Understanding the hatchery stages of shrimp: From Nauplii to Post larvae

Shrimp reproduction begins when females release eggs, which are fertilized externally by males. These eggs are small, transparent, and hatch within hours under optimal conditions. Broodstock must be disease-free, strong-shelled, and properly disinfected (e.g. with 50–100 ppm formalin for 1 hour) to prevent pathogen transfer. Eggs and nauplii are thoroughly washed before entering hatching or larval rearing tanks.

Nauplii are the first larval stage and do not feed, as they lack a mouth and digestive tract. They rely on their yolk sacs for nourishment and molt every 3–5 hours, passing through six substages. During this period, foundational organs begin to develop. No feed is needed, but stable water conditions are essential. Nauplii are typically stocked at 50–100 individuals per liter.

Zoea larvae have elongated bodies with appendages for swimming and feeding. They begin consuming live feeds like microalgae and are gradually introduced to formulated micro-encapsulated diets (5–30 µm). This phase is critical; poor nutrition can lead to Zoea II syndrome, a condition linked to high mortality. High feed particle density and stable water parameters are crucial.

Mysis shrimp resembles miniature adults, with improved swimming and feeding abilities. They continue to consume live feeds (e.g. enriched Artemia) and are transitioned to larger formulated feeds (30–90 µm). At this stage, nutritional needs increase, requiring 50–60% protein, 10–15% lipids, and essential fatty acids like DHA and EPA. Proper feeding supports the energy demands of metamorphosis into post larvae, and to ensure high survival of good quality PLs.

Shrimp larvae are highly sensitive to water parameters. Ideal conditions include temperatures between 28–31°C, salinity at 30–32 ppt, pH from 7.5–8.5, and dissolved oxygen above 5 ppm. Toxic ammonia (NH₃) must remain below 0.1 ppm. Sudden changes in conditions can cause stress or mass mortality, making consistent monitoring essential.

Traditional live feeds like Artemia are widely used but pose risks such as pathogen introduction and inconsistent nutrition. Recent trials show that partial or full replacement of Artemia with high-quality formulated diets can increased significantly survival. Feed types include microencapsulated, micro bound, and liquid diets enriched with essential vitamins, amino acids, and fatty acids.

After the mysis stage, larvae transform into PL1 and are typically reared indoors until PL5, then moved to nursery tanks for grow-out. Proper hatchery management, broodstock care, water quality control, biosecurity, and nutrition ensure the production of strong, disease-resistant post larvae ready for farming.

Post-larval shrimp exhibit increased resistance after molting due to various physiological and structural changes. During molting, the shrimp sheds its old carapace in exchange for a new, initially soft carapace that allows for growth through water absorption. 

The nutrition of marine larvae involves an understanding of the behavioral, mechanical and physiological processes of feeding in the target animal. The physiology of the gut and gut enzymes also changes and, since transit times may be quite short, designing a nutritious, easily digestible diet is a challenge. The optimal dietary protein levels in larval diets can be expected to vary with species, larval stage, protein source, digestibility and amino acid composition.  Both DHA and EPA are essential for the normal growth and development of many species of marine fish and crustaceans.

The hatchery stages of shrimp—from nauplii to mysis—are pivotal in shaping their early development and eventual transition to adulthood. Each stage presents unique challenges and opportunities, particularly concerning nutrition and environmental conditions. By understanding these stages, aquaculturists can optimize conditions to foster healthier shrimp populations, contributing to sustainable aquaculture practices globally.