Evaluation of Different Magnesium Concentrations on the Performance of Abalone (Haliotis squamata) Cultured in a Recirculating Aquaculture System

This study examined the effect of magnesium (Mg²⁺) supplementation in a recirculating aquaculture system (RAS) on the growth performance and physiological responses of Haliotis squamata. Four Mg²⁺ concentrations (0, 0.125, 0.250, and 0.375 g L⁻¹) were tested over a 120-day period, using Gracilaria gigas as the sole feed source. The 0.250 and 0.375g L⁻¹ treatments significantly enhanced specific growth rate, final body weight, and shell length of abalone (P< 0.05). Magnesium retention in both meat and shell tissues increased, accompanied by elevated antioxidant capacity, RNA/DNA ratio, and meat pH, particularly at 0.375g L⁻¹. However, this concentration also led to a decrease in meat protein content, alongside increases in moisture and lipid levels. A reduction in seawater Mg²⁺ concentrations confirmed the active ion uptake by abalone. This study proposes an integrated strategy that combines essential mineral regulation with macroalgal-based feeding in a closed-loop system. Such integration improves ionic balance and physiological homeostasis, thereby promoting sustainable and efficient abalone aquaculture. These findings offer a scientific basis for optimizing Mg²⁺ levels in nutrient management strategies for tropical mollusk production.