Rare Species Found in Your National Marine Sanctuaries and Monuments
By Rachel Plunkett
February 2025
America’s national marine sanctuaries and monuments protect some of the ocean’s rarest and most fascinating creatures—species that have evolved in unique ways to thrive in these underwater habitats. From deep-sea black corals older than the pyramids, to the elusive and strikingly beautiful masked angelfish (Genicanthus personatus), found only in remote, deep reefs of Hawaii. These marine wonders highlight the importance of conservation efforts that keep our ocean and Great Lakes waters healthy. Here are 11 rare and endemic species that call these protected waters home–either for their entire lives, or for part of their lives—each with its own incredible story.
1. Nautilus (Nautilus samoaensis) - National Marine Sanctuary of American Samoa
The Nautilus samoaensis, a newly identified species of nautilus, was officially described in 2023 and is native to the waters of American Samoa. This ancient mollusk is a distant relative of octopuses and squid. Unlike its cephalopod cousins, the nautilus boasts a remarkable external shell, spiraled and hard, and can have up to 90 tentacles—far more than the eight of an octopus. Found in deep waters around 1,200 feet below the surface, it lives in the remote regions of National Marine Sanctuary of American Samoa. In recent years, researchers from the sanctuary and the National Park of American Samoa, in collaboration with Dr. Peter Ward and Dr. Gregory Barord, have been studying the species’ population and distribution. Their efforts include tracking the nautilus’ movements with a release exercise off the coast of Amalau village to better understand its role in the ecosystem surrounding Tutuila Island.
Nautilus samoaensis is considered rare, though specific population data is limited since it was only just discovered in 2023. Researchers suspect that the Nautilus samoaensis is experiencing similar challenges as other nautilus species, which have seen declining numbers in certain parts of the Pacific due to human activity.
2. Golden Smooth Trunkfish (Lactophrys triqueter) - Flower Garden Banks National Marine Sanctuary
While the smooth trunkfish is commonly found throughout the Caribbean, a rare and striking color morph occurs in the waters of Flower Garden Banks National Marine Sanctuary. Unlike the typical black-and-white smooth trunkfish, this unique morph sports a dazzling gold and silver hue, with pale to bright yellow scales adorned with white spots outlined in black. This golden smooth trunkfish variation is believed to be exclusive to Flower Garden Banks National Marine Sanctuary, making it a special and visually captivating feature of the sanctuary's diverse marine life. The trunkfish, with its distinctive shape and armor-like exterior, is a favorite among divers and researchers alike, who marvel at this natural wonder. The golden morph was first documented in a 1999 study, and it continues to intrigue scientists, as its rarity makes it a symbol of the sanctuary’s rich and diverse ecosystems.
3. Scripps's Murrelet (Synthliboramphus scrippsi) - Channel Islands National Marine Sanctuary
The Scripps’s murrelet is a small, elusive seabird that nests primarily on the rocky cliffs of the Channel Islands, which are surrounded by the waters of Channel Islands National Marine Sanctuary. This rare species spends most of its life at sea, returning to land only to breed. Eighty percent of the U.S. breeding population occurs on the Channel Islands. It is considered one of the rarest seabirds in North America due to its restricted nesting range and susceptibility to introduced predators. Conservation efforts, including habitat restoration and predator removal, have helped stabilize some populations within the Channel Islands, ensuring these unique birds continue to thrive.
4. Laura's limu (Croisettea kalaukapuae) - Papahānaumokuākea National Marine Sanctuary
This newly described deep-reef alga is found only in the remote and pristine waters of Papahānaumokuākea National Marine Sanctuary. Named after Laura Kalaukapu Thompson, a lifelong advocate for conservation and a key figure in Hawaiian cultural preservation, this rare species underscores the monument’s significance in protecting undiscovered marine biodiversity. Its unique structure and ecological role in the deep reefs of the Northwestern Hawaiian Islands make it an important species for future study.
5. Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) - Mallows Bay-Potomac River National Marine Sanctuary
Sturgeons are prehistoric fish that have existed for over 120 million years. The Atlantic sturgeon is among the most endangered species groups in the world, due to habitat loss and harvesting for caviar.
Between 2019 and 2024, the acoustic telemetry receiver in Mallows Bay-Potomac River National Marine Sanctuary recorded over 20,000 detections of 26 different Atlantic sturgeon within the sanctuary. This data suggests that their migratory routes lie within the sanctuary waters, where they spend significant time. Atlantic sturgeon utilize tidal fresh habitats as spawning and essential nursery grounds. The National Marine Fisheries Service has designated much of the Potomac River, including the sanctuary, as critical habitat for this species.
