Ole Torrissen

Pigmentation of salmonids: effect of carotenoids in eggs and start-feeding diet on survival and growth rate

No effects of carotenoid levels were observed on the survival of eggs and alevins of Atlantic salmon (Salmo salar) in darkness. Light sensitivity increased with increasing amounts of carotenoids in the eggs. Diets supplemented with synthetic astaxanthin and cantaxanthin promoted growth rate during the early start-feeding period.

Pigmentation of salmonids: Interactions of astaxanthin and canthaxanthin on pigment deposition in rainbow trout

Abstract Rainbow trout ( Salmo gairdneri ) were fed six diets each containing a sum of astaxanthin and canthaxanthin of about 200 mg/kg for a total of 57 days. The relation between astaxanthin and canthaxanthin in the diets ranged from 100% to 0% of the sum, with intervals of 20%. The total concentrations of astaxanthin and canthaxanthin were determined in the flesh at the start of the experiment, after 36 days, and at the end of the experiment. The relative amounts of astaxanthin and canthaxanthin were measured in flesh, plasma and four sections of the digestive tract. Deposition of carotenoids in the flesh is described in relation to feeding time, individual fish weight and individual growth. The average astaxanthin and canthaxanthin concentration in the flesh increased from 0.05 mg/kg to 2.1 mg/kg after 57 days of feeding. Fish with individual body weight below 90 g deposited relatively low amounts of carotenoids compared to fish heavier than 90 g. The carotenoid concentration i in the flesh increased with increasing growth but leveled off for fish with a large absolute growth. The experiment shows that astaxanthin is deposited in the flesh more efficiently than canthaxanthin and that this is due to both preferred absorption in the digestive tract and deposition in the flesh. A combination of astaxanthin and canthaxanthin in the diet gave a higher total carotenoid deposition in the flesh than either astaxanthin or canthaxanthin alone in the diet.

Pigmentation of salmonids — A comparison of astaxanthin and canthaxanthin as pigment sources for rainbow trout

Abstract Rainbow trout ( Salmo gairdneri ) were fed a diet supplemented with astaxanthin and canthaxanthin. The ratios of astaxanthin to canthaxanthin were determined in plasma, faeces, and flesh. During 65 days of feeding the flesh reached a level of 4.5 mg carotenoids/kg. A linear relationship between growth and carotenoid level was found for growth rates below 150 g/65 days. Astaxanthin seemed to be absorbed more readily from the diet and also deposited at a higher rate than canthaxanthin in the flesh. The pylorus seems to be the site for absorption of astaxanthin.

Pigmentation of salmonids: Factors affecting carotenoid deposition in rainbow trout (Salmo gairdneri)

Abstract Factors affecting carotenoid deposition in rainbow trout (Salmo gairdneri) were investigated in three feeding experiments. The deposition of astaxanthin in the flesh increased significantly with increasing levels of astaxanthin and fat in the diets. However, increasing levels of astaxanthin in the diet decreased the retention ratio of astaxanthin (astaxanthin in flesh to astaxanthin in diet). Fish size, dietary fat quality and vitamin E supplementation seemed to have no effect on astaxanthin deposition. Depletion of the amount of astaxanthin in the flesh suggests metabolization of deposited astaxanthin.

Pigmentation of salmonids — Genetical variation in carotenoid deposition in rainbow trout

Significant differences in the carotenoid, astaxanthin and cantaxanthin levels were observed between full-sib and half-sib of rainbow trout (Salmo gairdneri). The sex did not affect pigment deposition but a weak negative correlation between fish weight and level of carotenoids in the flesh was found.

Pigmentation of salmonids — Variation in flesh carotenoids of Atlantic salmon

Abstract The aim of the present study was to determine some causes of variation in pigmentation of Atlantic salmon ( Salmo salar ) reared under commercial conditions. At slaughter of one year class of Atlantic salmon, composed of half-sib and full-sib groups, the levels of carotenoids in flesh and ovaries were determined. it was found that the level of carotenoid was influenced by the genetic background of the fish, the stage of sexual maturation and weight. The relative importance of each of these factors is discussed.

Protease activities and carotenoid levels during the sexual maturation of Atlantic salmon (Salmo salar)

Abstract Protease activities in the digestive tract and carotenoid levels in flesh, ovaries and plasma were determined in Atlantic salmon (Salmo salar) in their third sea year during the period from early March until December. Protease activities in the digestive tissues changed significantly during the maturation process: the fish have higher enzyme activities in early maturation and lower in the later stages until maturity. The trypsin-like isozymes were studied by IEF electrophoresis during maturation, and variations observed were possibly genetic. The level of astaxanthin in flesh and ovaries decreased significantly during sexual maturation, but the total amount in the ovaries continued to increase. The covariance between astaxanthin in the plasma and trypsin-like activities in the digestive tissues was significant, and the level of astaxanthin in the plasma was also influenced by time and stage of sexual maturation.