Minimum Viable Population

Minimum viable population (MVP) is the smallest isolated population having a specified probability (usually 95%) of remaining extant for a specified time period (often 100 years), given foreseeable demographic and genetic stochasticity, environmental variability, and natural catastrophes. Below MVP, small-population effects (inbreeding depression, genetic drift, demographic accidents) accelerate extinction. MVP estimates for most vertebrate species cluster around 500–5000 individuals, but vary widely with species biology. Fish populations need high genetic effective population sizes relative to census sizes.

Small, isolated populations of fish like the Devils Hole pupfish (Cyprinodon diabolis — fewer than 200 individuals in a single cave) are considered to be below minimum viable population size.