Influence of Salinity, Temperature, Photoperiod, and Isochrysis galbana Microalgal Cell Density on the Growth of the Marine Copepod Oithona nana

Copepods play a critical role in aquatic food chains and are a key source of food in aquaculture, so optimizing their culture conditions is essential for their large-scale production. The objective of this study was to determine the optimal culture parameters of the copepod <i>Oithona nana</i> as a function of total population growth and the different stages of its life cycle. To this end, four experiments were carried out in quadruplicate, evaluating the effects of temperature, salinity, photoperiod and optimal microalgal concentration of <i>Isochrysis galbana</i>. Each experiment lasted 15 days. Temperatures of 20, 24, 28 and 32 °C were tested; salinity levels of 20, 25, 30 and 35 PSU; photoperiods of 12L:12D, 16L:8D and 24L:0D; and concentrations of <i>I. galbana</i> of 1 × 10⁴, 5 × 10⁴, 10 × 10⁴, 15 × 10⁴ and 20 × 10⁴ cells/mL. Results indicated that the optimal temperature for the culture of <i>O. nana</i>, with significant differences compared to the other treatments, was 28 ± 1 °C. Regarding salinity, the optimal level for the total development of the population was 25 ± 2 PSU, while to maximize the percentage of copepodites, the most appropriate levels were 30 and 35 PSU. The light-dark regimen of 16L:8D promoted the highest total density of individuals, while 12L:12D and 16L:8D favored development of nauplii and copepodites. Finally, optimal concentrations of <i>I. galbana</i> that generated the highest densities of <i>O. nana</i> at all stages of its life cycle were 15 × 10⁴ and 20 × 10⁴ cells/mL. These findings provide key information for the development of optimized cultures of O. nana, which can improve its availability as a food source in aquaculture systems and favor the success of larval cultures in species of commercial interest.