Finding optimal conditions for Yellowtail Kingfish by Jonathan Roques
The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption a... more The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 +/- 0.6 g) were kept for 29 days at 14, 18,
22, 26 (experimental) and 30 g L-1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L-1 (7.61 +/- 0.19,
7.61 +/- 0.01 and 7.61 +/- 0.13% day-1, respectively)
had higher growth rates than fish at 26 and 30 g L-1 (7.10 +/- 0.05 and 6.97 +/- 0.06% day-1 respectively). The higher growth rate at
lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture
species.
Aquaculture, 2012
A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in ... more A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in the Netherlands identified yellowtail kingfish Seriola lalandi as having excellent potential. To assist in determining the most appropriate water quality conditions for this species in RAS, the effect of water temperature (21, 23.5, 25, 26.5 and 29 °C) and pH (6.58, 7.16 and 7.85) was tested in two separate experiments. Growth performance, feed conversion, stress-physiological and metabolic parameters were assessed in juvenile yellowtail kingfish grown in pilot-scale RAS. Growth was optimised at a water temperature of 26.5 °C, in
combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21 °C to 26.5 °C resulted in a 54% increase in the fish's final weight after 30 days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish
could not adapt.
Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a re... more Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a recirculating aquaculture system. Therefore, optimal swimming speeds (Uopt in m s-1 or body lengths s-1, BL s-1) were assessed and then applied to determine the effects of long-term forced and sustained swimming at Uopt on growth performance of juvenile yellowtail kingfish. Uopt was quantified in Blazka-type swim-tunnels for 145 mm, 206 mm and 311 mm juveniles resulting in values of: 1) 0.70 m s-1 or 4.83 BL s-1, 2) 0.82 m s-1 or 3.25 BL s-1 and 3) 0.85 m s-1 or 2.73 BL s-1. Combined with literature data from larger fish, a relation of Uopt (BL s-1) = 234.07(BL)-0.779 (R2= 0.9909) was established for this species. Yellowtail kingfish, either forced to perform sustained swimming exercise at an optimal speed of 2.46 BL s-1 (‘swimmers’) or allowed to perform spontaneous activity at low water flow (‘resters’) in a newly designed 3,600 L oval flume (with flow created by an impeller driven by an electric motor), were then compared. At the start of the experiment, ten fish were sampled representing the initial condition. After 18 days, swimmers (n= 23) showed a 92% greater increase in BL and 46% greater increase in BW as compared to resters (n= 23). As both groups were fed equal rations, feed conversion ratio (FCR) for swimmers was 1.21 vs. 1.74 for resters. Doppler ultrasound imaging showed a statistically significant higher blood flow (31%) in the ventral aorta of swimmers vs. resters (44 ± 3 mL min-1 vs. 34 ± 3 mL min-1, respectively, under anesthesia). Thus growth performance can be rapidly improved by optimal swimming, without larger feed investments.
Aquaculture, 2012
A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in ... more A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in the Netherlands identified yellowtail kingfish Seriola lalandi as having excellent potential. To assist in determining the most appropriate water quality conditions for this species in RAS, the effect of water temperature (21, 23.5, 25, 26.5 and 29 °C) and pH (6.58, 7.16 and 7.85) was tested in two separate experiments. Growth performance, feed conversion, stress-physiological and metabolic parameters were assessed in juvenile yellowtail kingfish grown in pilot-scale RAS. Growth was optimised at a water temperature of 26.5 °C, in combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21 °C to 26.5 °C resulted in a 54% increase in the fish's final weight after 30 days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish could not adapt
Aquaculture Research, 2014
The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption a... more The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 AE 0.6 g) were kept for 29 days at 14, 18, 22, 26 (experimental) and 30 g L À1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L À1 (7.61 AE 0.19, 7.61 AE 0.01 and 7.61 AE 0.13% day À1 , respectively) had higher growth rates than fish at 26 and 30 g L À1 (7.10 AE 0.05 and 6.97 AE 0.06% day À1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.
