Life cycle and population dynamics of the Asian clam Corbicula fluminea (Bivalvia: Corbiculidae) in the Saone River at Lyon (France)

The Corbicula of the Saone at Lyon were sampled every month from September 1996 to December 1999. These populations are characterised by a single annual reproduction period starting in May or June and ending in September or October in which two peaks of intensity can be distinguished; the presence of one or more cohorts according to year; low growth in spite of a growth period that generally lasts from March to October; and a lifespan of about 5 years. Although the effect of toxic substances can be considered, it appears that the reason for the low recruitment levels observed from 1997 to 1999 are above all due to the small quantities of food available, especially chlorophyll a.