A fish known as whiting is being featured at Maine restaurants and retailers in an effort to promote lesser-known and underutilized seafood species. The Gulf of Maine Research Institute’s third Out of the Blue promotional campaign kicks off Friday. During the 10-day promotion, whiting will be the featured product at 21 businesses from Kennebunkport to Bar Harbor. The program earlier this year featured redfish and mackerel to raise public awareness – and demand – for unappreciated seafood species. The research institute, located in Portland, says whiting is a mild whitefish that was historically popular but suffered from overfishing in the 1960s. Whitefish populations are now at healthy levels, but consumer awareness and market prices remain low. For a list of participating restaurants and retailers, people can visit gmri.org/outotheblue.