Morphoedaphic Index (MEI) - the ratio of salinity to average lake depth. According to a number of researchers, fish production is significantly related to MEI. It is used in studies to determine ichthyomass and the size of fish catches.

For example, the Morphoedaphic Index (MEI) calculates the concentration of phosphorus in water that is characteristic of natural processes in a waterbody, as well as the proportion of phosphorus contributed by all anthropogenic activities.

The formula used to calculate MEI is:

MEI = C/N,

where MEI is the morphoedaphic index;

C is the average conductivity of water,

μs/cm at 20 ºC;

H is the average depth of the water body, m.