Effects of Emergence Time and Early Social Rearing Environment on Behaviour of Atlantic Salmon: Consequences for Juvenile Fitness and Smolt Migration

Abstract

Consistent individual differences in behaviour have been well documented in a variety of animal taxa, but surprisingly little is known about the fitness and life-history consequences of such individual variation. In wild salmonids, the timing of fry emergence from gravel spawning nests has been suggested to be coupled with individual behavioural traits. Here, we further investigate the link between timing of spawning nest emergence and behaviour of Atlantic salmon (Salmo salar), test effects of social rearing environment on behavioural traits in fish with different emergence times, and assess whether behavioural traits measured in the laboratory predict growth, survival, and migration status in the wild. Atlantic salmon fry were sorted with respect to emergence time from artificial spawning nest into three groups: early, intermediate, and late. These emergence groups were hatchery-reared separately or in co-culture for four months to test effects of social rearing environment on behavioural traits. Twenty fish from each of the six treatment groups were then subjected to three individual-based behavioural tests: basal locomotor activity, boldness, and escape response. Following behavioural characterization, the fish were released into a near-natural experimental stream. Results showed differences in escape behaviour between emergence groups in a net restraining test, but the social rearing environment did not affect individual behavioural expression. Emergence time and social environment had no significant effects on survival, growth, and migration status in the stream, although migration propensity was 1.4 to 1.9 times higher for early emerging individuals that were reared separately. In addition, despite individuals showing considerable variation in behaviour across treatment groups, this was not translated into differences in growth, survival, and migration status. Hence, our study adds to the view that fitness (i.e., growth and survival) and life-history predictions from laboratory measures of behaviour should be made with caution and ideally tested in nature.

Emergence Time and Skin Melanin Spot Patterns Do Not Correlate with Growth Performance, Social Competitive Ability or Stress Response in Farmed Rainbow Trout

“…An individual, upon facing a stressor, displays a number of consistent behavioral and physiological responses that are characteristic of that individual. These responses are commonly referred to as the stress-coping style (SCS) (Koolhaas et al, 1999 ; Larsen et al, 2015 ). Within a continuous range of SCSs, two well differentiated extremes have been characterized, the reactive and proactive SCS (Larsen et al, 2015 ).…”

Bolder guppies do not have more mating partners, yet sire more offspring

“…An alternative explanation was that personality traits could influence an individual’s fitness, and in the last few decades researchers have indeed found some evidence for associations between personality traits and fitness components (reviewed in [5]). Both, studies supporting such associations [6–8], as well as not [9–11], have been published to date, and thus no consistent pattern of the general effect of personalities on fitness has yet emerged.…”

Proactive coping style in early emerging rainbow trout carries a metabolic cost with no apparent return

“…The behavioural response of individual fish to stressful or unfamiliar conditions is correlated to their personality (Ruiz-Gomez and Huntingford, 2012;Larsen et al, 2015). On the personality continuum, extreme behavioural types occur at relatively low frequencies, while the majority of a population occupies intermediate positions (Wolf et al, 2007).…”

“…For salmonids, the stress coping style of an individual has been shown to be correlated with the time of emergence from the gravel spawning nest (Vaz-Serrano et al, 2011;Andersson et al, 2013a). Early emerging individuals have been shown to be bolder and more aggressive (Metcalfe and Thorpe, 1992;Metcalfe et al, 1995), be less sensitive to confinement stress (Larsen et al, 2015), and have shorter feeding latencies and higher feeding rates (Vaz-Serrano et al, 2011), than late emerging individuals. Furthermore, a positive correlation has been shown between boldness and activity levels (Larsen et al, 2015).…”

“…Selecting rainbow trout based on their emergence time could therefore be a potential way to obtain fish with improved stress coping ability and higher growth potential. The bioenergetic, territorial and behavioural profiles have, to some extent, been described for early and late emergers (Brännäs, 1995;Larsen et al, 2015). Additionally, some production related studies have been conducted, focusing on how fish from different emergence fractions handle crowding or other stressful conditions (Trenzado et al, 2006;Van de Nieuwegiessen et al, 2010).…”