Changes in Aggressive Behavior, Cortisol and Brain Monoamines during the Formation of Social Hierarchy in Black Rockfish (Sebastes schlegelii)

Abstract

Aggressive interactions can lead to a social hierarchy and influence the responses of animal behavior and physiology. However, our understanding on the changes of fish behavior and physiology during the process of social hierarchical formation is limited. To explore the responses of fish behavior and physiology to social hierarchy, we examined the differences in the growth performance, aggression, cortisol level, brain serotonergic activity, and brain dopamine activity between the dominant individuals and the subordinate individuals of black rockfish (Sebastes schlegelii) in two time scenarios. In the short-term contest, the cortisol level and the ratio of telencephalic 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) was significantly higher in subordinate individuals than in dominant individuals. In the long-term contest, the ratios of 5-HIAA/5-HT in all brain regions were significantly higher, and the frequency of aggressive acts were significantly lower in subordinate individuals than in dominant individuals. In contrast, no difference was detected in growth performance. Significant positive correlations between the cortisol level and serotonergic activity were observed in the short-term contest, but the serotonergic activity was negatively correlated with the aggressive behavior in the long-term contest. These results suggest that subordinate hierarchy inhibits aggression but does not impact growth in black rockfish. The cortisol-related change in brain monoaminergic activity could be a potential indicator to predict aggressive behavior in black rockfish in captivity with an obvious social hierarchy.

Comparing behavioral performance and physiological responses of Sebastes schlegelii with different aggressive strengths

“…In fact, shes form a speci c and self-organized structure during group formation. Therefore, the aggressive behavior of sh in a group context is more re ecting of the real aggression situation (Xu et al 2020). Regrettably, this is challenging to achieve in practice at this stage.…”

“…In general, black rock sh were continuously cultured to over 12 cm under controlled conditions before being released in the coastal seas or moved into nets and were used as a food source and to relieve shing pressure (Guo et al 2017;). The aim of aquaculture is to improve the survival rate of juveniles; however, under intensive culture conditions, black rock sh juveniles display serious aggression and cannibalism, leading to sh welfare and economic loss (Xi et al 2017b;Xu et al 2020).…”

“…Under natural conditions, aggression is an adaptive behavior intended to protect one from harm and conserve resources. However, in intensive aquaculture, cultured shes may have little or no access to escape predation (Metcalfe et al 2016;Xu et al 2020). The most direct impact of aggressive behavior is physical impairment, which in turn in uences the later health and motility of sh (Brandão et al 2018;Castanheira et al 2013;Wolkers et al 2017).…”

“…Fish behavior is a comprehensive representation of extrinsic environmental factors and intrinsic physiological factors (Xu et al 2020). There have been multiple studies on the physiological research of aggressive sh behavior (Ariyomo et al 2013;Boscolo et al 2018), but studies about behavioral performance are scarce.…”

Plasticity of Locomotor Activity Permits Energy Homeostasis During Reproduction in a Female Sea Cucumber

“…We purchased the commercial ELISA Assay Kit from Nanjing Jiancheng Bioengineering Institute (Nanjing, China), and the determination was performed under the manufacturer's guidelines. The ELISA Assay Kit has been validated in many previous studies (Xu et al, 2020).…”