IN some places a young man's fancy is expected to turn to love. But from Virginia to New York shad roe is a powerful diversion.

Herring, mullet and rock fish roe are also fancied, and at the moment some markets stock flounder, perch and carp roe. But, "in the spring, you primarily see shad roe in this area," according to Clare Vanderbeek, seafood consumer specialist in the Office of Seafood Marketing of the Maryland State Department of Economic and Community Development.

Shad and shad roe are usually sold separately in Washington markets--the roe can be worth more than the shad itself. The butterfly-shaped pairs of roe range from light gray to light brown; Vanderbeek emphasized that the eggs should be attached and close together in the roe when it is purchased. If the eggs are pulled apart or separating, that's a good indication they may be getting old. The roe should have a fresh, ocean-air smell, but not a "heavy, fishy smell," cautioned Vanderbeek, and should not feel slimy or slippery.

With regard to size, Vanderbeek said, a small roe ranges from 3 to 4 ounces, medium roe from 4 to 6 ounces and the larger roe from 8 to 10 ounces. She added that the larger or jumbo shad roe may be purchased closer to the New York market because as the shad migrate farther north, they and their eggs grow larger.

Once the roe is home, Vanderbeek suggested that it be stored in the refrigerator in a well-wrapped airtight plastic no longer than 3 days, as it tends to dry out with longer storage. She discouraged freezing the roe, but added that, if frozen fresh, the eggs should not be kept longer than 3 months.

Shad roe is widely available from March through May in Washington supermarkets and seafood markets; a survey of seafood markets also found the following stocked with other fish roe:

Daniel's Cellar & Sea (102 S. Alfred St., Alexandria)--Perch with roe (roe free), 1.49/lb., Feb. through April; flounder with roe (roe free), 2.29/lb., May through mid-July and Dec. through Feb.

Old New Orleans Seafood Market (6232 Old Dominion Dr., McLean)--Flounder roe, .50/lb., May through mid-July and Dec. through Feb.

U.S. Fish (10576 Metropolitan Ave., Kensington)--Carp with roe, 1.09/lb., March through April; perch with roe, 2.19/lb. (Feb. through April).