Herring is good bait? Fishfinder help!

[sabiki]

I fish in the potamac river(DC/VA). I use herring as live and cut bait for Stripers. Lately Ive been having some trouble catching herring. (maybe because the water is kinda muddy from last weeks rain)
Last year at this time I was catching 5-6 herring every cast (on a 6 hook sabiki jig).

Can anyone answer these questions?

1. Does anyone know where herrings like to stay?(in general)

2. What attracts herring?

3. Will a bigger piece of cutbait catch a bigger rockfish?

4. Will a fishfinder be usefull for finding herring and stripers?



Thanks!