Short profile


FishEthoScore of the species

Abbreviated assessment of the species' likelihood and potential for fish welfare in aquaculture, based on ethological findings for 10 crucial criteria.

Criteria Li Po Ce
1 Home range
2 Depth range
3 Migration
4 Reproduction
5 Aggregation
6 Aggression
7 Substrate
8 Stress
9 Malformation
10 Slaughter
FishEthoScore 0 0 5
Li = Likelihood that the individuals of the species experience welfare under minimal farming conditions
Po = Potential overall potential of the individuals of the species to experience welfare under improved farming conditions
Ce = Certainty of our findings in Likelihood and Potential
 
                    ?     /  
  High    Medium     Low     Unclear  No findings
 
FishEthoScore = Sum of criteria scoring "High" (max. 10)



General remarks

Hippoglossus hippoglossus is a slow growing, cold water flatfish that can reach up to nearly 5 m and over 300 kg. It is endangered due to overfishing. It has a high market value, hence it has been in the focus of the aquaculture industry. However, its particular biology and life history makes this species inadequate to be farmed in welfare. Namely, its home and depth ranges are far greater than any method can satisfy, its reproduction is still largely dependent on invasive induction, it displays aggressive behaviour, requires specific shelter and substrate, and is very sensitive to common farming procedures. In addition due to its slow growth it requires many years of investment, and the metamorphosis in early stages demands extra good rearing conditions in order to produce healthy individuals. Potential for improvement lies principally in providing better conditions for non-induced spawning and proper feeding regimes to avoid aggression.


1. Are minimal farming conditions likely to provide the home range of the species? Is there potential for improvement? How certain are these findings?

L
 Likelihood
L
 Potential
H
 Certainty

LARVAE: WILD: pelagic, planktonic [1]: passive dispersal. FARM: cylindro conical tanks: 700-13,000 L [2] [3]; silos: 15,000 L [2]. LAB: raceways: 1.0 x 0.4 m [4].

JUVENILES: WILD:  large variation in distance covered [2] [5] up to ca 30 km in one day or 100 km in 1 month [6]. FARM: tanks: 5-10 m diameter [7] [8], sometimes 24 m [7]. Sea cages: adapted from salmon [8] [3], max 24 x 24 m or 100 m diameter  [7] [9]. Horizontal shelves are often used  [8] [3] [7].

ADULTS: WILD: >25 km in 7 months [1], median 27 km, max 3141 km in 3 years [5]. FARM: ➝  JUVENILES.

SPAWNERS: WILD: ➝ Adults. FARM: tanks: 5-15 m diameter [7] [3].


2. Are minimal farming conditions likely to provide the depth range of the species? Is there potential for improvement? How certain are these findings?

L
 Likelihood
L
 Potential
H
 Certainty

Eggs: WILD: PELAGIC, planktonic [10] [1]. FARM: cylindro-conical tanks: ca 1 m [2].

LARVAE: WILD: PELAGIC, planktonic [1]. FARM: silos: 4 m [2]; raceways: 0.1-0.2 m [4].

JUVENILES: WILD: benthic  [2], 20 - 60 m [2]. FARM: tanks: ca 1-3 m, cages 3-7 m [3].

ADULTS: WILD: benthic  [2], 250-800 m [1].  FARM: -see Juveniles.

SPAWNERS: BENTHIC  [2]. WILD: below 800 m [1]. FARM: tanks: 1 - 2 m [7] [3].


3. Are minimal farming conditions compatible with the migrating or habitat-changing behaviour of the species? Is there potential for improvement? How certain are these findings?

L
 Likelihood
L
 Potential
M
 Certainty

OCEANODROMOUS [2].

LARVAE: WILD: PELAGIC, planktonic: passive dispersal [10] [2] [1]. FARM: cylindro conical tanks [2] [3], silos [2] or raceways [4]. For details on rearing systems ➝ crit 1 and 2.

JUVENILES: WILD: puberty related migration out of shallower nursery areas [2] [1] into deeper waters [11] [12]. FARM: tanks [7] [8] [7], sea cages adapted from salmon [8] [3] [7] [9]. Horizontal shelves are often used  [8] [3] [7]. 

ADULTS: WILD: usually found on sand, gravel or clay; not on soft mud or on rock bottom [12]. Migrate between forage and spawning grounds [1]. Homing towards repeated spawning spots [13] [13] [14] - [2] [15]. Disperse to several habitats (inshore, offshore, shallower and deeper) after spawning [13] [14] - [2]. FARM: ➝ JUVENILES

SPAWNERS:WILD ➝ Adults. FARM: tanks [7] [3]. For details on rearing systems ➝ crit 1 and 2.


4. Is the species likely to reproduce in captivity without manipulation? Is there potential to allow for it under farming conditions? How certain are these findings?

L
 Likelihood
M
 Potential
H
 Certainty

WILD: Spawns December-March [2] in deep waters over mud or clay substrate [16] [2] [1] at 5-7 ºC [2] [11]. Annual, group-synchronous spawners [11]. FARM: phototermal manipulation [3] and manual stripping are common [3] [17] although natural spawning can occur [18]. Bottlenecks include low supply of quality eggs [17]. Textured substrate in tanks prevent lesions [2].


