A semelparous organism is one that reproduces only once in its life history. Because such an individual's fitness depends entirely on that reproductive effort, the best strategy is –– all things being equal –– to invest as much energy and resources as possible. The salmon is often used as an example of a semelparous species. Semelparity may reflect an optimal strategy under conditions that leave a very small chance of reproducing more than once (e.g. high rate of adult mortality, limited resources).
See also iteroparous.