Mucosal and systemic physiological changes underscore the welfare risks of environmental hydrogen sulphide in post-smolt Atlantic salmon (Salmo salar)

publishedVersio

Health and welfare of Atlantic salmon in FishGLOBE V5 -a novel closed containment system at sea

Closed-containment (CCS) systems offer several advantages in controlling the production environment for Atlantic salmon (Salmo salar) aquaculture, especially at sea, where fish are more exposed to challenging environmental conditions. Here, we report the health and welfare of Atlantic salmon in FishGLOBE V5, a 3500 m3 semi-closed containment system. A group of 200,000 post-smolts was followed from a recirculating aquaculture system (RAS) facility, then for three and a half months in FishGLOBE V5, and three months after release in net pens. Fish samples were collected at four time points during the production period, while water quality was evaluated when the fish were in FishGLOBE V5. The water quality in FishGLOBE V5 was within the recommended range for salmon post-smolts. The mortality rate was 1.4% in FishGLOBE V5 and 4.9% in net pens. There was an increase in the prevalence of eye, snout and dorsal fin damages before the fish left the FishGLOBE V5 phase. The plasma level of magnesium was slightly elevated during this phase as well, indicating osmotic imbalance and stress. Histological evaluation of skin and gills showed sporadic cases of non-specific pathologies. In particular, the transitory stay in FishGLOBE V5 partially improved skin health, but not gill health. Gene expression profiling of some biomarkers showed that rearing fish in FishGLOBE V5 could influence the expression of genes involved in stress response, mucus production, and epithelial integrity. This study documented that rearing salmon for a certain period in FishGLOBE V5 during production affected different health and welfare indicators. These changes should be taken into consideration for the improvement of FishGLOBE V5 as a viable technology for post-smolt production at sea.Health and welfare of Atlantic salmon in FishGLOBE V5 -a novel closed containment system at seapublishedVersio

The optimum velocity for Atlantic salmon post-smolts in RAS is a compromise between muscle growth and fish welfare

It is increasingly common to rear Atlantic salmon smolts for longer periods in recirculating aquaculture systems (RAS) before transfer to sea cages. The conditions for this part of the life cycle are currently being optimized, especially the water velocity in the tanks since its impact has been correlated with. growth. Earlier studies indicate that higher water velocities promote growth in salmon, nonetheless, the optimal velocity and its associated health and welfare consequences are yet to be established. In the present study, we determined the effects of different water velocities on growth, muscle development and welfare to estimate the optimum velocity for the rearing of post-smolts in RAS. We divided 2400 salmon post-smolts (average start weight 80 g) into twelve tanks (200 fish per tank) and set the water velocities in four triplicate tanks to low (L) – 0.5 body length per second (BL/s); medium (M) – 1.0 BL/s; high (H) – 1.8 BL/s; and very high (VH) – 2.5 (BL/s). The velocity for the VH group was the highest tested for salmon post-smolts to date. The trial lasted for three months and organ samples were collected at three time points. Time-lapse cameras revealed a relatively even fish distribution in the tank in L and M groups. In contrast, fish in H and VH groups displayed strong schooling behavior at specific regions in the tanks. We observed a close to a linear relationship between water velocity and average growth rate, which resulted in a 5.7% higher average body weight in the VH group in comparison to the L group at termination. The condition factors of fish from the L group was lower than in the other three groups. Muscle cellularity analysis revealed smaller fibers in the L group, while bigger muscle fibers were identified in H and VH groups which contributed to somatic growth. Nonetheless, increased cases of inflammation were observed in H and VH groups. Muscle proteomics revealed decreased translation and carbohydrate activity in the L group. The overall external welfare status of the fish was favorable; however, increased incidence of skin damage (i.e., scale loss, hemorrhaging) and pelvic fin damage (i.e., splitting) in the H and VH groups was documented. Skin histology revealed relatively thinner epidermis at higher velocities. On the other hand, increased cases of aneurysm, lamellar clubbing and fusion were identified at higher velocities too. In conclusion, the increased body weight of fish reared in high water velocities was likely mostly due to enhanced somatic growth of muscle fibers. These findings provide further evidence that elevated water velocities have positive effects on the growth rate of post-smolts even at the highest levels tested to date. On the other hand, the external welfare scores, histological analyses and the molecular data indicate that mucosal health was negatively affected by higher velocities. Thus, based on this study, the optimal water velocity for long term rearing of salmon post-smolts in RAS is most likely located slightly above 1 body length per second.The optimum velocity for Atlantic salmon post-smolts in RAS is a compromise between muscle growth and fish welfarepublishedVersio

