Back in the days when no to very few households have refrigerators, salt is widely used as preservation technique. It works by binding free water in food rendering it unavailable for microbial use. Dried fish is okay but dried salted fish is much better. Over salted and kidney damaging variants are made to lasts, not to fill gastronomical desires.
So rubbing salt to freshly bought market fishes has a bit similar effect. From fishing boats, loaded in large bins and filled with ice. Immediately after someone bought, the ice will thaw providing endless room for spoilage bacteria to attack. Salt attracts water from inside out. This practice makes the commodity lasts for a bit, just enough to last before frying, which is the usual end, purpose. Parts for sinaing must go to clay pot right away. Vinegar is the main keeping ingredient of this one.
Household refrigerators are pretty common now. Whichever not set for immediate menu are thrown inside freezer. No salt, no poor salt! Those calling for special flavours are soaked in liquid of desired mix. But, still, stored inside chiller.
Salt scrubbed to fish not only served as shelf life extender, great flavoring too, imo. There were times that I preferred the toasted salts and its dark colored cooking oil. Giving away the fish and contented with it as rice topping. Full stomach after two to three unhealthy servings.
I missed it. So, I rubbed some rock salt to last piece of tulingan right before frying. I got an old school fried fish but failed to recreate the toasted salt. I am blaming the cooking style for this. I used the combination of induction stove and low temp. It is way too far against strong wood fire and wok.
Note: fish taste best if cooked and eaten promptly after catch.