The Life History and Distribution of the Roanoke Bass Ambloplites cavifrons Cope, in Virginia

Abstract

The life history and Virginia distribution of the Roanoke bass Ambloplites cavifrons Cope was studied from January 1979 through January 1980. Populations in the Roanoke and Chowan drainages were disjunct and locally uncommon, possibly owing to the patchiness of suitable physical habitat. Growth of male and female Roanoke bass was similar and significantly greater (P < 0.05) when compared with northern rock bass Ambloplites rupestris and redbreast sunfish Lepomix auritus. Ponderal indices were similar for both sexes and age dependent. Young A. cavifrons consumed small aquatic invertebrates; juveniles included crayfish and fish in the diet; adults ate predominantly crayfish. Seasonal diet variation was greater among juveniles than adults. Maturity occurred at age II if 150 mm TL and 75 g body weight had been attained. The reproductive season extended from May through June as water temperatures approached 20C. Fecundity estimates exhibited a linear relationship to length and weight. Evidence of widespread year-class failure in 1978 and 1979 was attributed to adverse spring stream conditions. Ecological and environmental impacts have caused a recent decline in Roanoke bass abundance, warranting the species the conservation status of Special Concern. INTRODUCTION The Roanoke bass Ambloplites cavifrons Cope has long remained one of the most poorly understood centrarchid fishes. Because of its relatively small geographic range and controversial taxonomic status, A. cavifrons has been generally unrecognized as a potential game fish and has received little attention as a diminishing species. The species was discovered in the upper Roanoke drainage, Virginia, in 1867 by E. D. Cope (1868), and was long thought to be restricted thereto. Specimens collected during the late 1800s from the Virginia portion of the Chowan drainage were documented only recently (Cashner and Jenkins, 1982). Early taxonomists questioned the specific distinctiveness of the cavifrons form from the more widespread northern rock bass Ambloplites rupestris (Rafinesque), its closest geographic congener. Following the discovery of A. cavifrons in North Carolina in 1963, where it is now known to occupy the Tar and Neuse drainages, the two species were clearly distinguished (Smith, 1968). The extensive treatment of the systematics and distribution of the species by Cashner and Jenkins (1982) has further clarified the taxonomic status of A. cavifrons. In Virginia, the distribution of Ambloplites cavifrons has been reduced by impoundment, pollution, siltation and competition with introduced populations of A. rupestris in the upper Roanoke drainage (Cashner and Jenkins, 1982). The limited native range and increasing environmental pressure, combined with a need for a more complete understanding of the biology of the species, has warranted for A. cavifrons the conservation status of Special Concern (Deacon et al., 1979). Prior to this study, the life history and distribution of the Roanoke bass within North Carolina has received considerable study (Smith, 1970, 1971). However, early 1 Current address: Environmental Resources Management, Inc. 999 West Chester Pike, P.O. Box 357, West Chester, Pa. 19380.