Abstract
This study examined the metabolic rate (MO(2), 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. MO(2) exhibited a daily rhythm, with higher values during day. Feeding to satiety produced a 35% increase in MO(2) 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% MO(2) peak (from 180 to 252 mg O(2) kg(-1) h(-1)), returning to the routine MO(2) after 2.5 h. An increase in water temperature (+0.1 °C min(-1)) up to 30 °C caused MO(2) 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 MO(2) 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.