In this paper, we show the results from four different experiments in which
sea bass, maintained under laboratory conditions, could choose between two
or three different diets through self-feeders, which gradually increased t
he complexity and potential range of selection, to design their own diet in
accordance with their requirements. At first, sea bass were allowed to sel
ect between two complete diets differing in the proportion of protein (52-5
8%): this showed their capacity to distinguish between two diets made of th
e same ingredients. Next, two incomplete diets, containing a fixed amount o
f protein (56%) and lacking either fat or carbohydrate, were made available
. Three mixed diets made up of pairs of macronutrients (protein-carbohydrat
e, protein-fat or fat-carbohydrate) were rested in the next experiment and,
finally, three diets containing only one macronutrient (protein fat or car
bohydrate) were made available to fish. Taking into account selection made
by the fish in the first three experiments, in which macronutrient selectio
n was statistically different, protein was the main macronutrient chosen by
fish (278.15 kJ/kgBW/day, on average), followed by fat and carbohydrate (1
62.85 and 64.56 kJ/kgBW/day, respectively). In conclusion, the results reve
al the ability of sea bass to select an appropriate diet from experimental
diets containing two or three macronutrients and suggest that the proposed
methodology is a powerful tool for studying the differing nutritional needs
of different species of fish.