Bivalve effects on the food web supporting delta smelt - A long-term study of bivalve recruitment, biomass, and grazing rate patterns with varying freshwater outflow

10 mm at D7 in the wet years. 

The largest mean sized Corbicula were in the southern Delta (C9 ≈25 mm during 1996–97 and 2012–2013), and the smallest average sizes were in the San Joaquin River (P8 and D16). Corbicula at the upstream Sacramento River station (D24) and in the southern Delta (C9) showed similar interannual patterns in average size although the animals at C9 were consistently larger than those at D24 were. Corbicula in Franks Tract (D19) and the Old River (D28A) south of Franks Tract were also similar in size and in interannual patterns. 

At the few stations where Potamocorbula and Corbicula co-occur, it appears that they did not hinder each other’s growth. Both bivalves had large animals at D4, where Corbicula size increased coincident with the presence of Potamocorbula in 1987. Corbicula were observed in wet years prior to Potamocorbula’sinvasion at D7 (Grizzly Bay) and were capable of growing to significant size in wet years (> 20 mm in 1986).