There is mass mortality of fishes in a pond. What may be the reasons?

There is a mass mortality of fishes in a pond. What may be the reasons?

There is a mass mortality of fish in a pond. What may be the reason?

What is mortality?

What is mortality rate?

At the sweage discharge point of river, high mortality of fishes occured. Choose the most correct reason for this :-

A lake near a village suffered heavy mortality of fishes within a few day. Consider the following reasons for this?