Mortality Diagnosis Chart — Where They Died Tells You Why

When mortality happens, the priority is narrowing down the cause — because different causes call for opposite responses. Checking the following four things resolves most cases. ■ Check 1 — Where did they die? Pond edges, near the surface — likely low oxygen or acute toxicity. The shrimp moved there because they were in distress. Pond bottom — likely disease, especially a chronic progression such as AHPND. It means they lacked the strength to move at all. Clustered around the aerators — low oxygen is close to certain. ■ Check 2 — When did they die? Found at dawn or early morning — suspect low oxygen first. It matches the pattern of oxygen being consumed all night and bottoming out before sunrise. Progressing during daylight — suspect a temperature spike, an inflow of toxic material, or an abrupt water quality change. A few at a time over several days — disease or chronic water quality decline. A steady trickle of daily deaths is the most dangerous signal of all. Right after water exchange or rain — a sudden shift in salinity or temperature, or contaminated inflow water. ■ Check 3 — What is the shell like? Hard shell, intact body — an acute event. Low oxygen or toxicity. The animal was normal right up to death. Soft shell, translucent body — chronic. Disease or nutrition. It had not been eating for some time. Shell half shed — molt failure. Caused by insufficient salinity or minerals (calcium, magnesium) during the molt window, or by low oxygen mid-molt. ■ Check 4 — What about colour and hepatopancreas? Body turned reddish — a sign of severe stress or acute infection. Hepatopancreas pale and shrunken — strongly suspect AHPND. (See post 04.) Black spots on the shell — bacterial shell disease or a fouled bottom. Empty midgut (no dark line along the back) — they stopped eating some time ago. Points to disease. ■ Quick reference Dawn + edges + hard shell → low oxygen Bottom + over several days + pale hepatopancreas → disease such as AHPND Molt period + half-shed shell → molt failure (minerals, oxygen) Right after exchange + sudden and numerous → water quality shift or inflow problem Daytime + abrupt + abnormal behaviour → toxic substance ■ Record mortality counts every day "Feels like more than usual today" is only possible to judge if you have yesterday's numbers. If daily mortality goes from 5 to 12, it still looks small — but it has more than doubled, and that is the moment to act. Once mortality is visibly heavy, it is already too late. Shrimp365 keeps mortality counts alongside water quality and feeding records, so you can look back and see which value moved first, before the deaths started climbing.