LIFE-HISTORY OF THE ENDANGERED JAMES SPINYMUSSEL PLEUROBEMA-COLLINA (CONRAD, 1837) (MOLLUSCA, UNIONIDAE)

The reproductive period, host fish requirements, and population charac teristics of the James spinymussel [Pleurobema collina (Conrad, 1837)] were studied from 1987 to 1989 in the James River drainage, West Virg inia and Virginia. This summer brooder was gravid from late May throug h early August and released the majority of glochidia in early June th rough late July. The mean fecundity was roughly 13,000 brooded eggs/fe male. Observations in the field and laboratory implicated fishes of th e Cyprinidae as hosts for glochidia of the James spinymussel. Induced infestations of glochidia on fishes in the laboratory confirmed seven host species: the bluehead chub [Nocomis leptocephalus (Girard)], rosy side dace (Clinostomus funduloides Girard), satinfin shiner [Cyprinell a analostana (Girard)], rosefin shiner [Lythrurus ardens (Cope)], cent ral stoneroller [Campostoma anomalum (Rafinesque)], blacknose dace [Rh inichthys atratulus (Hermann)], and mountain redbelly dace [Phoxinus o reas (Cope)]. The age class structure of two populations, obtained by thin-sectioning valves collected in muskrat middens, ranged from 3 to 19 yrs with evidence of strong and weak year classes. Incidence of spi nes differed significantly among populations. The mean annual mortalit y rate of adults was 15.6 +/- 1.4%.