Life history and propagation of the endangered dromedary pearlymussel (Dromus dromas) (Bivalvia:Unionidae)

The reproduction, demography, and propagation of the endangered dromedary pearlymussel (Dromus dromas) (Lea, 1834) were studied in the Clinch and Powell rivers, Tennessee. Viable populations of the dromedary pearlymussel now occur only in the Clinch and Powell rivers; the species has been extirpated from the remaining portions of its range in the Cumberland and Tennessee river drainages. Females are long-term winter brooders, and they are gravid from October to June. Glochidia are contained in conglutinates that are red to white and resemble freshwater leeches or flatworms. Conglutinates are 20 to 40 mm long and are released through the excurrent aperture. Estimates of fecundity based on 7 gravid females collected from the Clinch River were 55,110 to 253,050 glochidia/mussel. The ages of 66 valves of D. dromas were determined by thin-sectioning and ranged from 3 to 25 y. Annual growth averaged 5 mm/y until age 10 and decreased to ???1.2 mm/ y thereafter. Nineteen fish species were tested for suitability as hosts for glochidia. Ten were confirmed as hosts through induced infestations of glochidia: black sculpin (Cottus baileyi), greenside darter (Etheostoma blennioides), fantail darter (Etheostoma flabellare), snubnose darter (Etheostoma simoterum), tangerine darter (Percina aurantiaca), blotchside logperch (Percina burtoni), logperch (Percina caprodes), channel darter (Percina copelandi), gilt darter (Percina evides), and Roanoke darter (Percina roanoka). Juveniles produced from these hosts were cultured in dishes held in nonrecirculating aquaculture systems containing fine sediment (<105 ??m) and were fed the green alga Nannochloropsis oculata every 2 d. Survival of 2810 newly metamorphosed juveniles was 836 (29.7%) after 1 to 2 wk.