Salmonid aquaculture has focused for many years on enhancing the quantity of ®sh produced. However, optimization of the quality of salmonids may lead to improved consumer acceptance and higher prices for the farmed product. The present review evaluates how the quality of salmonids is affected by parameters such as feed type, level of dietary intake (ration) and growth. Feed composition has a major in¯uence on the proximate composition of salmonids. In particular, whole body lipid as well as the lipid content in the edible ®llet is directly related to dietary fat content, while the fatty acid composition of the ®sh¯esh is also strongly in¯uenced by the dietary fatty acid pro®le. While ®sh body composition appears to be largely in¯uenced by feed composition, an increase in other parameters such as feed ration and ®sh size also results in enhanced adipose deposition and decreased water content in the ®sh body. The protein content, however, remains more or less stable. An increase in ®sh body lipid content is not necessarily a negative factor, depending upon the processing procedure that follows. However, an increase in body fat content is generally accompanied by a reduction in slaughter yield, owing to an increase in the weight of viscera in relation to body weight. Although salmonid¯esh quality with respect to levels of proximate constituents and yield appears to be under the strong in¯uence of feed composition and feed amount, the sensory characteristics, such as odour,¯avour, texture, etc., are only governed by these factors to a small degree. Tactics for the rearing of salmonids for speci®c purposes should therefore take into consideration the fact that the level of proximate constituents in the whole body as well as the ®llet are readily manipulated by feed composition and feeding strategies, whereas the sensory parameters are less affected by these variables.

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Rainbow trout were studied at different rearing densities, fish sizes and feeding frequencies so that we could evaluate the effect of these parameters on fin condition, growth and feed utilisation. In one study, two sizes of rainbow trout (18-70 g or 48-125 g), fed to near satiation at 17.7°C, were examined at two rearing densities (11-41 kg m -3 or 21-92 kg m -3 ). This study showed that the anal fin was healthier (P < 0.05) at low densities. In the second study rainbow trout were again fed to near satiation and grown from 50 g to 125 g in 16.4°C water, and they were fed either once daily or three times daily at two densities (18-45 kg m -3 or 54-124 kg m -3 ). Rainbow trout growth and feed utilisation were slightly but significantly (P < 0.05) reduced at high densities, while dorsal fin condition, surprisingly, was better (P < 0.0001) at the high densities. Possible explanations to these findings are discussed. Condition of the left pectoral fin was improved at once daily feeding (P < 0.05) compared with three feedings per day, at which fights for feed possibly are more frequent.

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