REPRODUCTION, AGE AND GROWTH OF THE BAYOU DARTER ETHEOSTOMA-RUBRUM (PISCES, PERCIDAE) - AN ENDEMIC OF BAYOU PIERRE
The life history of the bayou darter, a threatened darter endemic to Bayou Pierre, Mississippi, was studied over 18 mo during 1986-1987. Spawning, as determined by ovarian staging as well as a gonadosomatic index, occurred from April through August, with peak activity in May. Although some variation in the initiation and extent of spawning occurred between seasons, these differences were in part attributed to water temperatures. The simultaneous occurrence of females in the three reproductively active ovarian stages, and the presence of at least two distinct ova size classes, indicate that this species may spawn multiple clutches. The mean adjusted clutch size of 40 is among the lowest reported estimates for species of Nothonotus; however, assuming multiple clutch spawning, fecundity was estimated to be at least two times mean clutch size. Longevity was 3 yr, most older individuals being males, as determined from both scale analysis and length-frequency distributions. Approximately 60% of the average size of age 3 fish was achieved after the lst growing season and 80% after the 2nd. Length-frequency analyses corroborated back-calculation results based on scale data.