I visited this site in 1984. The ‘fish preserves’ was a sauce made from tuna. The little town had its own pottery which made ceramic jars to hold the sauce, which was shipped all over the ancient Mediterranean. When the tuna fish vanished, either over fished or migrated elsewhere, the fish sauce industry died.
This city is interesting in that the entire geologic strata on which it it located has buckled from tectonic pressure between the interaction of African and European plates at that location. When one walks down the main road toward the sea it looks as though the swells of the sea moved inland and froze. Not surprisingly, all that's left of the original buildings is their foundations.
The town must have been abandoned in the late Roman Empire period, as it wasn't built over.
This was not a major city, like Cadiz, originally founded by the Phoenicians. It was a small, provincial town, and as such is quite interesting and worth the visit if you are ever in the area traveling between Cadiz and Tarifa.
Thanks! Glad there are some first-hand observation here.