Analysis of Respiratory Behaviour of Thicklipped Grey Mullet (Chelon labrosus) Juveniles Under Different Rearing Conditions

Thicklipped grey mullet (Chelon labrosus) shows potential as an appealing species for aquaculture in the EU. Knowledge of its metabolic requirements is essential for species management and control of environmental conditions. We examined routine and postprandial oxygen consumption (OC) in juveniles as a function of body weight (Bw: 2–85 mg) and temperature (T: 14–26 °C), as well as OC and ventilatory frequency (VF) under gradual hypoxia as a function of T (14–22 °C). Multiple regression analyses determined the effects of Bw and T on mean daily (OCmean), postprandial (OCSDA), routine (OCroutine), and maximum (OCmax) levels, as well as on OCmax/OCroutine ratio (MSF), postprandial OC duration (DSDA) and time to reach maximum activity (Dpeak). The effects of dissolved oxygen (DO) and T on OC and of T on initial VF (VFini), maximum VF (VFmax), critical DO threshold (%DOcrit), and VF change threshold (%VFch) were also analysed. All OC levels increased with T and Bw, except MSF, DSDA, and Dpeak, uninfluenced by Bw. Under gradual hypoxia, OC decreased with falling DO, more sharply at higher T, consistent with oxyconformer behaviour. VF remained stable until 50% DO, then rose progressively, reaching higher VFmax at higher T. Simulations using derived equations estimate C. labrosus respiratory response and water flow requirements under aquaculture conditions.