Old pic of the Depot Ship in the Holy Loch in Scotland in the days when the US Navy was resident there.
If I remember correctly, CANOPUS was one of the US Navy ships to come over to Hartlepool for demolition.
Sorry, no details of the YFN I'm afraid but I'm sure someone will be able to fill you in! The puffers were regular attenders as they took away all the rubbish, quite a job for them in their declining years.
Chadburn, the USN built hundreds of these 'covered lighters' .
They were simply freight barges, some powered and some not.
The YFNB type were designated as large freight barges, the one shown originally carried ammo I believe.
The cargo ship alongside USS Canopus is probably USNS Marshfield (T-AK-282), a Victory Ship built during WW-II that had been specially-modified to transport ballistic missiles. Holy Loch was one of her regular stops for many years. See below: