Mer-foods

In my studies of the merfolk I have amazed them with my foods and been horrified and disgusted by theirs.  It can not be called a cuisine. Raw, mostly unpleasant consistency and unbearable flavors. Much of this must be attributed to their primitive and difficult living situation in the sea.  Fire is rare and mystical, and can only be made ashore with difficulty. Fire makes air in underwater caves or buildings deadly for air breathers. They have no simple seasoning - the water washes it away unless it is a thick and oily paste. Raw fish. Raw mollusks. Raw sea weed.  Other strange creatures and plants, always raw. Frequently best if just swallowed whole, if possible and unchewed.

Imperial Scholar Maruno Ito. "Studies of the Merfolk"  (Imperial year 1377).

 Imperial Library. LanHou, Holy Isle of Kuan.

Merfolk species may be found in the oceans of the world.  They are seminomadic with few consistently settled "Homes" or communities. Some will return to caves or other settlements seasonally or for significant rituals or cultural events.  A few have learned stonework construction, shaping stone with recovered tools and metal from shipwrecks, pirating or raids.  The universals of their life are water, , dark cold and limited tools.  
Merfolk engage in limited farming of seaweeds and other plants, or even tending kelp groves.  They primarily are hunters with some foraging. Life underwater precludes building or using fires.  A few have found hotwater springs and volcanic vents where "cooking" may be performed. This is net or spear held out over the hot water flow. Most do not have this luxury. Merfolk have very limited spectrum of taste flavor - umami, salty and bitter.  Water is as air to them and gets into every attempt at a sealed container.  They have no soups. No sauces.
Typically food is presented "as caught" and the individual simply takes bites, or ingests the whole of a food item- fish, shellfish, crabs, squids or what have you.  Frequently not fully dead- as live food is deemed fresher and better.  Large prey may be cut up into smaller portions and may include seals, narwhal, whales and great sea monsters.  These "smaller" portions are strips or chunks that are chewed upon. Sailors taken in pirate attacks of ships may also grace the merfolk diet.  They do not typically have utensils, plates or even specific dining places - eating with hands where they are.
A source of great interest are ales, wines and brandy.  The merfolk are unable to create fermented foods or brew. Thus alcohols are very powerful to them since it is alien to their life. Many an attack on shipping has been bought off by surrendering ale, rum or other alcohols to the merfolk.