What could be responsible for sudden high mortality on my fish farm?

Few weeks ago, I got troubling call from one of our esteemed customers, he seems to be having a hard time at the other side of the line. I have to reassure him things will be ok, that he should be calm and explain what is happening at his farm to me.

He said, "My fish died massively, I have counted more than 700 today". It broke my heart. I started probing immediately in order to get to the bottom of the issue. These particular fish were stocked over a month before the incident, very heathy and the mortality recorded prior to that time were due to cannibalism and competition.

Before I even go further, Let me quickly explain Fish Mortality; it's a parameter used in fish farming to account for the loss of fish in a stock through death. Death in the fish population can happen in two forms, namely: natural mortality and fishing mortality.

Natural mortality is when fish removed from the pond is not through harvesting or fishing but died through disease, contamination, cannibalism, competition, and predation.

We also have fishing mortality, which is when fish is being removed due to fishing activity. Like harvesting with the aid of fishing gear.

Back to my friend who called... I started asking him when they all started dying, and he said overnight.

When last did you feed them?. He said last night.

Were aggressive toward the feed?. He said yes.

I even asked if their belly is red, swollen, and body piling. He answered no.

Their water source is from a table water production plant. Water from the factory is said to be channeled to all ponds and it's ever-flowing. What if they used chlorine and other disinfectants that are harmful to fish at the factory?

He said other fish on the farm are okay, so I zero that out too. I told him the way the fish died looked like some pollutant find their way into the pond.

I recounted my experience with herbicide. On this particular day another friend uses plastic tanks for rearing fish. His neighbour use the herbicide two housed away from where the plastic ponds were, on the second his fish started dying.

It was later discovered that air blown a black nylon into the fish tanks causing high mortality.

And it clicked... He said they fumigated the farm. fumigated the farm. And the case was closed.

And we do know that there could be other causes responsible fish dying in a farm; they ranges from diseases to water pH or water hardness issue. It's usually a prolong and untreated bacterial problem like Ichthyophthirius multifiliis infection and the like that can result in many dead if not treated fast.

Feed inducted mortality is also common due to over feeding, contaminated feed, aflatoxin and deficiency in feed ingredient.

When water pH is very low and the water on the fish is changed completely by continuous water flow through or drain and fill system. Fish mortality could be high especially if they are not yet acclimatized to the water and environment.

In conclusion, There are many causes of fish mortality but when it comes to sudden mass death in the farm let us think of pollutant or aflatoxin, could be in feed or from water sources.

Your questions and feedback will be highly appreciated.

https://m.facebook.com/story.php?story_fbid=pfbid0166gs7B8bWvBUX4cWp8EehR1ie25ftYdV838H5329iKxVanasychcWwR1iEkNgYjl&id=269983423184954

Please don't forget to like and share.