Just go to eldrich zone on crystal isles and look for big bubbles that have some black clams/oysters inside of them, put your angler fish inside the bubble, harvest, and enjoy the best black pearls harvester in the entire game, super easy, rank up for people to see this.

first tame an ichthy then go to rag about 75,23 more black pearls then you can carry on the sea floor and not to dangerous just keep an eye out for megs

When you want black pearls in great quantity, here are some things I suggest.
1: Ragnarok: Vikings bay. Bring a good crossbow to one shot any water scorpions, they drop TONS of black pearls.
2:Extiction: Gachas. Sometimes when taming gachas, you can get one that produces black pearls. They produce in big quantities, and for me is by far the safest and easiest way to get the black pearls. Like if this helps!😄

I'm on mobile and usually play on unofficial but the way I get tons of black pearls and bio tox is just get a high lvl basilos then go around the sea floor and just kill everything

On mobile what i do is just tame a basilo and bring 3 pairs of scuba tanks and some flippers. Then go to the bottom and watch the basilo’s health then kill euryptarids and ammonites.

Tame a crystal wyver then go to crystal isles where all the squids spawn and start killing the "beached" ones. Ez black pearls

Ragnarok in Viking Bay around the sunken ship in the middle of the bay and also at 10 90. There’s a tiny tip of a Boulder to land a flyer out there. The water is shallower in that area. Another sunken ship there with lots of lobsters to kill.
Aberration down in the red hazard zone. They can be picked up off the ground down there.
Genesis in the volcano biome. Down in the Magmasaur pit they can be picked up off the ground there too.

I still have not found a way to gather pearls with a tuso but the GACHA is through its production lines

Gachas get about 60 per good crystal if you’re lucky or they get 25-30

When low level tame otter and make it kill fish there is a chance it will get a black pearl