Consequences of continuous ozonation on the health and welfare of Atlantic salmon post-smolts in brackish water recirculating aquaculture system

This study investigated the biological consequences of 45-day continuous ozonation on Atlantic salmon (Salmo salar) post-smolts in a brackish water recirculating aquaculture system (RAS). There was no significant difference in survival, operational welfare indicators, and average weight at termination between the ozone-treated and control groups. Plasma biochemical analyses revealed that the creatinine level was significantly higher in the ozone-treated group than in the control at termination. Histological evaluation of skin health showed no significant difference between the two groups. On the other hand, quantitative histopathology disclosed that the ozone group exhibited a better gill health status than did the control group, particularly at the end of the trial. Mucosal transcriptomics revealed a distinct response profile between the gills and skin. At day 45, there were no differentially expressed genes (DEG) identified in the skin, in contrast to 242 ozone-induced DEGs in the gills. Assessment of the transcriptomic profiles over time revealed that temporal effects were of greater impact in skin compared to gills, regardless of the treatment. The treatment did not result in metabolomic dysregulation and the overall profile lent support to the transcriptomics data that temporal effects had a greater influence on the changes observed. Exposure to handling-confinement stress revealed that ozone treatment did not alter the ability of post-smolts to respond to a secondary stressor. In summary, the suite of health and welfare indicators collectively indicated that continuous ozonation resulted in minimal physiological perturbations in salmon post-smolts. The results are expected to contribute to optimising the rearing conditions for post-smolts in RAS.publishedVersio

The optimum velocity for Atlantic salmon post-smolts in RAS is a compromise between muscle growth and fish welfare

It is increasingly common to rear Atlantic salmon smolts for longer periods in recirculating aquaculture systems (RAS) before transfer to sea cages. The conditions for this part of the life cycle are currently being optimized, especially the water velocity in the tanks since its impact has been correlated with. growth. Earlier studies indicate that higher water velocities promote growth in salmon, nonetheless, the optimal velocity and its associated health and welfare consequences are yet to be established. In the present study, we determined the effects of different water velocities on growth, muscle development and welfare to estimate the optimum velocity for the rearing of post-smolts in RAS. We divided 2400 salmon post-smolts (average start weight 80 g) into twelve tanks (200 fish per tank) and set the water velocities in four triplicate tanks to low (L) – 0.5 body length per second (BL/s); medium (M) – 1.0 BL/s; high (H) – 1.8 BL/s; and very high (VH) – 2.5 (BL/s). The velocity for the VH group was the highest tested for salmon post-smolts to date. The trial lasted for three months and organ samples were collected at three time points. Time-lapse cameras revealed a relatively even fish distribution in the tank in L and M groups. In contrast, fish in H and VH groups displayed strong schooling behavior at specific regions in the tanks. We observed a close to a linear relationship between water velocity and average growth rate, which resulted in a 5.7% higher average body weight in the VH group in comparison to the L group at termination. The condition factors of fish from the L group was lower than in the other three groups. Muscle cellularity analysis revealed smaller fibers in the L group, while bigger muscle fibers were identified in H and VH groups which contributed to somatic growth. Nonetheless, increased cases of inflammation were observed in H and VH groups. Muscle proteomics revealed decreased translation and carbohydrate activity in the L group. The overall external welfare status of the fish was favorable; however, increased incidence of skin damage (i.e., scale loss, hemorrhaging) and pelvic fin damage (i.e., splitting) in the H and VH groups was documented. Skin histology revealed relatively thinner epidermis at higher velocities. On the other hand, increased cases of aneurysm, lamellar clubbing and fusion were identified at higher velocities too. In conclusion, the increased body weight of fish reared in high water velocities was likely mostly due to enhanced somatic growth of muscle fibers. These findings provide further evidence that elevated water velocities have positive effects on the growth rate of post-smolts even at the highest levels tested to date. On the other hand, the external welfare scores, histological analyses and the molecular data indicate that mucosal health was negatively affected by higher velocities. Thus, based on this study, the optimal water velocity for long term rearing of salmon post-smolts in RAS is most likely located slightly above 1 body length per second

Intermittent administration of peracetic acid is a mild environmental stressor that elicits mucosal and systemic adaptive responses from Atlantic salmon post-smolts

