01 · AquaGrow
What it is
Shell disease is a practical description of damaged, often darkened cuticle. Opportunistic bacteria can be involved, especially after injury, but a black mark is not a species-level bacterial diagnosis.
Signs to watch for
- Brown or black patches, pits or eroded areas on the shell.
- Darkened or damaged appendages, antenna tips or tail edges.
- Severe cases may include deeper tissue damage, weakness or reduced feeding.
Common causes
- Physical damage can allow shell-eroding microbes to contribute to lesions. Fungal involvement and environmental damage are also possible. This guide concerns live farmed shrimp, not post-harvest blackening of chilled product.
- Similar signs can have other causes: Fungal lesions, injury-related melanisation and environmental irritation. Other causes of body marks; shell colour alone cannot identify a pathogen.
How to confirm the cause
- A professional should assess depth and distribution of lesions and arrange microscopy, culture or tissue examination when needed.
- Check oxygen, nitrogenous wastes, feed access and recent handling. Do not select treatment from a photograph of a black spot.
What to do immediately
- 1
Record lesion location, frequency, feeding response and daily deaths.
- 2
Seek examination if lesions spread, deepen or accompany poor feeding or mortality.
- 3
Correct measured management problems and reassess after moulting with your professional.
- 4
Keep affected stock, equipment and water separate. Agree on safe disposal and any harvest or discharge with your professional.
Prevention: your practical checklist
- Avoid rough netting and unnecessary transfers; maintain gear without sharp or abrasive surfaces.
- Match stocking and feed access to the system’s capacity and prevent injuries from crowding.
- Control feed waste and bottom accumulation, and maintain stable water conditions.
- Assign nets, trays and boots to each pond; clean and disinfect equipment under the farm’s biosecurity plan.
- Keep seed-batch, feeding, water-quality and mortality records so a change is noticed early.
When to call an expert
- Call an aquatic animal health professional urgently if deaths rise, shrimp gather at the surface, or breathing becomes difficult. Check dissolved oxygen while arranging help.
- Arrange an assessment if these signs persist, feeding falls or growth stays behind the crop trend. Send water readings, recent input records and photographs; ask the laboratory how to collect samples.
Farmer questions
Will the next moult solve it?
Some superficial shell damage may be shed, but deeper infection and the conditions causing injury may remain. Keep investigating persistent or worsening cases.
Are black spots on harvested shrimp the same problem?
Not necessarily. Post-harvest melanosis is a separate handling and quality issue. This guide addresses lesions observed in live cultured shrimp.
What should I record before asking for help?
Note the pond ID, culture day, recent deaths, feed intake, water test readings and recent changes. Ask the laboratory about suitable samples before adding a treatment. A photograph alone cannot confirm the cause.
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.
- Better Management Practices for shrimp farms ↗Marine Products Export Development Authority (MPEDA)
- Disease prevention and health management in coastal shrimp culture — interpreting external signs ↗FAO; historical training guidance
- Diseases of Penaeid Shrimps in the Philippines — Shell Disease ↗SEAFDEC Aquaculture Department, Manual No. 16; historical penaeid reference, not treatment instructions