Version: B | 1.4 (2022-07-20)
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)
Dentex dentex is a sparid commonly found on the Mediterranean coast. Due to its higher growth rate in captivity compared to the existing cultured Mediterranean species it is considered a great potential for the diversification of the European aquaculture industry. Nevertheless, there are several biological aspects, such as high mortality levels due to sensitivity to handling and aggressive behaviour in early life stages, that need urgent attention. This may be related to the rearing protocols and techniques for the cultivation of this species. Normally, the same protocols are used as in Sparus aurata and Dicentrarchus labrax. Thus, the limited information about this species on wild and farming conditions are serious bottlenecks to optimising fish welfare in rearing conditions, in particular related to stress susceptibility and aggressive behaviour.
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.
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.
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?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.
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.
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: WILD: no data found yet. FARM: tanks: 40-50 IND/L 10.
JUVENILES: WILD: schools 6 5. Further research needed on extent of schools. FARM: no data found yet.
ADULTS: WILD: solitary 11 6 5. FARM: no data found yet.
SPAWNERS: WILD: spawning aggregations 7 6 5. FARM: no data found yet. LAB: 3 kg/m3 3.
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 and high-standard farming conditions. Our conclusion is based on a low 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 medium for high-standard farming conditions. Our conclusion is based on a medium amount of evidence.
LARVAE: WILD and FARM: no data found yet.
JUVENILES: WILD: usually found on rocky, rubble bottoms and Posidonia oceanica beds 7 13 14. FARM: for details of holding systems ➝ crit. 1 and 2. Tanks and sea cages usually without substrate.
ADULTS: ➝ JUVENILES.
SPAWNERS: WILD: no data found yet. FARM: for details of holding systems ➝ crit. 1 and 2. Tanks usually without substrate.
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.
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 high amount of evidence.
LARVAE: WILD: no skeletal deformations 18. FARM: semi-extensive: skeletal deformations in 4-15%; extensive: skeletal deformations in 25-26% 18. Intensive rearing: skeletal deformations in 82%, mesocosmos: skeletal deformations in 45% 8.
JUVENILES: WILD and FARM: no data found yet.
ADULTS: WILD and FARM: no data found.
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: for the related Sparus aurata, immersion in ice-water 19. High-standard slaughter method: for Dicentrarchus labrax and S. aurata, other popular Mediterranean aquaculture species, humane slaughter protocol available 20. Further research needed to determine whether these apply to D. dentex 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 4 21, 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 22 7. FARM: fish meal and fish oil may be partly* replaced by non-forage fishery components 23 24 25.
*partly = <51% – mostly = 51-99% – completely = 100%
BENTHOPELAGIC = living and feeding near the bottom of a body of water, floating above the floor
DOMESTICATION LEVEL 4 = entire life cycle closed in captivity without wild inputs 21
FARM = setting in farming environment or under conditions simulating farming environment in terms of size of facility or number of individuals
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
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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