Then why not playing Grim Long again?
I tested both Long versions, and I like the 4 Duress + 1 Swarm a lot. Pitching blue cards can be very hard.
So I switched back to Grim Long.
IMHO the versions are not 100% different: sometimes a game is the same with Grim Long as it would go with Pitch Long.

Only because of your primer and your SCG report I decided to get the cards and play Fish. It's a very good deck. Ok, you don't get to make broken moves - but winning with white 2/2 creatures in Vintage is fun!

I don't like Misdirection, too. Supporting 4 FoW is hard enough sometimes. 1 or 2 more pitch spells is overkill. I switched Misdirection for Daze two weeks ago and it worked very well. Daze is a good addition to the mana denial strategy of Fish. I also think you want three of them, so I cut the 2 MisD and 1 Sword. I like True Believer a lot.

Is the Ichorid matchup so bad? Last month, my friend and I were both playing Ichorid and we feared fish. Jötun Grunt, Swords, Wastelands and Jitte can ruin the day.

I don't understand the Polluted Delta. Sometimes the deck plays like White Weenie with a blue splash, so I play 2 Windswept Heath. I often keep a fetchland for Brainstorm, and after a Brainstorm I want to fetch a white mana. But I don't think it makes a big difference.

Thank you for the primer and the report.

To Dave Feinstein!

Is it instant or sorcery speed?

I couldn't find the meaning of "Éphémère", but in the flavor text the word "instant" shows up, so this word exists in french.

So it must be a sorcery?

The Grunts are evil.

A blue instant would be the best choice for removal in this amazing deck.
You have a full set of Merchants Scrolls to look for it.

Maybe silly ideas – but i thought about Psionic Blast?

Stealing the Grunt and not paying the upkeep could also work.
Dominate is a blue instant (would cost 3UU) or Seasinger could do the job.

It's off-topic, but does anyone play seasinger in the gifts sideboard?

Seasinger
1UU
Creature - Merfolk
0/1
When you control no Islands, sacrifice Seasinger.
You may choose not to untap Seasinger during your untap step.
: Gain control of target creature whose controller controls an Island as long as you control Seasinger and as long as Seasinger remains tapped.

The island on both sides of the table shouldn't be a problem. It can steal DSC and Oath's creatures. But Seasinger is easy killed by the typical */1 removal in today's metagames. Is it worth a look, for the players with 1-2 Old Man of the Sea in their sideboard?