Nociception and pain in fish by Jonathan Roques
Fish Physiology and Biochemistry, 2012
Consumer awareness of the need to improve fish welfare is increasing. Electrostunning is a clean ... more Consumer awareness of the need to improve fish welfare is increasing. Electrostunning is a clean and potentially efficient procedure more and more used to provoke loss of consciousness prior to killing or slaughtering (reviewed by Van de Vis et al. in Aquac Res 34:211–220, 2003). Little is known how (powerful)
electrical stimuli, which do not stun immediately, are perceived by fish. We investigated responses of handheld Mozambique tilapia (Oreochromismossambicus) to a standardized electric shock applied to the tailfin. The handling with the resulting unavoidable acute stress response was carefully controlled for. Fish responses
were analyzed up to 24 h following the shock. Electric shock resulted in slightly higher levels in plasma cortisol, lactate, ionic levels, and osmolality, than handling alone. Plasma glucose had significantly increased 6 h after shock compared to handling, indicative of enhanced adrenergic activity. Mucus release from the gills, branchial Na+/K+ ATPase activity, and chloride cell migration and proliferation, parameters that will change with
strong adrenergic activation, were not affected. Decreased swimming activity and delay in resumption of chafing behavior indicated a stronger and differential response toward the electric shock. Responses to handling lasted shorter compared to those to an electric shock. The differential and stronger responses to the electric shock suggest that fish perceived the shock
potentially as painful.
Physiology & Behavior, 2010
The fish welfare debate is intensifying. Consequently, more research is carried out to further ou... more The fish welfare debate is intensifying. Consequently, more research is carried out to further our knowledge on fish welfare in aquaculture. We define here a series of key parameters to substantiate an acute response to a supposedly painful stimulus: a standardized tailfin clip.Ultrastructural analysis of common carp (Cyprinus carpio) tailfin indicates the presence of A-δ and C-type axons, which are typical for transmitting nociceptive signals in (higher) vertebrates. In Nile tilapia (Oreochromis niloticus), responses to a tailfin clip were studied and the unavoidable acute stress associated with the handling required for this procedure. A series of key parameters for further studies was defined. The responses seen in ‘classical’ stress parameters (e.g., changes in plasma cortisol, glucose and lactate levels) did not allow discrimination between the clipping procedure and the handling stress. However, three parameters indicated a differential, stronger response to the clip stimulus itself: first, swimming activity increased more and clipped fish spent more time in the light (in a tank where half the volume is covered by dark material); second, the gill's mucus cells released their content as observed 1 h after the clip, and this response is transient (no longer observed at 6 h post clipping). Third, branchial Na+/K+-ATPase activity assayed in vitro was not affected by the procedures, but a remarkable migration of Na+/K+-ATPase immunoreactive (chloride) cells into the lamellar epithelium was observed as of 6 h post clipping. We conclude that the differential response to clipping supports that this is a painful procedure that evokes a transient specific physiological status.►Nerve bundles are present in the tail of teleosts suggesting a possibility of nociception. ►Classical stress parameters don't allow discrimination between clipped and handled groups. ►Fin clipping induces changes in behavior regarding spatial preference. ►Fin clipping induces an adrenergic response characterized by branchial mucus release.
Consumer awareness and the interest of retailers for the welfare of farmed animals, including fis... more Consumer awareness and the interest of retailers for the welfare of farmed animals, including fish, is increasing. Consequently, more research is carried out to further our knowledge on fish welfare in aquaculture, including transport and (pre)slaughter methods. Scientific evidence for nociception in fish as in other vertebrates is accruing. Similarities in anatomy and functioning of the nervous system among all vertebrates are demonstrated. It has also been shown that fish possess an explicit memory, and thus the necessary modalities for pain perception and awareness are present in fish. Our ultrastructural analysis has demonstrated the presence of A-δ and C-fibres in tailfin clips of common carp (Cyprinus carpio), fibres known to transmit nociceptive signals in vertebrates. In a first experiment, we defined a series of physiological (branchial mucus release and content and chloride cell migration) and behavioural parameters (light/dark preference, swimming activity). These paramet...
