Digging a little deeper into the science I found this note, in a report to the VMRC by Drs Nathan Smith and Cynthia Jones, regarding isotope values in Menhaden.
" Previous studies of menhaden diet based on stomach contents indicated phytoplanktivory, but while they may consume phytoplankton, zooplankton may be much more important than previously reported"
Seems to me I must have read a previous study.
Ahh, more nebulosity.
I will get my shovel and dig some more.