5. Is the aggregation imposed by minimal farming conditions likely to be compatible with the natural behaviour of the species? Is there potential to allow for it under farming conditions? How certain are these findings?

L
 Likelihood
L
 Potential
H
 Certainty

LARVAE: WILD and FARM: no data found yet.

JUVENILES: WILD: Suggested to be solitary [2]. FARM: flatfish, remain on the bottom hence aggregation measured in kg per unit area. Up to 50-75 kg/m2, ca 10 -13 ind/m2  at preferred harvest weight of 5 kg [3], reared in multiple layers in shelves [8] [3].

ADULTS: ➝ JUVENILES.

SPAWNERS: WILD: data suggests spawning aggregations [2] [19]. FARM: Mostly artificial spawning [8] [3] [17]. Holding tanks for spawners: reccommended 15 kg/m2 [3]. Natural spawning tanks: 17 mature males and 3 mature females in 10 m2 [18].


6. Is the species likely to be non-aggressive and non-territorial? Is there potential for improvement? How certain are these findings?

L
 Likelihood
M
 Potential
L
 Certainty

LARVAE: WILD and FARM: no data found yet.

JUVENILES: WILD: no data found yet. FARM: feeding-related aggression leading to eye injury is common [20] [21] and negatively correlated with size [20]. Proper feeding regimes mitigate the problem [20] [21].

ADULTS: WILD: no data found yet. FARM: aggression decreases as size increases [20].

SPAWNERS: WILD: no data found yet. FARM: no reports of aggression found in the literature.


7. Are minimal farming conditions likely to match the natural substrate and shelter needs of the species? Is there potential for improvement? How certain are these findings?

L
 Likelihood
M
 Potential
H
 Certainty

Eggs: WILD: PELAGIC, planktonic [10] [2] [1]. FARM: aerated cylindro-conical tanks [2].

LARVAE: WILD: see eggs. FARM: require shading for UV protection [22].

JUVENILES: WILD: benthic in deep waters with absence of direct light [2]. FARM: develop skin lesions and papilloma disease in barren, smooth bottom tanks [23]. Sand substrate reduces lesions but increases mortality [21]. Silicone [21] or plastic, irregular substrate [23] improves skin condition. Require shading for UV protection [24].

ADULTS: ➝ JUVENILES.

SPAWNERS: ➝ JUVENILES.


8. Are minimal farming conditions (handling, confinement etc.) likely not to stress the individuals of the species? Is there potential for improvement? How certain are these findings?

L
 Likelihood
M
 Potential
M
 Certainty

Eggs: mechanical stress increases mortality [25].

LARVAE: light (>3 lux) and temperature (>10 ºC) produce mouth abnormalities [26]. Very sensitive to physical stress [27] [28].

JUVENILES: increasing stocking density negatively influences behaviour and growth [19]. Confinement, handling, exercise and tank water level reduction induce stress [7]. Anaesthesia procedure induces stress [29].

ADULTS: ➝ JUVENILES.

SPAWNERS: suggested handling stress associated with female stripping [30].


9. Are malformations of this species likely to be rare under farming conditions? Is there potential for improvement? How certain are these findings?

L
 Likelihood
M
 Potential
M
 Certainty

Eggs: no data found yet.

LARVAE: 17% mouth abnormalities when reared at 2-6º C, 89% when at 10 ºC [26]. 17% deformities when reared in the dark, 35-42 % when reared >3 lux [26]. Supplementation during artemia feeding can decrease problems occuring during metamorphosis [31] [32].

JUVENILES: 41-89% of skeletal abnormalities [33].

ADULTS: no data found yet.


10. Is a humane slaughter protocol likely to be applied under minimal farming conditions? Is there potential for improvement? How certain are these findings?

L
 Likelihood
M
 Potential
M
 Certainty

Common and high-standard slaughter method: a protocol for humane harvesting is available. Stunning is recommended to be performed either by percussion pistol to the head or through electricity (electric fields of 1 V/cm, 50 Hz sinusoidal AC, applied in seawater for durations longer than 10 seconds), followed by immediate bleeding through severing the gill arches [34].


Side note: Domestication

DOMESTICATION LEVEL 3 [35], level 5 being fully domesticated.


Side note: Feeding without components of forage fishery

All age classes: WILD: Carnivorous [2].  FARM: Fish meal may be partly* replaced by non-forage fishery components [36] [37] [38].

*partly = <51% – mostly = 51-99% – completely = 100%


Glossary

ADULTS = mature individuals, for details ➝ Findings 10.1 Ontogenetic development
BENTHIC = living at the bottom of a body of water
DOMESTICATION LEVEL 3 = entire life cycle closed in captivity with wild inputs [35]
FARM = setting in farm environment
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
SPAWNERS = adults that are kept as broodstock
WILD = setting in the wild


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