PORTLAND — Atlantic mackerel is being featured on menus at Maine restaurants as part of a campaign that aims to promote underutilized seafood species found in the Gulf of Maine.

Beginning Friday, about 20 participating restaurants and retailers will promote mackerel for 10 days as part of the Gulf of Maine Research Institute’s Out of the Blue campaign, now in its second year.

The campaign last month featured redfish. Dogfish, whiting and pollock are slated to be featured in additional promotions this summer and fall.

Mackerel is considered one of the healthiest fish for human consumption, but there is little consumer demand for it.

For a list of participating restaurants and retailers, people can visit www.gmri.org.