Winter flounder can be found at the mouth of the Merrimack and along the shore of the refuge. Much better fishing in Beverly, Salem and of course Boston Harbor but those could be an all for you. Very occasionally you will hook a summer flounder but it's not very often.
Almost every pond in eastern mass has crappies in it. Most are pretty small but you can get a slab every now and then. They hit small spoons and/or twirly tailed grub lures
Try near the jetty on the northern side in the river. Or Sand Point at the southern tip both have good fishing. Parking will be an issue along the main beach unless you live in Newburyport
Those were hornpout/bullhead which is a small species of catfish. Pretty much every pond will have some of those guys in it, don't get very big or much fishing attention