6. Green Lunar Sponge (Latrunculia sp.) - Olympic Coast National Marine Sanctuary
The green lunar sponge (Latrunculia sp.) has specific habitat requirements and is typically found in deep-sea or remote locations that are challenging for researchers to access. This limited distribution contributes to its rarity in the wild. Specimens were collected from Olympic Coast National Marine Sanctuary during a 2020 expedition aboard E/V Nautilus.
Members of this particular marine sponge genus are being investigated for their cancer-fighting properties. Marine sponges contain what are called “bioactive compounds”, which are special chemicals to ward off predators. These compounds have shown promise in medical research, with some exhibiting anti-tumor and antimicrobial properties.
Scientists are particularly interested in how the green lunar sponge's unique chemistry might contribute to future cancer treatments. However, due to the sponge's rarity and the difficulty of obtaining samples, research is still in its early stages. Protecting deep-sea habitats like those within Olympic Coast National Marine Sanctuary is crucial for ensuring that species like the green lunar sponge—and their potential medical benefits—are not lost before they can be fully understood.
7. Black Coral (Distichopathes hickersonae) - Flower Garden Banks National Marine Sanctuary
Distichopathes hickersonae was discovered and described at Elvers Bank in Flower Garden Banks National Marine Sanctuary. This new coral species was identified during remotely operated vehicle explorations associated with sanctuary expansion and is currently considered endemic to the Flower Garden Banks region. Named in honor of former sanctuary research coordinator Emma Hickerson, the coral’s discovery highlights the ongoing role of sanctuary-led research in uncovering deep-sea biodiversity.
8. North Pacific Right Whale (Eubalaena japonica) - Greater Farallones, Cordell Bank, and Monterey Bay National Marine Sanctuaries
One of the rarest whales in the world, the eastern stock of the North Pacific right whale has an estimated population of only 20-40 individuals in the northeastern Pacific. These critically endangered whales were once abundant but were decimated by commercial whaling. Occasional sightings in the waters of Greater Farallones, Cordell Bank, and Monterey Bay National Marine Sanctuaries offer hope for their continued survival. Conservation efforts, including ship strike prevention and habitat protection, remain crucial to preserving this dwindling population.
9. Lake Sturgeon (Acipenser fulvescens) - Great Lakes Sanctuaries
Lake sturgeon, also known as the “gentle giants of the Great lakes,” have a fascinating history in places such as Thunder Bay National Marine Sanctuary. Once abundant, they are now threatened due to overfishing and habitat destruction. In Michigan, an unusual and highly regulated method of harvesting is used, with sturgeon "seasons" sometimes lasting only minutes. Conservation programs such as "Sturgeon in the Classroom", where schools are selected to raise a juvenile sturgeon during the school year, help to educate the public on the species’ ecological and cultural significance, while also meaningfully contributing to conservation efforts.
10. Black Abalone (Haliotis cracherodii) - Monterey Bay National Marine Sanctuary
Once common along the Pacific coast, black abalone populations have plummeted due to overharvesting and withering syndrome, a devastating disease. In the mid-1900s, black abalone abundances were highest south of Monterey, particularly at the Channel Islands off southern California. Listed as endangered under the Endangered Species Act, black abalone are now rare except in the well-protected waters of Monterey Bay National Marine Sanctuary.
Efforts to restore and monitor populations continue, as this species plays a vital role in maintaining the health of kelp forest ecosystems.
11. Masked Angelfish (Genicanthus personatus) - Papahānaumokuākea National Marine Sanctuary
The masked angelfish is a rare and stunning species that is endemic to the Hawaiian Islands, meaning it’s found nowhere else in the world! The species is found exclusively on deep (100-500 feet) reefs of Hawaii, and the highly protected waters of Papahānaumokuākea National Marine Sanctuary are the only place on Earth where they are regularly seen at comfortable scuba depths.
The masked angelfish is one of the most expensive aquarium fish in the world, with a single specimen sometimes exceeding $10,000. The name “masked angelfish” comes from the distinct black mask on the face of juveniles and females. As they mature, males lose the mask and become almost entirely white.
Rachel Plunkett is the content manager and senior writer/editor at NOAA’s Office of National Marine Sanctuaries