Live chilling of Atlantic salmon: physiological response to handling and temperature decrease on welfare

Abstract

Investigation of the physiological effects of live chilling in Atlantic salmon, Salmo salar, has been performed in two experiments. In the first, fish (mean weight 840 g) acclimatized to either 16, 8, or 4°C were directly transferred horizontally or vertically (9 combinations) to water temperatures of 16, 8, 4, or 0°C using a dip net. Blood samples were collected at 1 and 6 h (h) post-transfer. In the second experiment, fish (mean weight 916 g) acclimatized to 16°C were exposed to four temperature-drop regimes (no physical handling): 16-4°C (over 5 h), 16-4°C (over 1 h), 16-0°C (over 5 h), and 16-0°C (over 1 h). Blood samples were collected 1 h post-temperature drop. Physical transfers in the first trial, i.e., temperature drops, resulted in immediate (1 h) increases in blood lactate concentrations at all three temperatures, but levels were significantly reduced and close to pre-transfer levels after 6 h. Horizontal transfers, i.e., 16-16°C, 8-8°C, and 4-4°C, resulted in similar increases and were not significantly different from the groups exposed to temperature drops. The most severe vertical transfer (16-0) resulted in a swift loss of equilibrium and eventually death. In experiment 2, temperature drops from 16 to 4°C and from 16 to 0°C over a period of one or 5 h, without physically handling the fish, resulted in no significant increases in any of the measured parameters 1 h post-transfer, except in the 16-0 (1 h) group. The latter experienced a significant increase in blood sodium, glucose, lactate, and cortisol levels compared to all other groups. The results suggest that salmon are capable of tolerating relatively steep temperature drops without any significant negative effects on blood stress parameters and that physical stress from handling overrides the effect of thermal insults.

Stability of frozen fillets from silver catfish anesthetized with essential oil ofLippia albaprior to electrical stunning or hypothermia

“…Both dissolved oxygen and pH were however, within the requirements for silver catfish (Baldisserotto & Silva, ). Despite being resistant to low temperature (Barcellos, Woehl, Wassermann, Quevedo, Ittzes, & Krieger, ), silver catfish can be stressed by the low temperature used in the hypothermia tank as Atlantic salmon, which are also resistant to low temperature, did show pain and suffering when submitted to temperature drop from 16 to 0°C within 1 h (Foss, Grimsbo, Vikingstad, Nortvedt, Slinde, & Roth, ). Nile tilapia also showed increased levels of chemical indicators of stress after hypothermia stunning (Oliveira Filho, Girao, Melo, & Viegas, ).…”

Pre-mortem stress and the subsequent effect on flesh quality of pre-rigor filleted Atlantic salmon (Salmo salar L.) during ice storage

“…Which factors are most relevant as stressors, pumping, live chilling or CO 2 ? With live chilling, Foss et al (2012) showed that, in a controlled environment, a temperature drop from 4 and 8 to 0°C has no significant stress effect. The observed stress effects in the presented study can only be explained by crowding, pumping and CO 2 alone.…”

Stress response of Salmo salar (Linnaeus 1758) facing low abundance infestation of Caligus rogercresseyi (Boxshall & Bravo 2000), an object in the tank, and handling

“…Increases in plasma lactate have been previously described for S. salar after physical handling (Foss et al . ), and in S. trutta infested with L. salmonis, where fish showed flashing behaviour (Wells et al . ).…”