Fecundity and the Dynamics of Multiple Spawning in Darters: An In-Stream Study of Etheostoma rafinesquei

Abstract

We determined the annual fecundity and spawning periodicity of the Kentucky snubnose darter, Etheostoma rafinesquei, by collecting all ova spawned by individual females during 26-42 d of in-stream confinement. Fecundity estimates based on spawned ova were comparable with those based on counts of mature follicles in wild-caught females. Each of 15 females, captive for 12 or more days, spawned multiple clutches. Spawning of multiple clutches was related to group synchronous cycles of oocyte development. Vitellogenic follicles were recruited from nonvitellogenic oocytes during the spawning season. Batch fecundity estimates of wild-caught females were not equivalent to daily spawns of caged females. Spawning on successive days was observed frequently; spawning of a batch (clutch) of ova was protracted. Batch fecundity was directly correlated with stream temperature at temperatures below 21.5 C but not related to temperature at temperatures exceeding 21.5 C. Spawning was negatively influenced by high discharge and by stream temperatures in excess of ca 21.5 C, the apparent thermal maximum. Females of the Kentucky snubnose darter spawned ca 500-1000 ova during the 1988 spawning season.