Summary A 12‐week feeding trial was undertaken to evaluate the effects of partial replacement of marine raw materials in the diet with soybean meal and beef tallow on growth and product quality of European eel (Anguilla anguilla). Based on growth, feed efficiency and chemical composition, soybean meal was found to be an unsuitable ingredient for eel diets as a substitute for fishmeal (25% on a protein basis), probably because of the low digestibility of its carbohydrate content. However, beef tallow can be used to replace 50% of fish oil without reduction in growth, provided that digestible carbohydrates are present in the diet. No major effects of protein and lipid sources in the diet were found on fillet chemical composition. Sensory analysis revealed no significant differences between fish fed the control and the experimental diets, with the exception of salty taste which was significantly higher in fish fed combined soybean meal and beef tallow compared with fish fed the control diet.

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Fillet yield and chemical composition were evaluated in small, medium and large (about 150, 350 and 700 g, respectively) size classes of sunshine bass (Morone chrysops♀ × Morone saxatilis♂) fed high‐energy diets. Fish size had a major effect on the fillet yield, which was significantly higher (38.8 vs. 33.4–34.6%) in fish belonging to the medium‐size class. The lipid contents of both whole and skinned fillets were higher than those reported in the literature, ranging from 7.8 to 10.6% in whole fillets and from 5.9 to 7.6% in skinned fillets, thereby allowing classification of sunshine bass fed high‐energy diets as a medium‐fat fish. A significant effect of fish size on lipid content was found only for whole fillets, therefore indicating that dietary energy excess in larger fish is mainly stored as subdermal fat. The dietary fatty acid profile was found to be the major determinant of edible muscle lipid composition in all size‐classes considered. The cholesterol content of muscle tissue ranged from 23 to 29 mg/100 g tissue.