Gathering Breeding Materials
Most dolphin and porpoise species in Wonderoussea require raw cod or raw salmon to breed. Collect these from fishing or by hunting natural fish. Some species, like Spinner and Dusky dolphins, prefer a bucket of tropical fish instead—craft this by placing tropical fish in a bucket at a crafting table.
Finding the Right Species
Different dolphin varieties spawn in specific ocean temperatures. Warm oceans host Bottlenose and Common dolphins, while cold oceans contain White Sided dolphins and Right Whale dolphins. Mangrove swamps are home to Tucuxi river dolphins. Travel to the appropriate biome and locate a pair of the species you want to breed.
Breeding and Rewards
Approach two dolphins or porpoises of the same species and right-click each with your chosen food item. After breeding, Common dolphins may drop a 
Harmony Stone as a gift. Porpoises drop Porpoise Flukes when they hunt, which you can use to brew Porpoise's Grace potions. Keep pairs together near your base to establish a breeding population for steady resource generation.