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Technique and maintenance in the ancient fishponds

by Eugenia Salza Prina Ricotti

Technique and maintenance in the ancient fishponds

Though now let have a look to the technical part of the Roman fishponds. We know them and we know how they were made. We find all those data in Columella one of the writer on agricultural history who, more than any other studied them. Columella begin by censuring the frenzy to have one, admitting that it could be done only if the seaside estate on which it had been made was barren and sterile. Then he went on describing what kind of fishpond was adapted to a certain kind of coast. The ones made on muddy bottoms, the ones on sandy ones and the rocky ones. In the first one flat fishes as soles, brillsm and many kind of bivalves as oysters, clams and cockles. In the others which stood on sandy bottoms you could also breed soles and brills, but they were the best for fishes from the depth like gilt-heads, and sea breams. Then in the rocky ones which were the best of alls and there one could have fishes that live in holes of the rocks like morays.
Then Columella goes on listing the rules necessary to maintain in good order the fish ponds. Wherever they had been built what was absolutely necessary to them was the change of its water which staying there had lost oxygen. After it, it was wise to create places where in the hot hour of the day the fishes could find a shelter from the sun (Aestivatio); then it was a good practice to infuse in the basins fresh water (Aquatio) as the mixing of the two kind of water improved the quality of the fishes.
Now let us have a look to the fish ponds with a muddy bottom. These basins usually had a depth of 60 cm at they were built on the coast but pushed inward the sea. In them water was changed when the tide covered them, but it was necessary that in this moment the fishes didn’t get out, thus all around them nets were set tied to a sequel of poles infixed on the basin’s edge. Besides to avoid that the gales could destroy them or fill them with seaweed piers were built with opening formed as meatus, in such a way that they could let water filter but block the waves.
For the other fishponds which for the kind of fishes kept in them needed more depth and which as they didn’t go in the sea couldn’t be submerged by the tides, the change of water was made through canals who put in them new water from the sea and chased the old one. Columella advised to have two canals, one the entering on one side, brought the new water, through the other the old and spent one got out. Really to have one or two canals must not have been very important as in the splendid Sperlonga’s canal there was only one.
Of course the canals for changing the fishponds water were set according to the positions of the basin with regard to the coast. When the level of the coast on which the fish pond had been built was higher than the sea (see the Sabaudia’s case) the canals arrived. directly on the bottom and this was also the best for the fishpond. Instead when the basin had been dug in the ground the canals arrived at its top.
In both the cases the mouths of the canals were protected by diaphragms made by flat bronze pieces filled with holes which let water go in but didn’t let the fishes go out. The same kind of diaphragm were set to the different basins of the fish ponds to keep the different kinds of fishes divided.
After this Columella goes on explaining how to feed the fishes because now they couldn’t go to find their own food in the sea. For the flat fishes in they low basins there was no need of large expenses, but feeding the fishes kept in the rocky ones was very expensive. Their owner must maintain a real fleet of fishing boat because the fishes they bred in them didn’t accept anything else than shrimps and small fishes, but thy had to have been just caught. Only in case of bad weather they could offer them bread, season fruits cut in little bits and a dessert of dried figs and it was highly recommended never to forget them.


Bibliography
- E. SALZA PRINA RICOTTI – L'importanza del pesce nella vita, nel costume e nell'industria del mondo antico in Rendiconti Pontificia Accademia di Archeologia Vol. LXXI, 1998-1999 pp.111-165