ABSTRACT
Imprinting, an early learning process that can determine later preferences for particular types of stimuli, is usually not a consideration inmany activities related to fish. However, disruption of such learning and/or absence of suitable conditions for the development of preferences are frequent despite the lack of appropriate knowledge regarding theeffects that these practices may have on later behaviour and health. The present study reviews the phenomenon of imprinting in fish and discusses its possible influence on fish welfare. Although there isalso potential for acoustic imprinting, here we discuss how sexual, filial and olfactory imprinting should be considered when addressing welfare issues in fish. The review focuses on the relatively few fish speciesin which this phenomenon has been mainly researched, the results often proving that it may affect some behaviour patterns and social preferences. A diversity of factors, including species, context, behavioural repertoire and social systems may affect the actual existence of the phenomenon, although conditions normally prevailing in husbandry and other systems are not adjusted to allow the emergence of the process. Likewise, the effects of imprinting (or its absence) on fish welfare have still to be demonstrated in manyfish species and should constitute a matter for further studies. The conclusion is drawn that much more needs to be learned. However, a better understanding of the relationship between this early learning processin fish and welfare is essential if a complete analysis of conditions promoting fish welfare is to be made.