instantaneous rate of natural mortality (when natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multiplied by the ratio of natural deaths to all deaths (Ricker, 1975). Also called force of natural mortality)1) annual mortality rate (the ratio between the number of fish which die during a year from causes other than fishing and the number alive at the beginning of that year. Also called annual natural mortality rate, conditional natural mortality rate, seasonal natural mortality rate). Also abbreviated as n2) conditional fishing mortality rate (the fraction of an initial stock which would be caught during the year (or season) if no other causes of mortality operated (Ricker, 1975). Also called annual or seasonal fishing mortality rate)3) metre (1.094 yd)
Dictionary of ichthyology. 2009.