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Fishing one Whales takes 4.5-11.25s (which Dragon Fishing Rod and Fishing Amulet), so 7.875s on average.
That's 7.62 fishing actions per minute or 457 per hour.
Each actions grants at least four whales, so 1828 whales per hour.
+5% to receive 8 whales from Pudding Duckie, +10% from Aorpheat's Signet Ring, +12% from Fishermans Potion IV, +5% 50% Mastery Pool Checkpoint, -3% to receive special items instead of whales = +29% = 2359 whales per hour.
Each sold at 750g = ~1.77M per hour.