Physical & Chemical Features: Their Influences on Water Bodies
Environment is the sum total of physical, chemical and biological factors influencing the responses of
the organisms. The inter-relationship between the fish & the environment is extremely complicated, multi-
lateral & very vast. Fishes are totally dependent on their abiotic (physical & chemical) factors as they
directly influence their physiological processes, habitat suitability, and overall ecosystem dynamics.
Changes in any of these factors can lead to significant impacts on fish populations, including shifts in
community structure, reduced growth rates, or even local extinctions. Understanding these dependencies
is essential for effective fisheries management and conservation efforts.
The abiotic factors include –
Abiotic Factors
Physical Factors Chemical Factors
1. Temperature 1. Dissolved Oxygen (DO)
2. Pressure 2. Dissolved CO2
3. Density 3. Salinity
4. Turbidity 4. pH
5. Light 5. Ammonia
6. Colour
7. Buoyancy
8. Depth
9. Mobility
10. Surface Tension
11.Movement of water
, A. Physical Factors
Physical factors, also known as abiotic factors, refer to the non-living components of an environment
that influence the growth, development, and survival of organisms within biological communities. The
influence of physical factors on water bodies is a central theme in limnology, the study of freshwater
ecosystems. These factors significantly affect the physical, chemical, and biological characteristics of
aquatic environments, ultimately determining their health and ecological balance. Such factors are
described below –
1. Temperature
Temperature is one of the most important factors in an aquatic environment. In fact, no other single
factor may have so many profound influences and so many direct & indirect effects like other
Poikilotherms. Fishes are more dependent on the temperature of their surrounding environment.
Diurnal and seasonal variations are very much more common in freshwater environments than in the
marine environment. A diurnal variation range of 4.8 - 5°C has been recorded in a tropical pond with an
average depth of three meters. In shallow waters within an average depth of 1.5m, the lowest night
temperature is 26.6°C.
Changes in the metabolic rate of fish are most probably connected with the changes in the surrounding
environmental temperature. The temperature functions as the signalling factor of spawning and migration.
Fishes can live at very different temperatures, for example, the desert pupfish (Cyprinodon macularius)
can survive over 52°C whereas Boreogadus saida, known as the polar cod or as the Arctic cod, can survive
at -2°C temperature. The digestion and consumption of food in some fishes also rise with temperature,
e.g., the bluegill (Lepomis macrochirus) may consume average weekly rations up to 35% of the body
weight in the summer at 20°C and less than 1% during winter at 2 – 3°C.
Temperature plays a crucial role in influencing fish migration patterns. For example, salmon migrate
upstream to freshwater rivers to spawn in cooler waters, while some tropical fish species migrate to deeper
waters during the warmer months to escape high temperatures near the surface. Temperature changes can
also trigger hormonal responses in fish, prompting them to migrate to specific locations at particular times
of the year.
The rate of development of fish is also related to a significant extent to changes in temperature. The
temperature has also an effect on the length of the hatching period. For example, Temperature significantly
influences the hatching period of rainbow trout (Salmo gairdneri) eggs. Warmer temperatures generally
lead to shorter incubation periods, while colder temperatures result in longer hatching times. The optimal
temperature range for rainbow trout egg development is between 7°C and 12°C. The following shows how
rise in temperature gradually shorten hatching period –
Temperature (°C) Hatching period to the nearest day
5.7 14
8.2 8
12.9 6
17.6 3
Environment is the sum total of physical, chemical and biological factors influencing the responses of
the organisms. The inter-relationship between the fish & the environment is extremely complicated, multi-
lateral & very vast. Fishes are totally dependent on their abiotic (physical & chemical) factors as they
directly influence their physiological processes, habitat suitability, and overall ecosystem dynamics.
Changes in any of these factors can lead to significant impacts on fish populations, including shifts in
community structure, reduced growth rates, or even local extinctions. Understanding these dependencies
is essential for effective fisheries management and conservation efforts.
The abiotic factors include –
Abiotic Factors
Physical Factors Chemical Factors
1. Temperature 1. Dissolved Oxygen (DO)
2. Pressure 2. Dissolved CO2
3. Density 3. Salinity
4. Turbidity 4. pH
5. Light 5. Ammonia
6. Colour
7. Buoyancy
8. Depth
9. Mobility
10. Surface Tension
11.Movement of water
, A. Physical Factors
Physical factors, also known as abiotic factors, refer to the non-living components of an environment
that influence the growth, development, and survival of organisms within biological communities. The
influence of physical factors on water bodies is a central theme in limnology, the study of freshwater
ecosystems. These factors significantly affect the physical, chemical, and biological characteristics of
aquatic environments, ultimately determining their health and ecological balance. Such factors are
described below –
1. Temperature
Temperature is one of the most important factors in an aquatic environment. In fact, no other single
factor may have so many profound influences and so many direct & indirect effects like other
Poikilotherms. Fishes are more dependent on the temperature of their surrounding environment.
Diurnal and seasonal variations are very much more common in freshwater environments than in the
marine environment. A diurnal variation range of 4.8 - 5°C has been recorded in a tropical pond with an
average depth of three meters. In shallow waters within an average depth of 1.5m, the lowest night
temperature is 26.6°C.
Changes in the metabolic rate of fish are most probably connected with the changes in the surrounding
environmental temperature. The temperature functions as the signalling factor of spawning and migration.
Fishes can live at very different temperatures, for example, the desert pupfish (Cyprinodon macularius)
can survive over 52°C whereas Boreogadus saida, known as the polar cod or as the Arctic cod, can survive
at -2°C temperature. The digestion and consumption of food in some fishes also rise with temperature,
e.g., the bluegill (Lepomis macrochirus) may consume average weekly rations up to 35% of the body
weight in the summer at 20°C and less than 1% during winter at 2 – 3°C.
Temperature plays a crucial role in influencing fish migration patterns. For example, salmon migrate
upstream to freshwater rivers to spawn in cooler waters, while some tropical fish species migrate to deeper
waters during the warmer months to escape high temperatures near the surface. Temperature changes can
also trigger hormonal responses in fish, prompting them to migrate to specific locations at particular times
of the year.
The rate of development of fish is also related to a significant extent to changes in temperature. The
temperature has also an effect on the length of the hatching period. For example, Temperature significantly
influences the hatching period of rainbow trout (Salmo gairdneri) eggs. Warmer temperatures generally
lead to shorter incubation periods, while colder temperatures result in longer hatching times. The optimal
temperature range for rainbow trout egg development is between 7°C and 12°C. The following shows how
rise in temperature gradually shorten hatching period –
Temperature (°C) Hatching period to the nearest day
5.7 14
8.2 8
12.9 6
17.6 3
