Carotenoid and lipid content in muscle of Atlantic salmon, Salmo salar, transferred to seawater as 0+ or 1+ smolts.

Accumulation of lipids and carotenoids, including 4'-hydroxyechinenone (4'-hydroxy-beta,beta-carotene-4-one), growth and condition factor were investigated in Atlantic salmon (Salmo salar) transferred to seawater as 0+ and 1+ smolts. Salmon were fed a diet with 30 mg/kg astaxanthin (3,3'-dihydroxy-beta,beta-carotene-4,4'-dione) and 30 mg/kg canthaxanthin (beta,beta-carotene-4,4'-dione) for 35 weeks. The 0+ smolt contained more carotenoids than the 1+ smolt when mass differences were corrected for (P<0.0001), a difference also reflected by the tristimulus colour measurements (C1E a*- and b*-values). Astaxanthin and canthaxanthin comprised more than 93% of the total carotenoids, but small differences were observed in carotenoid composition. The condition factor was significantly higher in 0+ than 1+ smolts after correction for mass differences (P<0.01). There was a high correlation between ln-transformed muscle lipid (%) and ln-transformed body mass for 0+(R2=0.94) and 1+smolts (R2=0.97). The canthaxanthin metabolite 4'-hydroxyechinenone was isolated from muscle of Atlantic salmon fed a diet supplemented with canthaxanthin. It was characterised and identified by its absorption maximum (lambda(max)=458 nm in n-hexane), mass spectrometry (M+=566) and co-chromatography with authentic standard obtained by NaBH4-reduction of canthaxanthin on thin-layer chromatography and HPLC. HPLC of the camphanates of 4'-hydroxyechinenone revealed a stereoselective transformation in favour of the (4'S)-isomer, the (4'S) and (4'R)-isomers comprising approximately 81 and 19% of the total 4'-hydroxyechinenone, respectively. The percentage of 4'-hydroxyechineone of total carotenoids ranged from 1.3 to 3.1% and declined with fish size (P<0.001). We conclude that effects of time of seawater transfer of Atlantic salmon smolts have significant effect on carotenoid accumulation and other quality traits. The detailed biochemical and physiological basis for these differences require further elucidation.

Protocol for assessing brain function in fish and the effectiveness of methods used to stun and kill them.

A method for the evaluation of brain function in fish has been developed which is based on assessments of self-initiated behaviours, responses to stimulation, and reflexes. These assessments were validated in several freshwater and marine species and applied to evaluate the brain function of fish while they were anaesthetised and while they were being killed by a variety of methods. The results of these investigations were compared with published neurophysiological observations and it is concluded that some of the tests can be used to identify, with reasonable confidence, the state of awareness, and thus the capacity to experience suffering of several species of fish.

Commercial slaughter methods used on Atlantic salmon: determination of the onset of brain failure by electroencephalography.

This study investigated the effect of exsanguination without prior stunning, or carbon dioxide narcosis followed by exsanguination, or percussive stunning or spiking the brain, on the time taken to abolish the visual evoked responses (VERS) of farmed Atlantic salmon. Only percussive stunning and spiking killed the fish immediately and the other two methods resulted in aversive reactions by the fish. The VERS were lost between 148 and 440 seconds after exsanguination without stunning, and between 300 and 554 seconds after carbon dioxide narcosis followed by exsanguination. During both these procedures the fish showed strong aversive behaviour. In contrast, percussive stunning and spiking the brain could result in the immediate loss of VERS and no aversive reactions from the fish if the stun was applied correctly.