Neurobiology of Wild and Hatchery-Reared Atlantic Salmon: How Nurture Drives Neuroplasticity

Abstract

Life experiences in the rearing environment shape the neural and behavioral plasticity of animals. In fish stocking practices, the hatchery environment is relatively stimulus-deprived and does not optimally prepare fish for release into the wild. While the behavioral differences between wild and hatchery-reared fish have been examined to some extent, few studies have compared neurobiological characteristics between wild and hatchery-reared individuals. Here, we compare the expression of immediate early gene cfos and neuroplasticity marker brain-derived neurotrophic factor (bdnf) in telencephalic subregions associated with processing of stimuli in wild and hatchery-reared Atlantic salmon at basal and 30 min post (acute) stress conditions. Using in situ hybridization, we found that the expression level of these markers is highly specific per neuronal region and affected by both the origin of the fish, and exposure to acute stress. Expression of cfos was increased by stress in all brain regions and cfos was more highly expressed in the Dlv (functional equivalent to the mammalian hippocampus) of hatchery-reared compared to wild fish. Expression of bdnf was higher overall in hatchery fish, while acute stress upregulated bdnf in the Dm (functional equivalent to the mammalian amygdala) of wild, but not hatchery individuals. Our findings demonstrate that the hatchery environment affects neuroplasticity and neural activation in brain regions that are important for learning processes and stress reactivity, providing a neuronal foundation for the behavioral differences observed between wild and hatchery-reared fish.

Effect of handling and crowding on the susceptibility of Atlantic salmon (Salmo salar L.) to Lepeophtheirus salmonis (Krøyer) copepodids

“…This result is in line with the results we obtained in our model of long‐term stress after 5 days of restricted access to surface/overcrowding (except for 2 hr per day). In contrast, shorter durations (30 min to 6 hr) of confinement have been shown to elevate plasma cortisol levels and are considered acute stress conditions (Mes et al., 2018; Sadler et al., 2000). The increase of N:L ratio, indicative of long‐term stress state, observed in experiment 2 may be the result of the increased stocking density in the tank or the surface access restriction or both these factors together.…”

Acclimation effect on fish behavioural characteristics: determination of appropriate acclimation period for different species

“…In their study, Alekseev et al (2017) reported that behavioural patterns of the hatchery-reared and wild-origin salmon juveniles remained different throughout the testing period, because the behavioural habits acquired under the farming conditions more commonly affected juvenile fish survival in natural environments. Mes et al (2018) confirmed that the hatchery environment affects the brain regions that are responsible for learning processes and stress responses, providing a neuronal foundation for the occurrence of behavioural differences between hatchery-reared and wild fish populations. Meanwhile, S anchez-Gonz alez and Nicieza (2017) indicated that morphological changes in hatchery-reared fish leading to convergence with native fish are mediated by phenotypic plasticity and are not the outcome of wild-like phenotype selection.…”

“…Although the salmonids ( O. mykiss and S. salar ) tested in the present study slightly differed in size, their behavioural patterns were similar.Fish farming and holding conditions may be also viewed as factors affecting fish behavioural characteristics. Several studies have been conducted to understand how the neurobiological, physiological and behavioural characteristics of hatchery‐reared fish differ from those of their wild conspecifics (Alekseev et al ., 2017; Mes et al ., 2018; Sánchez‐González & Nicieza, 2017). In their study, Alekseev et al .…”

“…Although the salmonids (O. mykiss and S. salar) tested in the present study slightly differed in size, their behavioural patterns were similar.Fish farming and holding conditions may be also viewed as factors affecting fish behavioural characteristics. Several studies have been conducted to understand how the neurobiological, physiological and behavioural characteristics of hatchery-reared fish differ from those of their wild conspecifics (Alekseev et al, 2017;Mes et al, 2018;S anchez-Gonz alez & Nicieza, 2017). In their study, Alekseev et al (2017) reported that behavioural patterns of the hatchery-reared and wild-origin salmon juveniles remained different throughout the testing period, because the behavioural habits acquired under the farming conditions more commonly affected juvenile fish survival in natural environments.…”

Can juvenile Baltic sturgeon ( Acipenser oxyrinchus ) smell the enemy?

“…In a recent study (Camara-Ruiz, Santo, Gessner, & Wuertz, 2019), an increase of neuroplasticity markers in fish that were trained to feed prey buried in the sand compared to fish that were not trained was observed. Among these markers pcna, neuroD and bdnf are established markers for neuronal activity and neurogenesis and have been used as tools to understand how external stimuli influence the brain (Dunlap, 2014(Dunlap, , 2016Mes, Krogh, Gorissen, Mayer, & Vindas, 2018). Neuropeptides such as brain-derived neurotrophic factor (bdnf) promote neurogenesis, neuron survival and differentiation as well as synaptic plasticity, thereby modulating the brain in response to the rearing environment (Ebbesson & Braithwaite, 2012;Mattson, Maudsley, & Martin, 2004;Shors, Anderson, Curlik, & Nokia, 2012).…”