Joseph - most everyone has packed their gear away and are refilling the family cookie jar right about now. Maybe 10% of the people still have a line in the water on occasion... Some others may be saving a fishing secret or two
As for castle Island and shore cod, they do occasionally get them there but it's not an enourmous fishery. I would recommend the sweetest clams you can get, and either fish the edge of the outflow of the Sugar Bowl o r stick at the pier. Keep in mind that if you get a legal fish, have a plan for getting it up the pier.
Personally, I have only fished there a handfull of times in the past 6-7 years and before that nearly 20 years ago, so I don't have too much to add.
I don't know the smelt fishing there but it tends to be decent in the Quincy area.