Size, Age and Demography of Metamorphosis and Sexual Maturation in Fishes

Understanding what determines the timing of transitions betweenlife-history stages in fishes is crucial to an understandingof their demography. Most theoretical treatments assume thatthese transitions are age dependent, but evidence accumulatingfrom a variety of organisms indicates that size is an importantvariable also. In the starry flounder, Platichthys slellatus(Pallas),the onset of metamorphosis is more closely related to size thanage. In the platyfish, Xiphophorus maculatus (Günther),the onset of sexual maturation depends on both size and age.I compare these results with those reported for other organisms,and outline the expected ecological correlates of age- and sizedependenttransitions between life history stages in general.