Cecil, it was a navigation channel as I recall...
I am not sure I can find a source for the native fingernail clam. I am definitely going to give it a hard look this year... If anyone has fingernail clams in there pond, let me know and send them my way! I have seen them before in the area, just a matter of finding them again and collecting them. The Asian clam is all over the place, no problem finding it...
