Inland Fisheries

7.1.2 Classification of lakes

Welch (1952) classified lakes into three types based on the nutrient status of the lake. They are namely,

1. Oligotrophic lakes

These lakes are very deep. Littoral and sub-littoral zones are narrow and less productive. Profundal zone is extensive. They are poor in nutrients. Oxygen is at high concentration in hypoliminion. Phytoplankton are low in density. These types of lakes are found in India.

2. Eutrophic lakes

These lakes are very shallow and warmer. Littoral and sub-littoral zones are abundant, sides are sloppy and bottom is sandy. They are rich in nutrients. Primary production is high due to light penetration and availability of oxygen. Phytoplankton are high in density. These types of lakes are also found in India.

3. Dystrophic lakes

These lakes have high concentration of humic acid making water unsuitable for organisms to grow. Oxygen is nearly lacking. They are rich in phosphorus, nitrogen and organic materials. However, calcium is absent. These types of lakes are also available in India.