Nicky’s Plaice

Cathal’s review pretty much sums it up.
All I can add is that, when in doubt, follow the local knowledge. For many years Nicky’s Plaice is where most indigenous Howth people have bought thier fresh fish.
As an added bonus you can usually spot a few seals from the adjacent waterside.

You may talk of your Beschoff’s and all other sorts of codology (there’s a pun), but to get the finest, freshest fish, it has to be Nicky’s Plaice (there’s another).
Now, if you ever happen to visit the fine village of Howth (and sure why wouldn’t you, it’s a lovely spot), you might take the notion to buy some fish. Howth is Dublin’s main fishing port, so that’s where you get fish at it’s freshest. The fishmongers in Howth are all located along the West Pier, as this is where the fishing boats dock, so it’s handiest for processing and selling the fish.
The first fishmonger along the pier is Beschoff’s, next to the restaurant also owned by Aidan Beschoff. For heavan’s sake, don’t be seduced by the familiarity of the name, their fish just isn’t up to scratch. And there’s a number of other fishmongers along the pier on the way to Nicky’s. Now, these fishmongers are very good, and are an ample substitute when Nicky’s isn’t open. But for the best fish in Dublin, you have to go almost the whole way along til you get to Nicky’s.
Oh the fish, the fish! Smoked salmon, sole, scallops, whiting, cod, sea-​bass, it’s all fantastic. They sell according to what’s been landed, so if there’s been a catch of squid landed, calamari is what you’ll be having for dinner. Unsure of what to get? The lads behind the counter will be happy to help.
You won’t get better fish in Dublin. Fact.