Background Fish encounter oxidative stress several times during their lifetime, and it has a pervasive influence on their health and welfare. One of the triggers of oxidative stress in fish farming is the use of oxidative disinfectants to improve rearing conditions, especially in production systems employing recirculation technology. Here we report the physiological and morphological adaptive responses of Atlantic salmon (Salmo salar L.) post-smolts to intermittent exposure to a potent oxidative agent peracetic acid (PAA). Fish reared in semi-commercial scale brackish water recirculating aquaculture system (RAS) were exposed to 1 ppm PAA every 3 days over 6 weeks. Mucosal and systemic responses were profiled before exposure, 22 and 45 days during the intermittent PAA administration. Results Oxidative stress was likely triggered as plasma antioxidant capacity increased significantly during the exposure period. Adaptive stress response to the periodic oxidant challenge was likewise demonstrated in the changes in plasma glucose and lactate levels. PAA-induced alterations in the transcription of antioxidants, cytokines, heat shock proteins and mucin genes showed a tissue-specific pattern: downregulation was observed in the gills and olfactory rosette, upregulation occurred in the skin, and no substantial changes in the liver. Further, PAA exposure resulted in histological changes in key mucosal organs (i.e. olfactory rosette, skin and gills); pathological alterations were predominant in the gills where cases of epithelial lifting, hypertrophy and clubbing were prevalent. In addition, intermittent PAA administration resulted in an apparent overproduction of mucus in the nasal mucosa. Lastly, PAA did not dramatically alter the ability of salmon to mount a physiological stress response in the presence of a secondary stressor, though some subtle interference was documented in the kinetics and magnitude of plasma cortisol and glucose response post-stress. Conclusions The present study collectively demonstrated that intermittent oxidant exposure was a mild environmental stressor that salmon could mount strong adaptive responses at systemic and mucosal levels. The results will be valuable in optimising the rearing conditions of post-smolts in RAS, especially in adopting water treatment strategies that do not considerably interfere with fish health and welfare

Intermittent administration of peracetic acid is a mild environmental stressor that elicits mucosal and systemic adaptive responses from Atlantic salmon post-smolts

Background Fish encounter oxidative stress several times during their lifetime, and it has a pervasive influence on their health and welfare. One of the triggers of oxidative stress in fish farming is the use of oxidative disinfectants to improve rearing conditions, especially in production systems employing recirculation technology. Here we report the physiological and morphological adaptive responses of Atlantic salmon (Salmo salar L.) post-smolts to intermittent exposure to a potent oxidative agent peracetic acid (PAA). Fish reared in semi-commercial scale brackish water recirculating aquaculture system (RAS) were exposed to 1 ppm PAA every 3 days over 6 weeks. Mucosal and systemic responses were profiled before exposure, 22 and 45 days during the intermittent PAA administration. Results Oxidative stress was likely triggered as plasma antioxidant capacity increased significantly during the exposure period. Adaptive stress response to the periodic oxidant challenge was likewise demonstrated in the changes in plasma glucose and lactate levels. PAA-induced alterations in the transcription of antioxidants, cytokines, heat shock proteins and mucin genes showed a tissue-specific pattern: downregulation was observed in the gills and olfactory rosette, upregulation occurred in the skin, and no substantial changes in the liver. Further, PAA exposure resulted in histological changes in key mucosal organs (i.e. olfactory rosette, skin and gills); pathological alterations were predominant in the gills where cases of epithelial lifting, hypertrophy and clubbing were prevalent. In addition, intermittent PAA administration resulted in an apparent overproduction of mucus in the nasal mucosa. Lastly, PAA did not dramatically alter the ability of salmon to mount a physiological stress response in the presence of a secondary stressor, though some subtle interference was documented in the kinetics and magnitude of plasma cortisol and glucose response post-stress. Conclusions The present study collectively demonstrated that intermittent oxidant exposure was a mild environmental stressor that salmon could mount strong adaptive responses at systemic and mucosal levels. The results will be valuable in optimising the rearing conditions of post-smolts in RAS, especially in adopting water treatment strategies that do not considerably interfere with fish health and welfare.Intermittent administration of peracetic acid is a mild environmental stressor that elicits mucosal and systemic adaptive responses from Atlantic salmon post-smoltspublishedVersio

