Merfolk: Guide To The Most Magical Creatures of the Sea

SeaPro-The Plant-Based Protein Merfolk Eat

Author's Note-I haven't updated this in years, so this may not flow well as part of the "guide", but this is a new worldbuilding idea I have for merfolk food that is "open source" in the sense anyone can feel free to incorporate it into their mer-fiction.

Merfolk diets are traditionally ostrovegan, which means vegan except for bivalves(oysters, mussels, clams, and scallops). Bivalves are likely not fully sentient, despite being technically animals. Like some human indigenous tribes, they use every part of bivalves, harvesting their shells and pearls for clothing and accessories. 

In addition to bivalves, the main source of protein and other nutrients in their diets is what they call "SeaPro"(short for "seaweed protein"), a tofu-like substance made from red seaweed. Red seaweed is surprisingly high in protein, and in the form of SeaPro, it can be prepared many different ways. Just about every merfolk kingdom has their own traditional SeaPro recipes, with some, for example, preferring to eat it heavily seasoned or cooked over thermal vents giving it a texture similar to deep-fried tofu. 

Merfolk can communicate as equals with most sea creatures, and some fish, crustaceans, and occasionally marine mammals live alongside them in their communities, with some even evolving to be, for a lack of a better word, "civilized" enough to eat what merfolk eat instead of their natural predatory eating habits. While merfolk respect all sentient sea creatures, large predators such as most sharks and killer whales are more difficult to befriend. They tend to get along best with small fish and crustaceans.