Threatened Fishes of the World: Etheostoma sellare (Radcliffe & Welsh) 1913 (Percidae)

Abstract

Common name: Maryland darter. Conservation status: Federally endangered (U.S. Fish & Wildlife Service 1967), critical habitat designated 29 August 1984 (U.S. Fish & Wildlife Service 1984). Also considered endangered by the State of Maryland. Identification: Diagnosed from all other darters by an asymmetrical caudal fin base and broad head, and from members of the subgenus Etheostoma by a short flattened genital papilla in females and narrowly connected branchiostegal membranes (Page 1983). No other darter on the middle Atlantic Slope has four dark, forwardly directed, oblique saddles across the back and incomplete dark bars of pigment on the lower half of the body below the lateral line (Knapp 1976). Maximum length 70 mm SL. Distribution: Known only from three sites in the vicinity of the Fall Line, at head of Chesapeake Bay. Described from a single specimen taken in Swan Creek in 1911. In 1965 E. sellare was also found in Swan Creek and its largest tributary, Gasheys Run. All recent records (post 1965) are from the lower-most riffle on Deer Creek, immediately above its confluence with the Susquehanna River in Harford County, Maryland. Prior to impoundment by Conowingo Reservoir in 1928, the mainstem Susquehanna River in this area was characterized by rocky shoals and ledges, with many shallow raceways and runs, which likely would have provided optimal habitat for E. sellare. Abundance: During 1965, 110 specimens were taken from the Deer Creek population. This species has not been found in such numbers since, and no specimens have been observed since 1989, despite extensive recent survey efforts (Raesly, pers. comm. and Maryland Biological Stream Survey). Habitat and ecology: The riffle on Deer Creek that supported the largest known population ranges from 12 to 25 m wide, with rubble near the head of the riffle and increasing amounts of silt and gravel toward the sides and foot. Rooted aquatic plants, mostly Podostemum ceratophyllum, are seasonally abundant. Swan Creek and Gasheys Run are much smaller streams with a limited amount of suitable habitat. Swan Creek is now severely degraded with extensive silt deposits. Diet of 35 individuals taken on 10 November 1965 included large numbers of snails (Knapp 1976). The only other darter taxa known to consume snails in quantity are the members of the Percina subgenus Imostoma. The broad head and wide gape of E. sellare may facilitate ingestion of snails. Reproduction: Spawning is believed to occur in late April or early May (Knapp 1976). Females develop a swollen white pad on the urogenital papilla, while the male papilla is short and shows little seasonal variation. Nuptial tubercles are not developed. Threats: Urban/suburban development related to proximity to the Baltimore–Philadelphia metropolitan complex, with associated changes in sediment and nutrient loading, flow and thermal regimes. Observed declines during the 1980s were correlated with increased sediment deposition (Raesly, pers. comm.). Impoundment of Conowingo Reservoir (and subsequent manipulation of flows downstream) reduced potential habitat in the mainstem Susquehanna. Introduced populations of E. blennioides and E. zonale have recently expanded in the lower Susquehanna drainage, and may compete with E. sellare for resources. Conservation action: Maryland DNR and the U.S. Fish & Wildlife Service have implemented a recovery plan (U.S. Fish & Wildlife Service 1985) with goals of managing streamside buffer zones to reduce sedimentation and agricultural pollution, maintenance and improvement of water quality. Intensive surveys of the basin have not documented specimens since 1988. The last remaining habitat that has not been thoroughly surveyed is the mainstem Susquehanna River below Conowingo Reservoir. The extreme flow fluctuations produced by Conowingo Reservoir make this habitat difficult to sample effectively. Survey work in the mainstem should be a top priority. Recent efforts to delist the darter are ill-founded without additional survey work.