Investigating fear in rainbow trout (Oncorhynchus mykiss) using the conditioned-suppression paradigm
Trout learned the operant task of pendulum-pressing for a food-reward in a mean of 4.3 sessions lasting 1 hr. In a separate phase, fish also learned–through classical conditioning–to associate a neutral light cue with an aversive stimulus. When again allowed to pendulum-press for food, after aversive classical conditioning, there was a drop in the rate […]
Effect of noxious stimulation upon antipredator responses and dominance status in rainbow trout
A potentially painful experience may modify normal behavioural responses. To gauge the importance of pain relative to predation or social status, we presented competing stimuli, a predator cue or an unfamiliar social group, to two groups of noxiously treated rainbow trout, Oncorhynchus mykiss. In the predator cue experiment, fish were classified as bold or shy. […]
A comparison of aggressive and foraging behaviour between juvenile cutthroat trout, rainbow trout and F1 hybrids
‘Successful’ introduced species are often thought to cause declines or extinctions of native species through competitive superiority. In western North America, introduced rainbow trout, Oncorhynchus mykiss, have completely replaced many native cutthroat trout, Oncorhynchus clarkii, populations; however, few studies have identified the mechanisms that may allow rainbow trout to outcompete cutthroat trout. We raised Yellowstone […]
The effect of elevated blood cortisol levels on the extinction of a conditioned stress response in rainbow trout
Following previously published observations that a conditioned response (CR) was lost more quickly by rainbow trout (Oncorhynchus mykiss) exhibiting a high responsiveness to stressors than by low responding individuals this study was designed to investigate the effects of exogenous cortisol on the retention of a CR in unselected rainbow trout. Fish held in isolation were […]
Plasticity of Boldness in Rainbow Trout, Oncorhynchus mykiss: Do Hunger and Predation Influence Risk-Taking Behaviour?
Boldness, a measure of an individual’s propensity for taking risks, is an important determinant of fitness but is not necessarily a fixed trait. Dependent upon an individual’s state, and given certain contexts or challenges, individuals may be able to alter their inclination to be bold or shy in response. Furthermore, the degree to which individuals […]
Effect of food abundance on aggressiveness and territory size of juvenile rainbow trout, Oncorhynchus mykiss
How food abundance affects (1) whether or not individuals defend territories and (2) what size of territory is defended are crucial to understanding the role that territoriality plays in regulating the population size of stream-dwelling salmonids. The threshold model of feeding territoriality predicts that territorial defence will be most intense at intermediate levels of food […]
Environmental change alters personality in the rainbow trout, Oncorhynchus mykiss
Boldness is a personality trait that defines how individuals respond to risky situations and has clear fitness consequences. Since the adaptive value of boldness is context dependent, the benefit of a distinct personality is less clear when the environment is unpredictable. An ability to modulate behaviour can be beneficial, although as behavioural plasticity itself may […]
Does environmental enrichment promote recovery from stress in rainbow trout?
The EU Directive on animal experimentation suggests that all protected animals should have enrichment to improve welfare yet relatively little research has been conducted on the impact of enrichment in fish. Studies employing enrichment in zebrafish have been contradictory and all fish species should be provided with species-specific enrichments relevant to their ecology. Salmonids are […]
Rapid recovery of the cortisol response following social subordination in rainbow trout
Rainbow trout (Oncorhynchus mykiss) confined in pairs form social hierarchies in which distinctive behavioural and physiological phenotypes distinguish dominant from subordinate fish. In particular, subordinate fish are characterized by inhibition of behaviours such as feeding and activity, by low growth rates, and by chronic elevation of circulating glucocorticoid stress hormone (cortisol) concentrations. To evaluate the […]
Dietary self-selection in fish: a new approach to studying fish nutrition and feeding behavior
The principles of modern aquaculture encourage the development of fish feeds containing low fish meal content and several types of plant ingredients plus nutrients to avoid depleting global fish stocks and to reduce costs. However, food constituents can affect animal nutrition and feeding behavior, so the effect of different diets on fish behavior and growth […]