Merfolk Control

What's the reason you put Master of the Pearl Trdent, an aggro card, into a control deck?
There are so many Merfolk cards you could use, that have a control aspect, that I don't see why you should play Augur of Bolas or the Master. Talrand may be good as a 1 drop but there are also even sronger cards in the game.

There are a lot of cards that benefit from interaction with an opponent, for example Brineborn Cutthroat benefits from spells you play during an opponents turn to get stronger permanently or Cosi's Trickster (shuffling an opponents library) or even Wake Thrasher (the more lands you tap for mana, the stronger it gets).

Other cards can control opponents like Dakra Mystic, which can cause every player to either draw or waste the top card of their decks. Grimoire Thief lets you exile the top cards every time it gets tapped and you can also sacrifice it to counter spells exiled if needed. Merfolk Windrobber also shrinks the library and you can sacrifice it to draw a card, for example before it gets bolted. Riptide Pilferer targets cards in your opponents hand instead.

Cards that benefit from massive counter spam are first and foremost Lullmage Mentor, which generates tokens and also free counters while playing, while Sigil Tracer lets ya copy your and/or opponent's spells easily. Tazeem Roilmage is not that big of an impact but I added it because you can get your spells back if you want (it's not as strong as Snapcaster Mage but ok, depending on your desired power level). Umara Wizard dosen't interact with your spells on the same level as Lullmage Mentor but it could be a free drop for your deck as it is a dual sided card which can also be playeds as mana source.

Some cards that have control aspect in case of keeping the board clean are for example Harbinger of the Tides, Razorfin Abolisher and Surgespanner, which all have the ability to return permanents to their owner's hand. Merfolk Trickster is a different kind of usecase as it doesn't return cards but removes creature's abilities for a turn.

What's a good control deck without any stealing, fortunately, there are at least 3 cards I can suggest to steal opponent's stuff. Rootwater Matriarch permanently get's control of creatures that are enchanted, regardless of if they remain enchanted. Thada Adel, Aquisitor and Thieving Skydiver both can grab opponent's artifacts and Skydiver also has the ability to equip them, so it plays really well with Colossus Hammer to get a 12/11 creature for {1}{U} + {1} for it's Kicker cost.

Last but not least Kopala, Warden of Waves as your counter-buddy to protect the one or other Merfolk or even a Mutavault from being targeted.

You see there is so much more potential in Merfolk than Talrand, you just have to utilize them