Question

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

Answer 1

Hint: Sometimes it is noted that aquatic life starts dying in mass numbers which is an alarming signal for environmental protection as there can be serious issues behind mass mortality. Mortality of fishes in mass numbers in captivated settings can impact pisciculture industries seriously and can lead to major economic loss. The reason behind this can be many which impact the survival of fishes.

Complete answer:
There can be a variety of reasons for the mass mortality of fishes in a pond. Some of these reasons are listed below:
1. Temperature fluctuations: Sometimes due to temperature fluctuations the fishes can’t acclimatize and die of increased or decreased temperature. Fishes living in colder water can’t survive in warmer tropical waters.
2. Eutrophication and algal blooms: Pollution may lead to development of algal blooms in ponds which lead to decrease in dissolved oxygen of the pond which cause mass fish mortality. Also, certain algal blooms also produce toxins which cause the death of fishes.
Drainage of poisonous compounds in ponds – Drainage of poisonous compounds in ponds like mercury can impact survival of aquatic life and can lead to mass fish mortality.
3. Spread of disease: Spread of certain diseases in fish populations in ponds can bring out their deaths in mass number. Example- Cotton mouth disease.
Gill blockage in fishes due to some pollutants – Excessive organic pollutants in ponds can promote algal growth on fish gills which blocks them and can be a reason behind mass fish mortality.
Decrease in DO – Increased organic pollution means the dissolved oxygen of the pond is reduced and mass fish mortality occurs in such hypoxic conditions.

Note:
Low oxygen levels in the water are the most common cause of mass fish fatalities. However, fish fatalities can occur for a variety of reasons. Even when low oxygen levels are the source, the reason for the low oxygen levels cannot always be determined, and additional stressors may exist. Inability of fishes to adjust with changing ecological parameters can also be a major reason behind fish fatalities.