Stress in Fish: Neuroendocrine and Neurotransmitter Responses

Farmed fish face persistent challenges arising from diverse environmental factors and human activities, which induce both acute and chronic stress responses, thereby increasing their susceptibility to diseases and mortality. Therefore, it is essential to comprehend the stressors and corresponding stress responses in fish to recognize and mitigate harmful stress during aquaculture practices. In this review, we provide an overview of the various stressors present in aquaculture, along with the resultant alterations in neuroendocrine responses, including the brain–sympathetic–chromaffin cell (BSC) axis, hypothalamus–pituitary–interrenal (HPI) axis, and caudal neurosecretory system (CNSS), as well as neurotransmitter levels within the nervous system, experienced by fish under different types of stress. Fish possess well-developed nervous and endocrine systems that respond to stress, with complex communication networks among these systems demonstrating distributed collaboration. An understanding of the neuroendocrine and neurotransmitter responses to stress may enhance our comprehension of fish stress mechanisms and facilitate the development of an integrated dietary supplementation strategy and improve their resilience against the diverse stresses encountered in aquaculture.