Definitions for "Natural mortality"
Deaths in a fish stock caused by predation, pollution, senility, etc., but not fishing.
A technical term which refers to the proportion of the fish population dying by any causes other than fishing. As with fishing mortality, can be translated into a yearly natural mortality rate expressed as a percentage, using a mathematical formula. See also Fishing mortality.
deaths of fish from all causes except fishing. It is often expressed as a rate that indicates the percentage of fish dying in a year; for example, a natural mortality rate of 0.2 implies that e-0.2 of the population—about 22%—will die in a year from causes other than fishing.
Keywords:  decrease, net, increase
Net Increase (or Decrease)