Welfare Of Atlantic Salmon Research Articles

Evaluation of stress in farmed Atlantic salmon (Salmo salar) using different biological matrices

Atlantic salmon were subjected to an acute crowding scenario, and their subsequent stress responses were observed under three distinct swimming speed/water flow (WF) conditions: 0.5, 1, and 1.5 body lengths per second (BL/s). Feces, dermal mucus, and plasma were collected for analysis at 1, 6, and 24 h (h) post-stress. Additionally, the head kidney and two regions of the brain (pituitary and POA) were collected for transcript expression analysis. Fish swimming at 0.5 BL/s exhibited higher pre-stress (baseline) cortisol levels. Across all groups and matrices, the highest cortisol/cortisol metabolites (CM) levels were observed at the 1 h post-stress sampling point. At 6 h (second sampling time point), a clear decline toward baseline levels were observe in all groups. Significant increases in mean plasma glucose levels were observed at 1 h post-stress for all groups. The mean plasma lactate levels varied based on WF treatments, with a significant increase observed at 1 h only for the 1.5 BL/s group. Additionally, significant decreases in mean plasma lactate were noted at 6 and 24 h post-stress for some groups. The mRNA abundances of the tested genes (star, cyp17a1, hsd11β2, srd5a1) increased following the stress events. These changes were not uniform across all groups and were tissue dependent. In summary, the results indicate that mucus and feces can be used as potentially less invasive matrices than blood for evaluating stress and, consequently, the welfare of Atlantic salmon in captivity.

Norway spruce extracts (NSEs) as bioactive compounds in novel feeds: Effect on intestinal immune-related biomarkers, morphometry and microbiota in Atlantic salmon pre-smolts

Compounds from woody biomass are promising candidates as feed additives to improve fish health and welfare of Atlantic salmon (Salmo salar) during the productive cycleng. Thus, conidendrin- and isorhapontin-based extracts (NSEs) from Norway spruce (Picea abies) were evaluated at different levels in a four-week trial. A commercial-like diet (D1) was supplemented with 0.2% of a commercial β-glucan (D2) or with NSEs at 0.02%, 0.1% and 0.2% (D3-D8). No significant differences were found in growth, intestinal morphometry and microbiota at the genus level. Immune-related biomarkers in distal intestine from D5 and D6 indicated an activation of a pro-inflammatory response by the up-regulation of il1b, as in D2. Interestingly, isorhapontin-based extract at higher inclusion level (D8), showed a down-regulation of both pro- and anti-inflammatory- genes, suggesting maintenance of homeostasis. These results showed the importance of source and inclusion levels of bioactive compounds on the regulatory balance associated with fish immune response.

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.

Impact of dietary zinc and seawater transfer on zinc status, availability, endogenous loss and osmoregulatory responses in Atlantic salmon smolt fed low fish meal feeds

Atlantic salmon fed low fish meal feeds supplemented with zinc (Zn) were studied in two feeding trials. In trial I, Atlantic salmon parr were fed six graded Zn levels (40 to 249 mg kg−1 as ZnSO4) for 8 weeks in freshwater followed by a 4-week seawater phase. In trial II, Atlantic salmon post-smolt were fed for 10 weeks in SW with 10 dietary Zn levels (45 to 280 mg kg−1), either as ZnSO4 or Zn-glycinate. Growth was unaffected by dietary Zn in both trials. Dietary Zn affected concentration of Na + and K+ ions in plasma, branchial and intestinal expression of sodium potassium ATPase, tissue and body Zn status, and cataracts. Seawater transfer significantly reduced apparent availability, body and tissue levels of Zn due to increased endogenous Zn loss. Atlantic salmon post-smolt in seawater improved body and tissue Zn status with increasing dietary Zn levels, irrespective of the Zn source. Body or tissue saturation of Zn occurred at dietary Zn levels between 137 and 156 mg kg−1 with smolts in freshwater and 181 to 218 mg kg−1 in SW post-smolts. Dietary Zn levels below 180 mg kg−1 in low fish meal feeds compromised the Zn status and welfare of Atlantic salmon in seawater.

Evaluating the Effects of a Short‐Term Feed Restriction Period on the Behavior and Welfare of Atlantic Salmon, Salmo salar, parr Using Social Network Analysis and Fin Damage

AbstractSocial network analysis (SNA) was used to quantify the role of behavioral interactions on the frequency and severity of fin damage in Atlantic salmon, Salmo salar, parr subjected to a short feed restriction period of 10 d. Dorsal fin erosion was observed in both feed‐restricted (FR) and control (C) groups of fish, but was significantly more frequent and severe in FR groups. FR fish had a significantly lower weight, length, and poorer body condition in comparison to C groups. Social networks based on aggressive interactions showed significantly higher overall degree‐centrality, clustering coefficients, out and in‐degree centralities in FR groups. This led to the formation of clusters of fish into initiators and receivers of aggression. Only the receivers of aggression exhibited dorsal fin damage, while initiators did not. Initiators and receivers of aggression in FR groups retained their roles even after control conditions were restored, suggesting that short periods of feed restriction can lead to permanent modifications in aggressive behavior. This study demonstrates the applied value of using SNA to investigate the longer term effects that aggressive behavioral interactions have on fin damage and welfare in Atlantic salmon.