How can you tell if your fishing on a shell bed? I read you can feel them. I guess that would be possible on a soft or sandy bottom. Are there certain ares that are more conducive than others. Mostly limestone rock bottom where I fish so i can't tell. i know they are there because i sometimes see huge shells washed up on the shore.

If using a crankbait and you have a good feel for what the bait is doing, you should be able to feel just a slight difference between rocky bottom and shells. Also, you'll pick up small shells on your hooks. If using a jig or c-rig, again you should be able to feel a difference, plus you'll often get shells on your line just ahead of the jig or weight.

Are certain areas more productive than others - you bet. How you determine them beyond catching or not catching fish is beyond me.

i would think current would be a major factor in their location as they are filter feeders.

they show real good on a HB SI unit....rick