FishGLOBE – a new S-CCS concept for farming salmon

Denne rapporten beskriver vannkvalitet og ytelse og velferd hos post-smolt som har gått i det semilukkede anlegget FishGLOBE. I tillegg har FishGLOBE V3 og V5 blitt modellert med CFD modellering. Fire ulike caser ble modellert i V5. Modelleringen viste at det originale designet uten vannavdelere ga best vannhastighet og fordeling. En fiskegruppe på 200 000 post-smolt ble fulgt fra RAS anlegg, så fire måneder i FishGLOBE, og tre måneder etter sjøutsett i åpen not. Vannkvalitetsvariable ble målt rett etter innsett i globen, mens biologiske målinger av fisk ble utført ved alle fire tidspunktene. Vannkvaliteten i FishGLOBE var innenfor det anbefalte. Dødeligheten var 1,4 % i globen og 4,9 % i sjøfasen. Veksten i FishGLOBE viste TGC på 4,0 og SGR på 1,3. Fisken hadde litt forhøyede nivåer av Mg i FishGLOBE, noe som kan bety at den var i osmotisk ubalanse og stresset. Det var økt ekspresjon av hsp90 og Mucin hos fisk i globen, noe som kan tyde på stress. Mucin-nivået kan også øke når skinnet styrkes. Histologisnitt av skinn og gjelle viste en bedring hos fisken i globen. Bedring i gjellestatus kan forklares med god vannkvalitet, lav turbiditet og TSS. Det ble registrert en stor andel av øyeskader hos fisken i FishGLOBE. Det er ukjent hva dette skyldes.Two-hundred-thousand post-smolts were followed from RAS, to four months in FishGLOBE, and three months after transfer to sea cage. Water quality in FishGLOBE was as recommended. Mortality in the globe was 1.4 % and 4.9 % in sea cage. The growth; TGC = 4.0 and SGR = 1.3. The fish had slightly elevated levels of Mg in FishGLOBE and increased expression of hsp90 and mucin. Histology showed that skin and gills status improved in the globe. A large proportion of eye injuries were registered in FishGLOBE. It is unknown what caused this.publishedVersionpublishedVersio

Nytt S-CCS konsept for oppdrett av laks - Postsmoltproduksjon i FishGLOBE

Denne rapporten beskriver vannkvalitet og ytelse og velferd hos post-smolt som har gått i det semilukkede anlegget FishGLOBE. I tillegg har FishGLOBE V3 og V5 blitt modellert med CFD modellering. Fire ulike caser ble modellert i V5. Modelleringen viste at det originale designet uten vannavdelere ga best vannhastighet og fordeling. En fiskegruppe på 200 000 post-smolt ble fulgt fra RAS anlegg, så fire måneder i FishGLOBE, og tre måneder etter sjøutsett i åpen not. Vannkvalitetsvariable ble målt rett etter innsett i globen, mens biologiske målinger av fisk ble utført ved alle fire tidspunktene. Vannkvaliteten i FishGLOBE var innenfor det anbefalte. Dødeligheten var 1,4 % i globen og 4,9 % i sjøfasen. Veksten i FishGLOBE viste TGC på 4,0 og SGR på 1,3. Fisken hadde litt forhøyede nivåer av Mg i FishGLOBE, noe som kan bety at den var i osmotisk ubalanse og stresset. Det var økt ekspresjon av hsp90 og Mucin hos fisk i globen, noe som kan tyde på stress. Mucin-nivået kan også øke når skinnet styrkes. Histologisnitt av skinn og gjelle viste en bedring hos fisken i globen. Bedring i gjellestatus kan forklares med god vannkvalitet, lav turbiditet og TSS. Det ble registrert en stor andel av øyeskader hos fisken i FishGLOBE. Det er ukjent hva dette skyldes

Health and welfare of Atlantic salmon in FishGLOBE V5 -a novel closed containment system at sea

Closed-containment (CCS) systems offer several advantages in controlling the production environment for Atlantic salmon (Salmo salar) aquaculture, especially at sea, where fish are more exposed to challenging environmental conditions. Here, we report the health and welfare of Atlantic salmon in FishGLOBE V5, a 3500 m3 semi-closed containment system. A group of 200,000 post-smolts was followed from a recirculating aquaculture system (RAS) facility, then for three and a half months in FishGLOBE V5, and three months after release in net pens. Fish samples were collected at four time points during the production period, while water quality was evaluated when the fish were in FishGLOBE V5. The water quality in FishGLOBE V5 was within the recommended range for salmon post-smolts. The mortality rate was 1.4% in FishGLOBE V5 and 4.9% in net pens. There was an increase in the prevalence of eye, snout and dorsal fin damages before the fish left the FishGLOBE V5 phase. The plasma level of magnesium was slightly elevated during this phase as well, indicating osmotic imbalance and stress. Histological evaluation of skin and gills showed sporadic cases of non-specific pathologies. In particular, the transitory stay in FishGLOBE V5 partially improved skin health, but not gill health. Gene expression profiling of some biomarkers showed that rearing fish in FishGLOBE V5 could influence the expression of genes involved in stress response, mucus production, and epithelial integrity. This study documented that rearing salmon for a certain period in FishGLOBE V5 during production affected different health and welfare indicators. These changes should be taken into consideration for the improvement of FishGLOBE V5 as a viable technology for post-smolt production at sea