Metabolic Rate of Goldfish (Carassius auratus) in the Face of Common Aquaculture Challenges

This study examined the metabolic rate (MO₂, oxygen consumption) of goldfish (Carassius auratus) under normal management conditions in aquaculture. Using an intermittent respirometry system, we assessed daily variations and the effects of feeding, handling, temperature increase, and anesthetics. MO₂ exhibited a daily rhythm, with higher values during day. Feeding to satiety produced a 35% increase in MO₂ compared to fasted animals, with a maximum peak after 3 h and returning to baseline after 7 h. Handling stress (5 min) produced a 140% MO₂ peak (from 180 to 252 mg O₂ kg^-1 h^-1), returning to the routine MO₂ after 2.5 h. An increase in water temperature (+0.1 °C min^-1) up to 30 °C caused MO₂ to peak at 200% after 2.5 h from the start of the temperature increase. The use of common anesthetics in aquaculture (MS-222, 2-phenoxyethanol and clove oil in deep anesthesia concentration) affects MO₂ during the first few minutes after anesthetic recovery, but also during the following 4 h. It can be concluded that the metabolic rate is a good indicator of the goldfish's response to aquaculture practices involving energy expenditure and stress. Thus, intermittent respirometry is a valuable non-invasive tool for understanding and improving fish welfare in aquaculture.