Reasons For High Mortality Rate In Fishes

The population of the world is swiftly strengthening every single day, and the demand for food also increased. Fish farming is a profitable business as it can contribute a lot to the growing population, however,  fish farmers are distressed about the high mortality rate in aquaculture and are in search of a solid solution. There are various reasons which lead to a huge loss in the aquaculture industry and some causes are listed below:

Spread of disease

Aquaculture is a closed system of farming where fishes are bred at high density in close vicinity. The higher density of fish results in a high contact ratio and transference rate leads to death and epidemics. Diseases are less often in wild fisheries as it is scantly populated. Pathogens are ever-present in Aquaculture, but not always at an adequate level to produce infections. Another cause of the disease is the increase in the stress level of fishes through low oxygen levels, poor water quality, temperature variations, salinity fluctuation. Fishes are extremely sensitive towards environmental changes and these changes result in weaker immunity, eventually makes fishes more vulnerable to diseases.

LODOS (Low dissolved oxygen syndromes)

The fish mortality is highly influenced by the availability of oxygen and the concentration of dissolved oxygen in large scale integrated fish farming. Low dissolved oxygen syndrome is the most crucial aspect in high-density fish farming and it is too complicated to understand, foretell, and manage. It is important to check the oxygen level frequently and adequate aeration should be provided. If the culture water contains algae and phytoplanktons, they utilize more oxygen during night time and leads to the death of fishes.

Variation in water temperature

Temperature is yet another most significant factor affecting the growth and survival of all organisms. Water temperature plays a vital role in aquaculture but it cannot be controlled as it depends on solar radiation, air temperature, and the temperature of the water circulating through the culture system. At a particular temperature, the growth of fish increases rapidly with the increasing temperature until the optimum temperature reaches. As the temperature rises over the optimum temperature, the growth will slow, stops and finally fish will die by the high temperature. 

The cold water fishes won’t endure the temperatures beyond 20-25 degrees Celcius where warm water fishes can survive at lower winter temperatures. Usually, warm water fishes will not reproduce below 20 degrees Celcius or grow below 10-15 degrees Celcius but it can survive at very low temperatures.In the case of tropical fishes, they can’t survive at a temperature below 10-20 degrees, and most never grow below 25 degrees Celcius.

Poor water quality

The quality of water is essential in fish farming because poor quality can cause the death of fishes. Water quality includes temperature, ph, dissolved oxygen content, ammonia, and salinity. The level of salinity will not be the same for all fishes. The culture water must be more saline for culturing seawater fish than the freshwater species. The Ph and oxygen level gets altered by the presence of biotoxins, pesticides, etc. All these factors should be in a normal condition for the survival of aquatic fishes.


The mortality of fish is a threat to the industry aquaculture as it causes extreme financial losses. So, the mortality rate must be reduced for gaining high productivity and profits. The culture units of aquaculture should possess frequent supervision, confirming all factors are favorable for the survival of fishes. If the production of fishes is undertaken with less care, no profit can be earned and even the invested money for the production cant be returned. If it is properly managed, aquaculture can be a great beneficial business.


 The Impact of High-Density Fish Farming on the Fish Mortality Rates. Retrieved from  on September 23rd, 2020

What is a fish disease? Retrieved from,it%20more%20susceptible%20to%20disease.&text=In%20developing%20countries%2C%20neighboring%20farms,spread%20of%20disease%20explains%20Mohan.  on September 23rd, 2020

Water temperature in aquaculture. . Retrieved from  on September 23rd, 2020

Effect of Different Salinity Level within Water Against Growth Rate, Survival Rate (FCR) of Catfish (Clarias sp.). Retrieved from  on September 23rd, 2020

Leave a Comment