V-focus + oktober 2011 30 V-focus + oktober 2011 31 C o n t a c t dr. Wout Abbink T 0317-481181 E... more V-focus + oktober 2011 30 V-focus + oktober 2011 31 C o n t a c t dr. Wout Abbink T 0317-481181 E [email protected] Dit onderzoek is uitgevoerd binnen het beleidsondersteunend onderzoek in kader van EL&I-programma KB-12-002.03.003 Dierenwelzijn.
Chronic exposure to nitrogenous waste compounds by Jonathan Roques
Het effect van verhoogde ammonia concentratie in het water op fysiologie, groei en voeropname van... more Het effect van verhoogde ammonia concentratie in het water op fysiologie, groei en voeropname van Afrikaanse meerval (Clarias gariepinus)
The ammonia (NH3) and nitrate (NO3−) threshold concentrations in rearing water of juvenile pikepe... more The ammonia (NH3) and nitrate (NO3−) threshold concentrations in rearing water of juvenile pikeperch (Sander lucioperca) were assessed. Pikeperch with an initial mean (SD) weight of 17.7 (4.2) g were exposed to 0.9 (control), 3.6, 5.2, 7.1, 11.2 and 18.9 μM NH3 in the water for 42 days. Plasma NH4+ concentrations stayed at control levels (~650 μM) up to 11.2 μMNH3 in the water. At the highestwater NH3 concentration tested, plasma
NH4+ had more than doubled to 1400 μM. Based on the specific growth rate, the EC10 value for NH3 was 5.7 μM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO3− for 42 days, mean (SD) plasma NO3− concentrations increased linearly from 88 (47) to 5993 (899) μM at the highest ambient NO3− level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO3− exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3.4 μM(0.05 mg NH3–N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3− we advise not to exceed 25 mM (350 mg NO3– - N/L). This criterion is based on the highest NO3− concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO3− threshold probably exceeds 25.6 mM.
The nitrite threshold concentration in rearing water of African catfish (Clarias gariepinus) was ... more The nitrite threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. African catfish with an initial mean (SD) weight of 219.7 (57.8) g were exposed to an
increasing range of water nitrite from 6 (Control) to 928 lM nitrite for 28 days. Mean (SD) plasma nitrite concentrations increased from 5.0 (3.6) to 32.5 (12.6) lM at 928 lM ambient nitrite. The
increase in nitrite was accompanied by gradual increase in plasma nitrate from 41.6 (28.4) lM to 420.2 (106.4) lM. Haematocrit, haemoglobin, methemoglobin, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not
affected. Feed intake, final weight, SGR, FCR and mortality were not affected. We advise not to exceed a water nitrite concentration of 43 lM (0.6 mg L-1 NO2 - -N) to prevent the risk of
reduced growth and feed intake in African catfish aquaculture.
The nitrate threshold concentration in rearing water of African catfish (Clarias gariepinus) was ... more The nitrate threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. Female African catfish with an initial mean (SD) weight of 154.3 (7.5) g were exposed to
0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) lM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9
(9.0) lM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake and specific growth rate were significantly
reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L
-1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
Aquaculture, 2010
The threshold concentration for NH3 in rearing water of African catfish (Clarias gariepinus) was ... more The threshold concentration for NH3 in rearing water of African catfish (Clarias gariepinus) was assessed. African catfish with an initial mean (SD) weight of 141.0 (24) g were exposed to five different Tamm [sum of NH3 and NH4+] concentrations: 0.37 (Control), 1.06, 2.12, 5.16 and 19.7 mM, which concurs with NH3 concentrations of 4 (Control), 14, 38, 176 and 1084 μM. Plasma concentrations of NH4+, cortisol, glucose and lactate, plasma osmolality, gill morphology, branchial Na+/K+-ATPase activity, feed intake and specific growth rate were monitored. No effect of water NH3 on plasma NH4+ concentrations was detected. Feed intake and specific growth rate were severely affected at exposure to water NH3 concentrations above 90 μM (calculated EC10 values: 89 and 122 μM). No major disturbances in physiological blood parameters were observed at these NH3 concentrations, but gill morphology (a remarkably sensitive stress indicator) deteriorated significantly. Based on the lower limit of the 95% confidence interval for EC10, we advise for African catfish not to exceed a water NH3 concentration of 24 μM (0.34 mg NH3-N/L). This finding is relevant for design and management of African catfish production systems.
