Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
"Formerly," says Varro, "the barn on the estate was larger than the manor-house; now it is wont to be the reverse." In the domains of Tusculum and Tibur, on the shores of Tarracina and Baiae-- where the old Latin and Italian farmers had sown and reaped-- there now rose in barren splendour the villas of the Roman nobles, some of which covered the space of a moderate-sized town with their appurtenances of garden-grounds and aqueducts, fresh and salt water ponds for the preservation and breeding of river and marine fishes, nurseries of snails and slugs, game-preserves for keeping hares, rabbits, stags, roes, and wild boars, and aviaries in which even cranes and peacocks were kept. But the luxury of a great city enriches also many an industrious hand, and supports more poor than philanthropy with its expenditure of alms.
Those aviaries and fish-ponds of the grandees were of course, as a rule, a very costly indulgence. But this system was carried to such an extent and prosecuted with so much keenness, that e. g. the stock of a pigeon-house was valued at 100,000 sesterces (1000 pounds); a methodical system of fattening had sprung up, and the manure got from the aviaries became of importance in agriculture; a single bird-dealer was able to furnish at once 5000 fieldfares--for they knew how to rear these also--at three denarii (2 shillings) each, and a single possessor of a fish-pond 2000 -muraenae-; and the fishes left behind by Lucius Lucullus brought 40,000 sesterces (400 pounds). As may readily be conceived, under such circumstances any one who followed this occupation industriously and intelligently might obtain very large profits with a comparatively small outlay of capital.
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Reference address : https://www.ellopos.net/elpenor/rome/5-11-old-republic-new-monarchy.asp?pg=98