Tese de doutoramento, Ciências do Mar, da Terra e do Ambiente, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016The reason why some individuals from the same fish population react so differently under
similar aquaculture husbandry practices or to any other stressful situation is at the core of
today’s fish welfare research. In this context, the large individual variation in the
physiological or behavioural response under stressful conditions is now accepted as
reflection of distinct personality traits and of divergent cognitive evaluation that the
individual makes of the situation, i.e. on the way the stressor is appraised. This thesis aimed
to uncover which appraisal criteria fish use, the interplay with their personality traits, the
underlying neurophysiological mechanisms and the potential application of psychological
modulators of the stress response to improve fish welfare. Thus, the experimental work was
oriented towards: i) investigating whether pre-existing inherent traits in behaviour and
physiology affect the outcome of exposure to environmental stressors in Gilthead seabream
(Sparus aurata) and Atlantic seabass (Dicentrarchus labrax) (Chapter II.1 and Chapter II.2); ii)
evaluating the effect of predictability on the onset of action-related responses to aversive
and appetitive stimuli (Chapter III.1); iii) inferring how predictability stressor modulates the
cognitive stress response (Chapter III.2); iv) investigating how controllability improves coping
ability on both seabream and seabass (Chapter IV.1); v) examining the relationship between
thermal choice and animal personality using Nile tilapia (Oreochromis niloticus) as model
(Chapter IV.2). Differences in behaviour, physiology and brain states measurements support
specific appraisal and motivations in fish, according to the prospect of reward or
punishment. This seems to be, nevertheless, highly dependent of both species - and contextspecificity.
In addition they suggest that predictable stimuli and social support alongside with
perception of control can be used as psychological modulators of the stress response to
make animals more resilient and empowered under sustainable farming systems. The link
between personality and appraisal deserves further investigation as evidences are narrow.
The work developed in the core of this thesis has brought new insights on how to
manipulate fish´s ability to cope with changes in their environment, ensuring positive
outcomes in terms of welfare, fitness and survival