Aquacultuur, Feb 28, 2014
Effect of road transportation by Jonathan Roques
Of the many stressors in aquaculture, transportation of fish has remained poorly studied. The obj... more Of the many stressors in aquaculture, transportation of fish has remained poorly studied. The objective of this study was therefore to assess the effects of a (simulated) commercial transportation on stress physiology of market-size African catfish (Clarias gariepinus). Catfish weighing approximately 1.25 kg were returned to the farm after 3 h of trucktransportation, and stress-related parameters were measured for up to 72 h following return. Recovery from transportation was assessed through blood samples measuring plasma cortisol, glucose and nonesterified
fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were
further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across
all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water
conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.
The objective of this study was to assess the effects of transportation of marketable eel (0.15 k... more The objective of this study was to assess the effects of transportation of marketable eel (0.15 kg) in the Netherlands with respect to welfare. Eels (Anguilla anguilla) were obtained from a commercial farm and acclimatized for 7 weeks at the laboratory.
Fish were transported according to regular commercial procedures. The animals were placed in water-filled transport tanks on the trailer. Fish density increased from 72 kg m
-3 (husbandry) to 206 kg m-3 (fasting) and was further increased to 270–290 kg m -3 during transport. Fish transport
lasted 3 h after which the eels were returned to laboratory recirculation systems to measure parameters indicative of stress load, i.e. mortality, plasma cortisol, lactate and non-esterified fatty
acids (NEFA) as well as gill morphology. Samples were taken at 0, 6, 24, 48 and 72 h after transport in transported fish and on-transported counterparts (controls). Transportation affected water quality within known tolerable limits. No mortality during or after transport was observed. After 6 h, plasma cortisol levels had returned to baseline. However, energy metabolism had increased suggesting that transportation of eels resulted in an increased energy demand that lasted for at least 72 h in the fasted animals. Thus, it is conceivable that exposure to adverse conditions, prior to stunning/killing, in a slaughterhouse may result in allostatic overload in eel.
Papers by Jonathan Roques
Finding optimal culture conditions for wolffish sp (Anarhichas sp.) in RAS 2015-16 University lec... more Finding optimal culture conditions for wolffish sp (Anarhichas sp.) in RAS 2015-16 University lecturer (ATER) -Équipe Écologie, Évolution, Symbiose, laboratoire Écologie et Biologie des Interactions, Université de Poitiers, France 'Stress response in terrestrial isopods' Defining and characterizing the stress response in terrestrial isopods. Comparative study and multidisciplinary approach; physiology and behavior 2014 Researcher (ATER)-Département de Biologie, Centre Universitaire de Mayotte, France 'Impact of waste water on physiology and osmoregulation of mangrove crabs' In vitro exposure of mangrove crabs to domestic effluent to validate an innovative waste water treatment solution in a densely populated island. Setting up of the biology laboratory 2009-13 Doctoral researcher,
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Finding optimal conditions for Yellowtail Kingfish by Jonathan Roques
22, 26 (experimental) and 30 g L-1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L-1 (7.61 +/- 0.19,
7.61 +/- 0.01 and 7.61 +/- 0.13% day-1, respectively)
had higher growth rates than fish at 26 and 30 g L-1 (7.10 +/- 0.05 and 6.97 +/- 0.06% day-1 respectively). The higher growth rate at
lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture
species.
combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21 °C to 26.5 °C resulted in a 54% increase in the fish's final weight after 30 days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish
could not adapt.
