No-one was awake on the bridge when the German-owned MV Danio ran aground on the Farne Islands, off the Northumberland coast, despite the Longstone Lighthouse's warning beams flashing across the sea, Newcastle Crown Court heard.
Judge Brian Forster said: "There could have been a major maritime incident."
The Danio set out from Perth, Scotland, on the evening of March 15 last year, carrying logs destined for the Belgian port of Ghent.
At around 3am the following day, the Chief Officer, who was in charge, fell asleep on a settee on the bridge after putting in eye-drops he needed for an infection. There was no look-out among the six crew.
An alarm which sounded a warning if the bridge was not manned had been switched off because the crew found it irritating, the court heard.
They woke up 90 minutes later with the noise of the vessel running aground on rocks.
It hit a reef head-on, then pivoted 180 degrees, getting stuck fast on the outcrop.
The court heard that the Farne Islands are an internationally-renowned wildlife haven, famed for their sea birds and grey seals.
No-one on board was injured and there was no leakage from the vessel, despite it being badly damaged. The Danio was only removed 12 days later following a tricky salvage operation.
Judge Forster said: "The potential for disaster is obvious. In my judgment there was a lack of effective management, which allowed the situation to come about.
"Clearly, any vessel operating silently at night without a look-out is a moving danger and a threat to any other vessel which may be on the seas.
"Fishing boats set out from the ports along our coast and ferries come from the Tyne."
He fined the defendant, Cuxship Management, £60,000 after the firm admitted two breaches of maritime regulations. He also ordered it to pay £12,796 prosecution costs.
Christopher Knox, defending, said the operator has instructed that the bridge alarm must not be turned off in future, and that measures are now in place to make sure all crews employed are correctly qualified.
Outside court, Alan Thompson, of the Maritime and Coastguard Agency's Tyne Marine Office, said: "It is very fortunate that the damage to the MV Danio was relatively small and that there were no injuries or deaths.
"It is also fortunate that the effects on such an environmentally sensitive area as the Farne Islands were minimal."