Effects of Salinity on Reproduction and Survival of the Calanoid Copepod Pseudodiaptomus Pelagicus

Four experiments were conducted on the calanoid copepod, Pseudodiaptomus pelagicus, to determine the effects of salinity on survival, development time, reproductive output, and population growth in order to define the optimal salinity for culture. To determine the appropriate experimental salinity range we exposed nauplii and adults to abrupt salinity changes from 35 g/L to 5, 10, 15, 35, 42, and 48 g/L at 30 °C and determined survival after 24 hours. The second experiment stocked early stage nauplii into 1 L beakers after which they were cultured using standard procedures for 10 days at six salinities (10, 15, 20, 25, 30, 35 g/L); from this survival, sex ratio, time to maturation, and fecundity were measured. The third experiment evaluated the effects of salinity on brood size, brood interval, and nauplii production by stocking individual adult pairs and monitoring nauplii production daily for 10 days. The fourth experiment determined the effects of salinity on population growth and composition of the population produced by stocking 10 adult pairs and culturing them until five days after the first mature adults were observed. Results from the abrupt salinity change experiment showed nauplii survival decreased following abrupt changes in salinity from 35 g/L to \u3c 15 g/L and \u3e 35 g/L. Additionally, adults do not tolerate rapid changes in salinity from 35 g/L to \u3c 15 g/L but are rather tolerant of changes in salinity up to 48 g/L. Survival from early nauplii to adult was not significantly affected by salinity but survival declined at 35 g/L. Time to first maturation and maturation of the entire population was significantly influenced by salinity and took from 6.3 to 9.5 days. In the individual paired adults experiment, salinity significantly affected nauplii production by affecting brood interval and brood size. The percentage of ovigerous females peaked at 20 g/L and declined at salinities above and below this value. When developing production objectives, aquaculturists must consider salinity because of its numerous effects on the culture of P. pelagicus. The optimal salinity range to achieve high survival and the greatest nauplii production is 15–25 g/L