Nociception and pain in fish by Jonathan Roques
electrical stimuli, which do not stun immediately, are perceived by fish. We investigated responses of handheld Mozambique tilapia (Oreochromismossambicus) to a standardized electric shock applied to the tailfin. The handling with the resulting unavoidable acute stress response was carefully controlled for. Fish responses
were analyzed up to 24 h following the shock. Electric shock resulted in slightly higher levels in plasma cortisol, lactate, ionic levels, and osmolality, than handling alone. Plasma glucose had significantly increased 6 h after shock compared to handling, indicative of enhanced adrenergic activity. Mucus release from the gills, branchial Na+/K+ ATPase activity, and chloride cell migration and proliferation, parameters that will change with
strong adrenergic activation, were not affected. Decreased swimming activity and delay in resumption of chafing behavior indicated a stronger and differential response toward the electric shock. Responses to handling lasted shorter compared to those to an electric shock. The differential and stronger responses to the electric shock suggest that fish perceived the shock
potentially as painful.
Chronic exposure to nitrogenous waste compounds by Jonathan Roques
NH4+ had more than doubled to 1400 μM. Based on the specific growth rate, the EC10 value for NH3 was 5.7 μM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO3− for 42 days, mean (SD) plasma NO3− concentrations increased linearly from 88 (47) to 5993 (899) μM at the highest ambient NO3− level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO3− exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3.4 μM(0.05 mg NH3–N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3− we advise not to exceed 25 mM (350 mg NO3– - N/L). This criterion is based on the highest NO3− concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO3− threshold probably exceeds 25.6 mM.
increasing range of water nitrite from 6 (Control) to 928 lM nitrite for 28 days. Mean (SD) plasma nitrite concentrations increased from 5.0 (3.6) to 32.5 (12.6) lM at 928 lM ambient nitrite. The
increase in nitrite was accompanied by gradual increase in plasma nitrate from 41.6 (28.4) lM to 420.2 (106.4) lM. Haematocrit, haemoglobin, methemoglobin, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not
affected. Feed intake, final weight, SGR, FCR and mortality were not affected. We advise not to exceed a water nitrite concentration of 43 lM (0.6 mg L-1 NO2 - -N) to prevent the risk of
reduced growth and feed intake in African catfish aquaculture.
0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) lM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9
(9.0) lM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake and specific growth rate were significantly
reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L
-1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
Effect of road transportation by Jonathan Roques
fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were
further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across
all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water
conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.
Fish were transported according to regular commercial procedures. The animals were placed in water-filled transport tanks on the trailer. Fish density increased from 72 kg m
-3 (husbandry) to 206 kg m-3 (fasting) and was further increased to 270–290 kg m -3 during transport. Fish transport
lasted 3 h after which the eels were returned to laboratory recirculation systems to measure parameters indicative of stress load, i.e. mortality, plasma cortisol, lactate and non-esterified fatty
acids (NEFA) as well as gill morphology. Samples were taken at 0, 6, 24, 48 and 72 h after transport in transported fish and on-transported counterparts (controls). Transportation affected water quality within known tolerable limits. No mortality during or after transport was observed. After 6 h, plasma cortisol levels had returned to baseline. However, energy metabolism had increased suggesting that transportation of eels resulted in an increased energy demand that lasted for at least 72 h in the fasted animals. Thus, it is conceivable that exposure to adverse conditions, prior to stunning/killing, in a slaughterhouse may result in allostatic overload in eel.
Papers by Jonathan Roques
22, 26 (experimental) and 30 g L-1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L-1 (7.61 +/- 0.19,
7.61 +/- 0.01 and 7.61 +/- 0.13% day-1, respectively)
had higher growth rates than fish at 26 and 30 g L-1 (7.10 +/- 0.05 and 6.97 +/- 0.06% day-1 respectively). The higher growth rate at
lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture
species.
combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21 °C to 26.5 °C resulted in a 54% increase in the fish's final weight after 30 days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish
could not adapt.
electrical stimuli, which do not stun immediately, are perceived by fish. We investigated responses of handheld Mozambique tilapia (Oreochromismossambicus) to a standardized electric shock applied to the tailfin. The handling with the resulting unavoidable acute stress response was carefully controlled for. Fish responses
were analyzed up to 24 h following the shock. Electric shock resulted in slightly higher levels in plasma cortisol, lactate, ionic levels, and osmolality, than handling alone. Plasma glucose had significantly increased 6 h after shock compared to handling, indicative of enhanced adrenergic activity. Mucus release from the gills, branchial Na+/K+ ATPase activity, and chloride cell migration and proliferation, parameters that will change with
strong adrenergic activation, were not affected. Decreased swimming activity and delay in resumption of chafing behavior indicated a stronger and differential response toward the electric shock. Responses to handling lasted shorter compared to those to an electric shock. The differential and stronger responses to the electric shock suggest that fish perceived the shock
potentially as painful.
