Optimization of salinity levels for the culture of cyclopoid copepod Dioithona oculata (Farran, 1913) with respect to total population, reproduction, development and adult longevity

Cyclopoid copepod, Dioithona oculata, is a common free-living euryhaline species in tropical and temperate waters having potential as live feed in marine fish larval rearing. Here, the effect of salinity on adult and naupliar survival, total population, population composition, clutch production, clutch size, development rate and adult longevity was investigated. Adult copepods survived the abrupt changes in salinities from 15 to 50 ppt (parts per thousand). The highest naupliar survival was at 30 ppt (86.33 ± 2.84%) and the lowest at 15 ppt (12.6 ± 2.34%). The highest production was at 30 ppt (883.0 ± 5.5 individuals/L) and the lowest at 15 ppt (49.0 ± 6.56 individuals/L). The proportion of nauplii was higher at salinities from 20 to 40 ppt, whereas the total population of copepodites and adults was significantly less at 15 and 45 ppt. The highest clutch production was observed at 30 ppt (8.6 ± 0.54 clutches) and the lowest at 45 ppt (2.6 ± 0.54 clutches). Maximum clutch size of D. oculata was recorded at 30 ppt (19.2 ± 2.94 eggs/clutch) and minimum at 45 ppt (7 ± 1 eggs/clutch) respectively. Development time from nauplius to adult was significantly (p < 0.05) longer at 45 ppt (12.72 ± 0.03 days) and shorter at 20 ppt (9.06 ± 0.02). Adult longevity was significantly higher at 30 ppt (27 ± 1.0 days) and lower at 45 ppt (11.3 ± 1.15). Salinity changes significantly affected the production performance of D. oculata. The optimum salinity for mass culture of D. oculata was found to be 30 ppt.