The Effect of Torrential Rains on the Reproductive Cycle of Rhinichthys osculus in the Chiricahua Mountains, Arizona

Abstract

The reproductive cycle of the speckled dace, Rhinichthys osculus (Girard), in the Chiricahua Mountains, Arizona, is bimodal, with discrete peaks in early spring and late summer, if the precipitation is normal. In periods of drought, overcrowded, undernourished populations fail to reproduce, and reproduction is otherwise thinly scattered in the spring and lacking in late summer. Rising temperature, increasing daylength, and perhaps flowing water are essential and adequate stimuli for spring reproduction but decreasing daylength, declining temperatures, and flowing water are inadequate stimuli for late-summer reproduction. Reproduction is greatest in the spring with streams swollen from melting snow, and in late summer following freshets or flash floods. A single flood in late summer induces spawning; a single flood in early summer does not. Basically, the reproductive period seems to be regulated by the photoperiod.