I don’t know exactly how those particular people did it but they may have used something similar to a fridge which I actually bought some forty years ago and which was based on an ancient Egyptian device.
Basically it was a box made of clay and on the top was a depression which you filled with water. The water soaked into the box and due to evaporation of the water content in the clay kept the contents cool.
If they sold the fish near the seafront they could have kept the fish cool in smaller nets in the water too I expect.
Only coastal residents would enjoy eating fresh fish. In the Mediterranean area, fish was smoked and then dried and salted. Roe was pickled ready for transport inland. Dry Cod was a common trade commodity, started with the Vikings.
I was going to say, I was under the impression that any fish not eaten right away for that night’s dinner would have been smoked and dried before sending it on to market.
Somewhere on the shore of the Sea of Galilee, though nobody seems to know exactly where, there was in antiquity a place called Tarichaea, named several times in Josephus’ books. This Greek word has to do with the preservation of freshly caught fish for the market, either by salting or by pickling.
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