When I was a kid, you could always find fresh mullet for 9 cents a pound in the local supermarket.
I recall Mother showing me how you could tell if they were really fresh by looking at their eyes. If I remember right, they would show just a hint of red if they were over a day old.
When buying “fresh” fish, trust your eyes and nose.
Eyes should be bright and clear.
Lift up gill plate. Inside should be bright red. Then stick your nose in. If it smells “fishy”, don’t buy it.