Oxygen consumption and growth of the orange-spotted grouper Epinepheluscoioides larvae under different feeding regimes

Growth and metabolic rates during early development of Epinepheluscoioides was studied to better elucidate the physiological processes that may optimize grouper larval rearing and improve seed production. Patterns in growth and oxygen consumption, used as an index of metabolic rate, of E. coioides during critical periods of high mortality in larval rearingwere described for three feed treatments (unfed, natural food only and co-fed artificial diet). Growth was determined by measuring total length and dry weight. Oxygen consumption was measured using an intermittent-flow system.Specific growth rates of larvae both fed natural food only and co-fed artificial diet peaked on days 3, 6, 19 and 33;highest on day 19 at 24% and 11.6%, respectively. These accelerated rates coincided with the stages of hatching, transition from endo- to exotrophy, inflation of the swimbladder and pre-metamorphosis. Negative specific growth rates were noted between days 1 and 4 for both treatment groups as well as a more acute decline on day 33 for the co-fed treatment group.Growth depensation(where large larvae grow larger and the small larvae lag further behind) was noted with increasing coefficient of variation (dry weight). Cannibalism was validated among larvae fed natural food only on day 33 by the computed maximum larval sizes well-above the 30% threshold size difference characteristic of cannibals.However, day 33 larvae co-fed artificial diet,observed to have significantly reduced standard metabolic rate, may have experienced a different cause for death other than cannibalism(such as suboptimal nutrition) as only the largest sizes experienced mortality.