June 3, 2011 -- Found in 1986 six miles off the coast of Grado in northeastern Italy, this Roman shipwreck was recovered in pieces in 1999. Dating from the second century, the 55-foot-long, 19-foot-wide trade vessel was packed with some 600 vases called amphoras.They were filled with sardines, salted mackerel and garum, a fish sauce much loved by the Romans.
Recently, archaeologists found signs that the Roman sailors maintained an oxygenated water fish tank on board the ship.
This 51-inch-long lead pipe was located in the stern area and fed into a hole bored in the ship's hull.
The unique lead pipe was located in a sort of small bilge well (visible around the tube) and would have been connected to a hand operated piston pump (which was not found within the wreck). Sucking the sea water in a fish tank on the deck, the apparatus could have turned a simple small cargo vessel into a ship able to carry live fish.
The researchers were particularly intrigued by this hole in the keel, made to host the lead tube, which was 2.7 inches in diameter.
"No seaman would have drilled a hole in the keel, creating a potential way for water to enter the hull, unless there was a very powerful reason to do so," researchers noted in the International Journal of Nautical Archaeology.
This diagram shows how the hydraulic system might have worked. The researchers calculated that the small trade vessel could have carried a tank containing around 4 cubic meters (141 cubic feet) of water, which could have housed 440 pounds of live fish.
Connected to the lead pipe, the hand-operated piston pump would have easily allowed the necessary exchange of the water mass. According to the researchers, the water would have needed to be replaced once every half an hour in order to provide a constant oxygen supply. With a flow of 66 gallons per minute, the piston pump would have filled the tank in 16 minutes.
A 3D model of the ship with the fish tank is shown. The fish tank was likely placed on the deck in the aft area, behind the mast.
The water mass of the large tank would not have posed any stability problems and could have housed live fish, such as sea bass or sea bream.