Forty ships have been called up for Middle East service from the Ready Reserve Force, the fleet of old civilian cargo ships maintained for quick deployment in national emergencies, the Transportation Department said yesterday. It is the first time the ready reserve has been called up since it was formed in 1976.

Transportation Secretary Samuel K. Skinner said additional ships are expected to be activated by Friday. The fleet will ferry weapons, supplies and aircraft spare parts to the Middle East, supplementing military and civilian craft already pressed into service.

Many of the reserve ships have become a familiar sight for boaters and motorists in various locations around the Pacific, Gulf and Atlantic coasts where they sit moored side by side, year after year. About half the 96 ships in the fleet are moored in the James River in Virginia; at Beaumont, Tex., or at Suisun Bay, Calif., near San Francisco.

Thirteen of the ships are at sea under Navy orders announced yesterday. Another 12 are being readied and 15 additional ships were ordered readied during the weekend.

Walter Oates, a spokesman for the Maritime Administration, which maintains the ships, said the activated fleet includes 17 roll-on, roll-off vessels for heavy weapons, 13 ships for general cargo, five barge-carrying ships, two aviation logistics supply ships to haul sensitive aviation spare parts and two auxiliary crane ships capable of loading and unloading container freight. Another ship will be designated later.

The ships are crewed by civilians supplied by maritime unions, under the Navy's Military Sealift Command.

The reserve fleet was formed in 1976 as the U.S. maritime industry fell on hard times and the merchant fleet began shrinking. The Maritime Administration buys at scrap cost ships that have become surplus or are outmoded.

In the past decade, ocean shipping switched largely to bulk ships or ships that carry containers suitable for loading onto rail flat cars or truck chassis for ground movement. That left many classic "break-bulk" ships -- easily identified by a deck full of hoisting cranes -- on the market.

The Maritime Administration occasionally buys new ships and retires others from the fleet. The fleet includes some World War II Liberty ships, but none of those were called up among the initial 40 ships.

The ships are maintained in three categories according to the amount of time needed to place them in operation -- five days, 10 days or 20 days.

The top-priority ships are maintained to the point that they can be readied in place and move under their power, with dehumidifiers protecting the interior and steps taken to protect the hull from corrosion.