Host Fishes and Life History of the Round Hickorynut (Obovaria Subrotunda)

Abstract

The Round Hickorynut, Obovaria subrotunda, is declining throughout its range, but little life history information exists for the species. We examined host use and glochidial size in Buck Creek (Cumberland River drainage) and the Licking River (Ohio River drainage), Kentucky, and we examined age and growth in Buck Creek. Glochidia of O. subrotunda from Buck Creek metamorphosed on five darter species (Percidae)—Etheostoma baileyi, Etheostoma blennioides, Etheostoma gore, Etheostoma variatum, and Percina stictogaster—but not on 43 other fish species from nine families; host use was broadly similar to previous studies in the Duck River, Tennessee, and Lake St. Clair, Ontario. Glochidia from the Licking River metamorphosed only on Eastern Sand Darters (Ammocrypta pellucida) and not on 11 other darter species, including two that produced juveniles in the Buck Creek trial. Glochidial metamorphosis was higher on A. pellucida than on any other species, suggesting that sand darters are primary hosts for O. subrotunda, but sand darters do not occur in several streams occupied by O. subrotunda. Such major differences in host use may indicate phylogenetic divergence between these populations. Glochidial size differed significantly between the Buck Creek and Licking River populations, suggesting that it may have taxonomic value also. Obovaria subrotunda was relatively short-lived (13 yr) and fast-growing (K = 0.22), and age-at-maturity was estimated at 2–3 yr. Males and females had similar growth rates, but males were substantially larger (L∞: males = 53.7 mm; females = 39.2 mm). Life-history data support categorizing O. subrotunda as a periodic life-history strategist, and this view provides benchmarks for assessing population health and responses to watershed conditions.