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Symptoms of Hypoxia (Low Oxygen) {{GRAPHIC IMAGE WARNING}}

modified lung

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There was some equipment failure at the fish farm today that caused some mortality due to low oxygen. I thought some people might find pictures of the hypoxia symptoms interesting but I wanted to ask if posting them on here is okay first. Some of the pics are rather bloody and gruesome.



Here we go, Cory approved! 

Diagnosing a fish death directly due to water quality can be tough because the death often occurs with no symptoms at all. However, if there are multiple deaths, some fish usually have one to all of the common symptom. Here's some common symptoms for hypoxia.

Before any of the pictured symptoms start to set in, fish will generally let you know if they're oxygen supply is low in less serious ways. For example, feeding will usually stop, behavior will be lethargic and non responsive, the gills will move rapidly, or the fish with hang near the surface or source of water flow in an unusual way or gulp air, or float upside down.

However, keep in mind these are also all symptoms associated with ammonia and nitrite toxicity, temperature, and pH issues because unhealthy levels of each of these parameters disrupt the ability of fish to absorb oxygen.

One the first serious signs is often a pale discoloration in the gills. Notice the gills fading from red to pale pink to purple/blue/grey:IMG_20220403_110102660.jpg.19ced3098b5b9371f2ddc046b3876d2b.jpgIMG_20220403_110024803.jpg.ceae3899c27cf5e931fc5f2d3ec17376.jpg

The gill filaments will also often appear stuck together which is due to a build of of mucus. A few fish, not pictured, had a mucus buildup so think it was gripping out from under the gill plates like slime:IMG_20220403_105853839.jpg.c01e544b7c1ea9079169f26de9a547f4.jpg

Pink to redness or bleeding around the eyes, edges of the gill plates, and mouth are the next signs. Sometimes this extends down the stomach and sides of the fish. In very serious cases there might be large blood clots one out from the gills or mouth. Also notice the open mouths. Death with open mouth is a sure sign the cause was oxygen deprivation:IMG_20220403_110528980.jpg.cd8b4da855e34de180fc1c2b8121dc69.jpgIMG_20220403_110631991.jpg.0c0ea0865721485a407931fe301085ad.jpgIMG_20220403_110136408.jpg.6a795bd02a51852b052407914a382439.jpgIMG_20220403_110817139.jpg.80b3171b24ca3b3b34d04bc1a63a5256.jpg

Regions of discolorations or even necrotic ulcers on the back and sides of the fish without bleeding are also common. These sometimes look like physical damage or bruises:IMG_20220403_105810922.jpg.d094eec308310a8508aa4f7f3b30fade.jpg

These next fish are especially graphic cases. They were just beginning to recover from another infection so they were especially vulnerable to low oxygen and underwent massive hemorrhaging. The second to the most left fish was still alive when I netted it:IMG_20220403_110255937.jpg.612f5ebd09b1ce40a67b8f36578123f5.jpg

The good news is many fish can recover even from serious cases of oxygen depravation very fast when levels are brought to a more safe range.

Edited by modified lung
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