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Adapting to fluctuating predation conditions is a challenge for prey. By learning through experience, animals may adjust their anti-predator behavior to better reflect current predation risk. Although many studies show experience of predation to alter prey behavior, little is known about how prey rely on such experience over time. By comparing boldness over different temporal scales between individuals of Eurasian perch, either experienced or naïve of predators, we examine how risk is traded based on past and present experience. Differences in predator exposure during the first year of life were found to lead to differences in risk-taking behavior, even after the perch been kept in a predator-free environment for 9 months. However, the response to a potential predator was quickly readjusted after increased experience of current conditions. The results highlight how prey have to balance past experiences of predators against current threat levels.

The food selection of the common goby, Pomatoschistus microps Krøyer, was studied in the field and in laboratory experiments on the Swedish west coast. The three most important prey organisms for P. microps in the study area were Corophium volutator, chironomid larvae and Nereis spp. Corophium was consumed more than any other prey, even when it was not the most abundant prey species in the bottom. One reason may be the higher activity of Corophium above the sediment surface, which may increase its visibility and consequently its vulnerability to visual predators. When P. microps was offered Corophium and chironomid larvae with similar exposure in laboratory experiments, it showed no preference for either of the prey items. It always took the closest mobile prey, regardless of species and size.

Lately, there has been an increasing interest in intraspecific variation in behaviour, and numerous studies on personality have been performed in a variety of animals, including several fish species. Individuals have been divided into coping style categories or arranged along a behaviour gradient, such as the bold/shy continuum. However, many fish species live in groups, and the social environment can influence the behaviour of an animal in different ways. There may be conflicts within groups due to competition for resources, and dominance hierarchies are commonly found. On the other hand, there are many benefits of consensus decision-making within the group. Conformity of behaviour is probably adaptive, due to the benefit of public information on, for example, food resources and predation risk. Accordingly, studies of fish shoals have found evidence of consensus decision-making. Furthermore, factors in the environment, such as predation risk would also influence the behaviour expressed. To be able to understand behaviour patterns in a group of fish, it is necessary to consider the variation of individual characteristics, and how the group, as well as other environmental factors, affects the behaviour of individuals. Here, I will review studies on different aspects of personality within a social context in fish, with a special emphasis on the Eurasian perch Perca fluviatilis.

The common goby, Pomatoschistus microps, has parental care, with males building nests and guarding the fertilized eggs until hatching. We carried out field experiments to estimate the response of males to predation risk in relation to developmental stage of their brood and time of the season. Artificial nest substrates were placed in a shallow bay with soft substrate. After the nest had been built and eggs laid in it, a glass jar containing a potential predator (an eelpout, Zoarces viviparus) was placed 15 cm from the goby's nest. We subsequently chased the male goby away from the nest and measured his flight distance and time until return. This was repeated once a day in May, June, and August. Time away from the nest decreased in the course of one brood cycle, with a steeper slope in May compared to the other months, as a result of longer times away from the nest in the beginning of the experiment. Flight distance decreased slightly over one brood cycle and was longer in June than in May and August. In another experiment, a male P. microps was presented to the nest-guarding male, simulating a potential competitor for the nest. Again, we found a decrease in return time with advancement of the brood cycle, but the fish returned faster than when facing a predator, especially in the beginning of the brood cycle. No effect of habituation to the treatment was found, but there seemed to be a slight influence of development stage of the eggs. Thus, risk taking by nest-guarding male P. microps appears to be influenced by time already spent guarding one particular brood and the prospect for future reproductive opportunities. [Behav Ecol 1991 ;2:351–359]