Mermaid Island is located on McKeon Flats, a tidal flat formed by the Wosnesenski River as it flows into Neptune Bay, about 13 miles (21 km) northeast of Seldovia and 8 miles (13 km) south-southeast of Homer, Alaska. Neptune Bay is approximately 1.5 miles (2.4 km) wide on the southeastern shore of Kachemak Bay on the Kenai Peninsula. The local name “Mermaid Island” was first reported on charts in the 1940s by the U.S. Coast and Geodetic Survey. The island is connected to the mainland by a recurved spit, which was formed by prevailing wind-generated waves in Kachemak Bay. The mainland and islands in McKeon Flats consist of rocks from the McHugh Complex, a tectonic mélange. This mélange primarily includes weakly metamorphosed siltstone, graywacke, arkose, and conglomerate. These rocks were deposited in a deep ocean trench during the Mississippian to mid-Cretaceous periods, approximately 350 to 100 million years ago. Over time, they were accreted to the continental margin and uplifted due to plate subduction. Repeated glacial advances during the Pleistocene then eroded the bedrock, shaping the present-day landscape.

The islands in McKeon Flats and along the southern shore of Kachemak Bay feature cliffs and rocky headlands that provide nesting habitats for numerous seabird colonies. Pigeon guillemots nest in approximately 30 small colonies of 2 to 15 nests each, with numerous solitary nests scattered along the shore. At least one colony is located in Neptune Bay. Pigeon guillemots, along with their close relatives, the black guillemots, are unique among diving seabirds because they typically forage near the seafloor and within a few kilometers of their nest sites. The pigeon guillemot primarily feeds on benthic prey found near the sea floor, but it also takes some prey from higher in the water column. Its diet mainly consists of fish and other aquatic animals. The fish it consumes include sculpins, sand lance, cod, and capelin. The guillemot also feeds on invertebrates such as shrimp, crabs, polychaete worms, gastropods, bivalves, and squid. Its preferred prey are small fish, particularly the Pacific sand lance, also known as sand eels, which are the most abundant in Kachemak Bay.

The Pacific sand lance is a common schooling fish known for its slender body and pointed snout. It feeds on zooplankton and is often abundant in coastal regions. Notably, sand lances lack pelvic fins and swim bladders. Juvenile sand lances are perhaps the most abundant fish larvae and serve as a major food source for cod, salmon, whales, and other commercially important species. As adults, they are bottom-dwellers that burrow in sandy habitats to avoid tidal currents. They exhibit unusual behavior by alternating between lying buried in the substrate and swimming in well-formed schools. Typically associated with fine gravel and sandy substrates, they inhabit areas up to and including the intertidal zone. In Neptune Bay, they serve as an important food source for diving seabirds, such as guillemots, puffins, auks, terns, and cormorants. Read more here and here. Explore more of Mermaid Island and Neptune Bay here: