Optimal Time to Harvest Brine Shrimp (Artemia salina) Nauplii as Live Food for Aquatic Animals

Brine shrimp (Artemia salina) are commonly utilized as aquatic live food, but only a few studies have investigated the optimal harvesting time. In the present study, brine shrimp eggs were hatched in artificial seawater and harvested at different periods (22, 24, 26, 28, 30, 32, 34, and 36 h). Harvested nauplii from quadruplicate tanks were analyzed for total carotenoid content, digestive enzyme activities, proximate chemical composition and fatty acids. Economically significant fish were used to test in vitro digestibility using their digestive enzymes. Total carotenoid contents significantly decreased with post-hatch time as the equation y = –0.0108x + 0.6265 (p < 0.05, –65.3% of final value). The trypsin-specific activity was elevated in brine shrimp harvested at 26 to 36 h and was lowest at 24 h (p < 0.05). However, there was no difference in the specific activities of chymotrypsin, lipase, and amylase over the eight harvesting periods. Ash contents were significantly lower at 34 to 36 h after hatching, compared to earlier times. Crude lipid contents fluctuated without showing a trend. In the fatty acid profile, levels of highly unsaturated, monounsaturated, polyunsaturated fatty acids, omega-3 and omega-6, were highest at 22 h after hatching. In vitro digestibility indicated suitable times for feeding out brine shrimp to guppy (22 h), striped catfish (22 to 24 h), Nile tilapia (22 to 26 h), and swordtail (22 to 30 h). Our investigation of the optimal time for harvesting brine shrimp as live food will help improve the quality of aquaculture produce.