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

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.

Exsanguination of turbot and the effect on fillet quality measured mechanically, by sensory evaluation, and with computer vision.

In order to investigate the impact of blood residues on the end quality of exsanguinated and unbled farmed turbot (Scophthalmus maximus), meat quality was evaluated using mechanical, sensory, and computer imaging techniques. The results show that exsanguination is important for improving the visual appearance, and the blood residue could be quantified using a computer imaging system. After 6 d of storage, mechanical analysis using puncture test or shear force showed no difference between exsanguinated and unbled fish. The trained taste panel was unable to detect any differences between exsanguinated and unbled fish after 6 and 14 d of storage. We conclude that over a 2-wk period the blood residue in turbot meat does not affect texture or sensory quality, but does affect the visual appearance.