White Muscle in Shrimp

By Dr. Wiphada Mitbumrung, Ph.D. Applied Marine Biosciences — Wed May 20 2026

White muscle is a common field observation in shrimp farming, especially in hatchery and grow-out systems. It is characterized by white, cloudy, or opaque patches in the abdominal muscle, most commonly seen in the tail section. The affected muscle may appear as white bands or patches, especially around the middle abdominal segments. In some cases, shrimp may show weak swimming, slow response, poor feeding, or mortality.

Possible Causes of White Muscle in Shrimp

The major causes of white muscle in shrimp include:

Mineral deficiency
Bacterial infection, especially Vibrio or Aeromonas
Microsporidiosis
Viral infection, especially IMNV
Environmental stress

Among these, mineral deficiency is one of the most common field-related causes of temporary white muscle, especially when the problem appears after pond stress such as heavy rain, sudden dilution of salinity, low oxygen, or molting events.

White Muscle Caused by Mineral Deficiency

Shrimp requires key minerals such as sodium, potassium, calcium, and magnesium to maintain water and salt balance inside the body. These minerals are important for osmoregulation, nerve function, muscle contraction, molting, shell strength, and energy metabolism.

(White muscle shrimp found on feeding tray, photo by Blue Aqua Breeding Center)

When minerals in pond water or feed are insufficient or imbalanced, shrimp may lose proper osmotic balance. As a result, water movement inside the muscle becomes disturbed. The muscle can tighten, cramp, or lose normal function, causing the tissue to appear white or cloudy.

Calcium and magnesium are especially important for nerve and muscle movement. When these minerals are low, shrimp muscle may contract abnormally, leading to stiffness and white muscle appearance. Trace minerals also support energy production and antioxidant protection. If trace minerals are deficient, shrimp become less able to manage oxidative stress, and muscle tissue can be damaged more easily.

This type of white muscle is often temporary and reversible if the cause is corrected quickly. In field conditions, white muscle caused by mineral deficiency is commonly associated with:

White patches in the abdominal muscle
Slower swimming
Weak response
Soft shell or incomplete molting
Reduced growth
Poor recovery after stress
Occurrence after heavy rain or sudden salinity drop

Environmental Stress as a Trigger for White Muscle

Environmental stress can trigger white muscle when shrimp are unable to maintain normal osmotic balance, muscle function, and energy metabolism. Stressors such as low dissolved oxygen, sudden salinity or temperature changes, heavy rain, molting, transport, and high stocking density increase the shrimp’s demand for oxygen and minerals. Heavy rain or sudden water exchange can dilute salinity, alkalinity, hardness, calcium, magnesium, and potassium, making shrimp more vulnerable to muscle cramping, weakness, and white muscle. Low oxygen reduces energy production, while molting and handling stress increase mineral demand. Under high-density conditions, chronic stress, organic waste, and bacterial pressure further weaken shrimp, making white muscle more likely to appear and increasing the risk of secondary infection and running mortality.

(Stress triggered white muscle, photo by Dr.Anand PR)

White Muscle With Mortality

When white muscle is observed together with mortality, the case should be taken more

(Shrimp infected with IMNV, photo by Dr.Anand PR)

The first pathway is mineral deficiency followed by secondary infection. Mineral imbalance weakens shrimp physiology, reduces stress tolerance, and compromises immune defense. Once shrimp are weakened, they become more susceptible to opportunistic pathogens such as Vibrio, Aeromonas, or viral infection. In this situation, white muscle may start as a stress or mineral-related problem, but mortality occurs because secondary infection develops.

The second pathway is severe infection itself. Some Vibrio infections can directly cause serious tissue damage, weakness, and mortality. Vibrio is more commonly associated with high-salinity culture conditions, while Aeromonas is more commonly associated with low-salinity culture systems. However, both bacteria can become problematic when pond conditions are unstable, organic load is high, or shrimp are stressed.

IMNV is another important cause of white muscle, especially when white muscle is associated with disease spread and mortality. IMNV typically affects muscle tissue and may cause white or necrotic muscle areas. Confirmation requires PCR testing because clinical signs alone are not enough to separate IMNV from mineral deficiency, bacterial infection, or other muscle disorders.

Microsporidian parasites can also cause white muscle-like lesions. In these cases, the white muscle area may appear as a white lump during dissection. The affected shrimp may show localized muscle opacity, poor growth, weakness, and chronic infection signs. Microscopic examination is needed to confirm the presence of spores or parasite stages.

Therefore, white muscle with mortality should not be assumed to be only mineral deficiency. It should be investigated together with bacterial count, Vibrio condition, water quality, and PCR testing for major shrimp

Field Observation and Diagnosis

White muscle can be difficult to notice from the pond surface because many weak or dead shrimp may sink and remain underwater. Farmers should check shrimp regularly from feeding trays, cast net sampling, and pond edge observation.

Important field signs include:

White, cloudy, or opaque muscle
White bands or patches in the tail section
Weak swimming or slow response
Reduced feeding
Soft shell or molting problem
Sudden mortality after rain or water exchange

Management Strategy

Management should depend on the confirmed or suspected cause.

If the problem is related to mineral deficiency, the main strategy is to restore mineral balance quickly. In this case, MinGro can be used as a practical solution to supply essential bioavailable minerals to the pond water. A higher corrective dose, around 10 ppm, can be applied when white muscle is clearly associated with mineral deficiency, stress, heavy rain, or salinity dilution.

The objective is to help shrimp recover osmotic balance, improve muscle function, support molting, and strengthen stress resistance. Mineral correction should be combined with stable water management, proper aeration, and reduced handling stress.

If mortality is present, farmers should not rely on mineral correction alone. They should also check for Vibrio, Aeromonas, IMNV, and other pathogens. If bacterial infection is involved, pond organic load should be reduced, water quality should be stabilized, and suitable probiotics or bacterial control strategies should be used. If viral infection is confirmed, farm management should focus on biosecurity, reducing stress, preventing spread, and avoiding movement of infected shrimp or water to other ponds.