Grey pearl caviar by John Spottiswood.

Paddlefish swim in Southern rivers and they're relatives of sturgeons--the fish that produce the world's most expensive and exquisite caviars. Paddlefish roe is very similar to sevruga caviar, only it's cheaper. Since Caspian Sea sturgeon are rapidly becoming depleted from over-fishing, many people are turning to paddlefish roe as a substitute for caviar.