1st record: CA/Suisun Marsh (1981-2005, Schroeter 2008). This species may have been observed in the Sacramento-San Joaquin Delta, as early as 1959, based on field notes from California Fish and Game and U.S. Fish and Wildlife Service (Rees and Gershwin 2000). Analysis of plankton survey records indicates a trend of increasing abundance from 1981 to 2005 (Schroeter 2008).
Petaluma/CA/Petaluma River (San Francisco Bay) (1992, Mills and Sommer 1995); CA/Napa River (San Francisco Bay) (1998, Rees and Gershwin 2000); CA/Suisun Marsh (1981-2005, Schroeter 2008; 2004-2005, Baumsteiger et al. 2018, 0.1-2.5 m-3, 2.3-9.1 PSU); Suisun City/CA/Suisun Slough (San Francisco Bay) (1997, Rees and Gershwin 2000); CA/Sacramento-San Joaquin Delta (Mills and Rees 2000); Chipps Island/CA/Suisun Bay (McLaughlin 2003, http://www.iep.ca.gov/report/newsletter/2003fall/IEPNewsletter_fall2003_mar23.pdf)
|Potentially, M. marginata sp. is a competitor with larval fishes, particularly economically important Striped Bass (Morone saxatilis) and endangered Delta Smelt (Hypomesus transpacificus) (Schroeter 2008; Wintzer et al. 2011b; Wintzer et al. 2011c). Temporal and dietary overlap was greatest with Delta Smelt, and introduced Threadfin Shad (Dorosoma petenense), but minimal with Morone saxatilis and threatened Longfin Smelt (Spirinchus thaleichthys) (Wintzer et al. 2011c).|