01 · AquaGrow
What it is
An empty gut is an observation, not proof of infection or hunger alone. Newly hatched nauplii use yolk reserves; zoea is the first feeding stage. Assess the actual stage, water, feed and animal condition together.
Signs to watch for
- Weak or unusual swimming.
- Less gut content than expected for the stage and feeding time.
- Poor feed response or declining survival.
Common causes
- Feed quantity, size, quality or timing does not suit the stage.
- Water or oxygen conditions interfere with normal feeding.
- Illness or handling stress affects the larvae.
How to confirm the cause
- Have trained staff examine representative larvae promptly under a microscope and record stage and sampling time.
- Check feed availability/quality and water readings. Arrange diagnostic assessment if the decline persists.
What to do immediately
- 1
Check air supply, DO and recent water changes before increasing feed.
- 2
Ask the technician to verify the stage and examine larvae and live feed.
- 3
Keep feed lots identified; stop a suspected unsuitable feed lot rather than adding more of it.
- 4
Use a stage-specific feeding adjustment and monitor recovery. Do not impose a prolonged blanket feed stop on delicate feeding stages.
Prevention: your practical checklist
- Match feed to observed stage and consumption.
- Check live-feed cultures and feed storage.
- Record feeding time, observations and survival so changes are noticed early.
When to call an expert
- Get urgent help for weakness with deaths, abnormal water or rapid decline.
- Arrange assessment if feeding does not recover after a verified management correction.
Farmer questions
Does an empty gut prove bacterial disease?
No. Feed access, stage, sampling time, water and health can all affect the observation. Use trained examination and the wider records.
Should I simply add more feed?
Not before checking why feeding is poor. More uneaten feed can increase waste. Let the technician adjust feed for the actual stage and condition.
Can I compare samples taken at different times?
Timing can change gut observations. Record stage, recent feed and sampling time and use a consistent assessment method.
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.
- P. vannamei digestive development across larval stages (2020) ↗Rojo-Arreola and colleagues, PLOS ONE; original research, not a treatment trial
- Microbial communities associated with zoea-2 syndrome (2023) ↗ICAR-CIBA authors, Frontiers in Marine Science; association study, not proof of a single cause
- SHAPHARI hatchery operating guidelines — production, biosecurity and records ↗MPEDA; linked guideline, not AquaGrow certification or a legal-compliance audit