Roanoke bass  (Ambloplites cavifrons)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The Roanoke bass, a poorly known sunfish, is the largest species in the genus Ambloplites (3). Often confused with the similar, and more widely ranging, rock bass (Ambloplites rupestris), the Roanoke bass has a large, robust and somewhat compressed body, which is predominantly olive green, brown or tan, fading to grey and cream on the underside (4). It is distinguished from closely related species by the finer scales on the sides and the naked or incompletely scaled cheeks, and the presence of numerous iridescent gold to white spots on the upper body and head of the adult. With bright red eyes, the Roanoke bass is also often referred to as the “red eye” (3).

The Roanoke bass occurs in the United States where it has one of the smallest ranges of native game fishes (4). It is endemic only to the Chowan, Roanoke, Tar and Neuse river drainages of Virginia and North Carolina (5). Historically, intentional stocking for sportfishing has occurred throughout these drainages; however, such efforts to increase populations of Roanoke bass have generally failed (6) (7).

The Roanoke bass occurs in medium to large streams with firm substrate, high levels of dissolved oxygen, and a near neutral pH (8) (9). It rarely occurs in lakes, instead preferring well-flowing parts of pools, areas of moderate to swift currents, and the deeper water around the shelter of large boulders or tree roots (3).

The reproductive biology of the Roanoke bass is largely unknown, but is considered to be similar to that of the rock bass. During the spawning season, from mid-May to mid-June, the male builds a nest in unvegetated shallows over gravel substrates and guards it from intruders (10). Maturity occurs at approximately two years old, typically when the Roanoke bass has reached a total body length of 15 centimetres and a body weight of 75 grams (9). Populations appear to be dominated by large juveniles and adults, suggesting that reproductive rates, and/or survival rates of young juveniles, within this species may be low (3) (8) (9).

As with other species in the Centrarchid family, the Roanoke bass is a carnivorous fish, preying on small aquatic invertebrates when young and consuming an increasing amount of crayfish as it matures (9).

Throughout many parts of its range, the Roanoke bass occurs alongside the morphologically similar rock bass. Although each species has slightly different habitat requirements, the rock bass is considered a better competitor for prime habitat. These two species are also known to hybridise (2).

The range of the Roanoke bass has receded and it is now nearly extirpated from parts of the Roanoke River where it was once widespread (11). The decline of this species has been brought about by the adverse effects of substantial habitat alterations such as siltation, impoundment construction and the creation of large reservoirs, compounded by the impact of wide-scale introductions of rock bass, with which the Roanoke bass competes and hybridises (2). Furthermore, parts of the Roanoke River have experienced chronic pollution, at times causing major fish kills (12) (13).

The rarity of the Roanoke bass throughout its native range has led to the states of North Carolina and Virginia listing this sunfish as a Species of Special Concern (7). The North Carolina Wildlife Resources Commission has proposed changes in fishing regulations for 2011, imposing stricter limits on the number of fish caught each day and a minimum catch size. The implementation of these measures should hopefully help protect the Roanoke bass from overharvesting (14).

View information on this species at the UNEP World Conservation Monitoring Centre.