NH4+ had more than doubled to 1400 μM. Based on the specific growth rate, the EC10 value for NH3 was 5.7 μM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO3− for 42 days, mean (SD) plasma NO3− concentrations increased linearly from 88 (47) to 5993 (899) μM at the highest ambient NO3− level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO3− exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3.4 μM(0.05 mg NH3–N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3− we advise not to exceed 25 mM (350 mg NO3– - N/L). This criterion is based on the highest NO3− concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO3− threshold probably exceeds 25.6 mM.
increasing range of water nitrite from 6 (Control) to 928 lM nitrite for 28 days. Mean (SD) plasma nitrite concentrations increased from 5.0 (3.6) to 32.5 (12.6) lM at 928 lM ambient nitrite. The
increase in nitrite was accompanied by gradual increase in plasma nitrate from 41.6 (28.4) lM to 420.2 (106.4) lM. Haematocrit, haemoglobin, methemoglobin, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not
affected. Feed intake, final weight, SGR, FCR and mortality were not affected. We advise not to exceed a water nitrite concentration of 43 lM (0.6 mg L-1 NO2 - -N) to prevent the risk of
reduced growth and feed intake in African catfish aquaculture.
0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) lM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9
(9.0) lM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake and specific growth rate were significantly
reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L
-1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were
further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across
all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water
conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.
Fish were transported according to regular commercial procedures. The animals were placed in water-filled transport tanks on the trailer. Fish density increased from 72 kg m
-3 (husbandry) to 206 kg m-3 (fasting) and was further increased to 270–290 kg m -3 during transport. Fish transport
lasted 3 h after which the eels were returned to laboratory recirculation systems to measure parameters indicative of stress load, i.e. mortality, plasma cortisol, lactate and non-esterified fatty
acids (NEFA) as well as gill morphology. Samples were taken at 0, 6, 24, 48 and 72 h after transport in transported fish and on-transported counterparts (controls). Transportation affected water quality within known tolerable limits. No mortality during or after transport was observed. After 6 h, plasma cortisol levels had returned to baseline. However, energy metabolism had increased suggesting that transportation of eels resulted in an increased energy demand that lasted for at least 72 h in the fasted animals. Thus, it is conceivable that exposure to adverse conditions, prior to stunning/killing, in a slaughterhouse may result in allostatic overload in eel.
Part 1: acute discomfort: Pain in fish
The question of the capability of fish to feel pain is a hot topic. In this first part of my PhD thesis, I examined the effects of standardized, potentially painful stimuli (tailfin clip and electric shocks) in several fish species, namely Nile and Mozambique tilapia’s (Oreochromis niloticus and Oreochromis mossambicus), Common carp, Cyprinus carpio and zebrafish, Danio rerio. I investigated a wide array of physiological and behavioral parameters to help answering the debated question, ‘do fish feel pain?’. The next question should be ‘to which extent?’.
Part 2: chronic discomfort: effect of nitrogenous waste on growth performance in RAS
Nitrogenous-waste compounds (ammonia, nitrite and nitrate) are limiting factors in recirculating aquaculture systems. In the second part of my thesis, I determined the threshold levels of these compounds that African catfish (Clarias gariepinus) and pikeperch (Sander lucioperca) could tolerate. These two species are important species for the Dutch aquaculture sector. I followed both growth and physiological parameters after a month-long exposure.
PhD thesis, Radboud University Nijmegen, 2013.
Supervisors: Prof. Dr. Gert Flik – Dr. Hans van de Vis – Dr. Wout Abbink