PORTLAND — A study of Gulf of Maine shallow-water habitats by the federal government finds that sand and gravel habitats are used the most by fish and invertebrate species in the gulf.

The National Oceanic and Atmospheric Administration released the report, which tracked 16 species in different life stages and habitats. The report is intended to identify Gulf of Maine species that use shallow-water habitats that are threatened by humans. It is also meant to be used to enhance the permit application process for activities that could affect the habitats.

The report states that the next most utilized habitats after sand and gravel were mud, eelgrass, macroalgae, boulder, salt marsh channels, and shell beds.