In order to keep their catch alive (and fresh) until they return to shore, fishermen have traditionally used "stringers" to suspend the catch over the side of the boat. What was thought to be a more modern invention was the "livewell," a container on board supplied with circulating water. Now archaeologists have discovered evidence that livewell technology was used by the Romans in the second century.
Consisting of a pumping system designed to suck the sea water into a fish tank, the apparatus has been reconstructed by a team of Italian researchers who analyzed a unique feature of the wreck: a lead pipe inserted in the hull near the keel... Indeed, a number of historical accounts have suggested that the Romans might have transported live fish by sea. For example, the scientist and historian Pliny the Elder (23 – 79 A.D.), wrote that live parrotfish were shipped from the Black Sea to the Neapolitan coast in order to introduce the species into the Tyrrhenian Sea.
Measuring 51 inches in length and featuring a diameter of at least 2.7 inches, the unique lead pipe was located in a sort of "small bilge-well" and would have been connected to a hand operated piston pump (which had not been found within the wreck).
Additional details are at Discovery News. Schematic diagram by Simone Parizzi.