Juvenile gizzard shad abundance increases with reservoir productivity (Bremigan
and Stein 1999), and swamps and estuaries like the Barataria Estuary are some of the
most productive areas in the world (Miller 2001). In highly eutrophic (nutrient-rich)
ecosystems, gizzard shad often attain the highest biomass relative to other fish in the ecosystem (Miranda 1983; Bachmann et al. 1996). DiCenzo et al. (1996) found gizzard
shad to have an 80-86% higher relative abundance in eutrophic Alabama reservoirs tha
in comparable oligotrophic (nutrient-limited) reservoirs. Clayton and Maceina (2002),
when comparing two Tennessee River impoundments, observed a higher abundance of
gizzard shad in the reservoir with higher chlorophyll-a concentrations, which corresponds
to higher primary production. As the Barataria Estuary is highly productive, it is not
surprising that gizzard shad were by far the most abundant species
n
collected during this
study. their
ord
f
size
r
The fact that their abundance levels in Bayou Chevreuil were greatest during
spawning period is typical of gizzard shad (Noble 1981; Fontenot et al. 2001; Rutherf
et al. 2001; Bonvillain 2006).