I've been reading this question about agriculture for merfolk and more specifically the accepted answer. They mention the problem of food preservation only minutely. Now I'd like to pour that thought into a question proper: How would an aquatic species store and preserve food? Let's assume that the main food sources are fish, followed by kelp/seaweeds and shellfish.

Some ideas I had myself, but they don't touch on storage or may have flaws I'm missing:

  • As the comments on the linked question discuss: somehow cure the meats using heat vents. Perhaps use air bubbles to keep dry?
  • Do as some prehistoric gatherers did: simply store meats in a location with a very cool flow of water which supposedly slows down decay.

Storing and preserving food should be one of the easier tasks for merfolk.

There are some places undersea that are excellent environments for preserving organic matter. For example, cold, low oxygen parts of the bottom of the Black Sea, Per National Geographic:

In most seawater, wood and rope are among the first things to decay. But the unusual water chemistry of the Black Sea dramatically slows rates of disintegration. Many of the shipwrecks that Adams and his team found were in depths below 150 meters, and some lay as deep as 2,200 meters below the surface.

The wood of some ships was so well-preserved that chisel and tool marks were still visible on individual planks. Rigging materials, coils of rope, tills, rudders, and even carved wooden decorative elements have survived the centuries largely intact.

“Nobody has seen anything quite like this before,” Adams says. While historical texts and illustrations give some information about the appearance and construction methods of merchant ships in different periods, Adams hopes the extraordinary preservation of these wrecks will allow archaeologists to independently verify those historical records.

British and Irish bogs and similar, muddy, shallow water, low oxygen environments are also good place for preservation of food. Researches have recently recovered 3000 year old butter stashes in these bogs. At that point it isn't yummy, but it is still edible. There is a picture of it below:

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Honey can also make an excellent long term preservative (also thousands of years) and being underwater where it is cool, protected from light and is protected from bears and insects and people who like to raid and eat it (sea animals don't seem to have as much of a sweet tooth as land animals do), are all a good fit. Obviously, the merfolk couldn't make honey themselves underwater, but this could be something that the desire as a trade good in exchange for something else.

And, of course, don't forget one of the most common premodern preservatives, which is salt: salt meat including beef and fish are some of the oldest foods with long shelf lives and the oceans have an abundance of salt.

Salting, either with dry salt or brine, was a common method of preserving meat until the 19th century. It was frequently called "junk" or "salt horse".

Salt inhibits the growth of microorganisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to kill most species of unwanted bacteria. Smoking, often used in the process of curing meat, adds chemicals to the surface of meat that reduce the concentration of salt required.

Salted meat and fish are a staple of the diet in North Africa, Southern China, Scandinavia, coastal Russia, and in the Arctic. Salted meat was a staple of the mariner's diet in the Age of Sail. It was stored in barrels, and often had to last for months spent out of sight of land. The basic Royal Navy diet consisted of salted beef, salted pork, ship's biscuit, and oatmeal, supplemented with smaller quantities of peas, cheese and butter. Even in 1938, Eric Newby found the diet on the tall ship Moshulu to consist almost entirely of salted meat. Moshulu's lack of refrigeration left little choice as the ship made voyages which could exceed 100 days passage between ports.

enter image description here

Salt Fish hanging in a Hong Kong market in 2011 via Wikipedia

@John also has a good point about live storage. Most Asian grocery stores in the U.S. sell very fresh fish and seafood by having at least some varieties live in tanks in their stores until it is purchased, and this would be a natural approach for merfolk.

enter image description here

Live lobster storage as a grocery store via Wikipedia

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    $\begingroup$ I agree with much of this, and the trading for preservatives (honey) part is clever; however, environments such as that within the Black Sea, or low oxygen bogs, may be just as hostile to merfolk as they are to bacteria - they may just not be reachable. $\endgroup$ – Zxyrra Nov 17 '16 at 3:41
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    $\begingroup$ The merfolk could make seaweed rope and lower the food to be stored in buckets or casks down to the cold, low oxygen areas and pull the food back up when needed, a bit like storing food at the bottom of a well (another historic food preservation trick). $\endgroup$ – ohwilleke Nov 17 '16 at 4:02
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    $\begingroup$ I actually disagree with the use of salt in this context - its preservation qualities come when it is concentrated, which would be genuinely hard in the sea. On land, we can dry salt and use in concentration at a low tech level, while under the sea - even if they could concentrate it into a brine, it would be hard to keep it from re-diluting, and anything munching on it can deal with the baseline salt level anyway. It could be done, but it would be tricky and take roughly the same tech level as we needed for making containers airtight or separating or transferring gasses. $\endgroup$ – Megha Nov 18 '16 at 0:27
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    $\begingroup$ Another option would be pasteurizing basically. Put your container full of food in an underwater hot spring or geothermal vent sterilizing it, and seal it (perhaps with something waxy). $\endgroup$ – ohwilleke Nov 18 '16 at 0:33
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    $\begingroup$ @ohwilleke This sounds like something extra to add to your answer $\endgroup$ – D-zap Nov 18 '16 at 8:06


From wikipedia:

Pickling is the process of preserving or expanding the lifespan of food by either anaerobic fermentation in brine...

The rest is just academic. You can pickle things by soaking them in brine. So pretty much everything that merfolk are going to eat is going to be at least a little bit pickled. Any developing merfolk society is going to probably start from pickling and develop other food preservation methods from there.

Vinegar is an obvious next step, since that is the other main component of pickling. Vinegar is produced by bacteria fermenting foods, so there is no reason it would not work underwater. The challenge would be to make a watertight container that you could put your fermentation materials, along with seawater, to let the bacteria do its work.

Once you have a container full of vinegar, you could use a hand pump to move it to another container with things that you want to pickle. Conceptually, it seems hard to think of a good way to transfer liquids between containers while immersed in another liquid, but I have confidence that merfolk growing up in such conditions will have more imagination.

The list of things you can pickle is long, but importantly, contains both fish (delicious pickled herring) and seaweed (like Japanese su kombu).

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    $\begingroup$ "Conceptually, it seems hard to think of a good way to transfer liquids between containers while immersed in another liquid": Treat transferring liquids while immersed in a liquid, as we humans treat transferring gasses while immersed in a gas: 'Liquid cylinders' to our gas cylinders $\endgroup$ – D-zap Nov 17 '16 at 10:55

live storage is always an option, cages would let shellfish feed until you are ready to eat them, they work fairly well for fish too.

canning/jarring would still work but they would need to get those things and would need to use deep sea vents to cook them.


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