND/ha 2; 10-15 IND/m2 1; in-pond raceways: 4.4 kg/m3 3; high stocking densities 1.
SPAWNERS: WILD: aggregations during spawning and nesting 4-5-6. FARM: no data found yet.
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 no findings for minimal and high-standard farming conditions.
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 and FRY: WILD: no data found yet. FARM: ponds with flat substrate 1, sediment thickness 15-30 cm 1; weed-free ponds and perimeter 1; crops can be planted on pond edges (1-1.5 m) to provide fish food and shelter 1.
JUVENILES: WILD: DEMERSAL 1. Sand, gravel, rubble, preference for mud bottom with aquatic weed 7. Nutrient-rich clay sediment, with small herbaceous species 15. Prefer clear water but does well in muddy water 7. FARM: ponds with flat substrate 1; weed-free ponds and perimeter 1.
ADULTS: WILD: ➝ JUVENILES. FARM: weed-free ponds and perimeter 1; biological floating beds 1.
SPAWNERS: WILD: in riverbeds 11. Males make burrow nests on even river sandy shallow areas free or almost free from vegetation 19-20 and in clayey soil 4-6. FARM: spawning stimulation by slow water flow 1.
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.
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 no findings for minimal and high-standard farming conditions.
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 low amount of evidence.
Common slaughter method: no stunning method available 21; by 2018 only available in the market as live fish 1; by 2018 there was no processing company in China 1. Further research needed to determine whether the situation has changed since then. High-standard slaughter method: for the related Clarias gariepinus, a) stunning with captive pistol (8 bar pressure) and chilling in icewater 22, b) dry electro-stunning (0.76 A, 150 V, AC+DC for 15 s) followed by chilling and decapitation 23 or c) freshwater electro-stunning (1.60 ± 0.11 A/dm2, 50 Hz, sinusoidal, A.C., conductivity of 876 μS) followed by chilling and decapitation 24. Further research needed to determine whether this applies to T. sinensis as well.
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 2 25, 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: omnivorous 2 1; insectivorous 10. FARM: fish meal and fish oil may be partly* replaced by sustainable sources 26 27, but no data found yet for ADULTS and SPAWNERS.
partly = <51% – mostly = 51-99% – completely = 100%
DEMERSAL = living and feeding on or near the bottom of a body of water, mostly benthopelagic, some benthic
DOMESTICATION LEVEL 2 = part of the life cycle closed in captivity, also known as capture-based aquaculture 25
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
IND = individuals
JUVENILES = fully developed but immature individuals, for details ➝ Findings 10.1 Ontogenetic development
LARVAE = hatching to mouth opening, for details ➝ Findings 10.1 Ontogenetic development
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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