Water temperature is one of the most critical environmental parameters affecting fish physiology, behavior, and welfare in aquaculture systems.
Water temperature affects virtually every aspect of fish welfare in aquaculture. Outside the optimal thermal range, fish experience physiological stress evidenced by elevated cortisol, reduced immune function, increased disease susceptibility, and behavioral changes including reduced appetite and abnormal schooling. In net pen systems, fish cannot escape thermally stressful conditions when warm surface water layers form, concentrating into cooler deeper water that may be oxygen-depleted. This creates a welfare trap where fish must choose between thermal stress and hypoxic stress. Sub-optimal temperatures also impair wound healing, meaning injuries from lice, handling, or crowding take longer to resolve. Precision temperature management through deep water cooling pipes or shelter areas represents an important welfare improvement for thermally stressed populations.