Hatchery conditions do not negatively impact respiratory response of early life-stage development in Australian hybrid abalone

On Australian aquaculture farms, early life stages of abalone are reared under controlled abiotic and biotic conditions in an attempt to optimize individual growth and reduce potential stressors. Yet, physiological responses to the rearing conditions are largely unknown. This study tests if commercial stocking densities, light conditions, and oxygen levels influence the oxygen consumption rate (ṀO₂) of early life stages of Haliotis rubra and Haliotis laevigata hybrids at a standard commercial hatchery temperature of 16°C. Oxygen consumption rate of fertilized eggs and larvae in the trochophore, mid-veliger, and early benthic veliger stages were measured at densities from 100 to 2,400 individuals/ml, in light and dark conditions and oxygen levels of 100%–0% air saturation (%O₂sat). Neither density nor light conditions affected ṀO₂ of any of the tested life stages. Normoxic ṀO₂ varied across developmental stage and was higher in the actively swimming mid-veliger stages (114.92 ± 2.68 pmol O₂/ind/h) in comparison with less active earlier (49.48 ± 2.33 pmol O₂/ind/h) and later life stages (65.90 ± 3.05 pmol O₂/ind/h). Critical oxygen tensions, taken as the point at which animals could no longer maintain ṀO₂, ranged from 22.7% ± 2.7%O₂sat in fertilized eggs to 14.0% ± 1.0% O₂sat in mid-veliger larvae. These results suggest that current conditions in Australian abalone aquaculture farms should not negatively impact the development of early life stages of hybrid abalones.