01 · AquaGrow
What it is
Nauplii are the earliest newly hatched shrimp larvae. A poor hatch may involve egg quality, fertilisation, handling, water or contamination. Counting mistakes can also distort the apparent result.
Signs to watch for
- More unhatched eggs than in comparable batches.
- Weak activity in newly hatched larvae.
- Large differences between hatching tanks or repeated poor results.
Common causes
- Egg or broodstock condition is unsuitable.
- Collection, treatment or water handling differs from the validated procedure.
- Contamination or counting and timing errors affect the result.
How to confirm the cause
- Record the broodstock source, egg and nauplius counts, timing and water readings.
- Use trained visual/microscope assessment; request laboratory advice if health concerns arise.
What to do immediately
- 1
Keep the hatching lot identified and separate from other lots.
- 2
Ask the technician to check water, hatching conditions, observation timing and the counting method.
- 3
Assess nauplius quality before stocking the next stage. Do not blend weak lots into a good lot to hide a poor hatch.
- 4
Review any recent input or treatment event before repeating the same procedure.
Prevention: your practical checklist
- Follow documented collection, water-release and hatching checks.
- Keep broodstock-to-egg-to-nauplius links.
- Use consistent sampling and counting methods across batches.
When to call an expert
- Get prompt help for repeated poor hatches, widespread weak nauplii or suspected contamination.
- Treat rapidly increasing losses or an abnormal water event as an emergency.
Farmer questions
Does a low hatch prove a disease?
No. Egg quality, fertilisation, water, procedures and counting all need review. Laboratory tests should be selected from the investigation, not from a guessed disease name.
Can I combine nauplii from different lots?
Do not mix unresolved weak and healthy lots as a corrective step. Preserve traceability and let the hatchery manager decide movement under the health plan.
Which records are most useful?
Keep the broodstock/lot identity, spawning and collection times, counts, water readings, inputs and observations. Record what was actually measured rather than reconstructing numbers later.
Sources & further reading
AI-assisted educational content and translations, source-checked 17 October 2026. Not an individual diagnosis or prescription. Independent aquaculture-health and native-language specialist approvals have not been supplied. Sources do not endorse AquaGrow.
- SHAPHARI hatchery operating guidelines — production, biosecurity and records ↗MPEDA; linked guideline, not AquaGrow certification or a legal-compliance audit
- Hatchery operations and assessment framework (2007) ↗FAO FTP 446; historical P. monodon manual, not a vannamei treatment protocol