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hawaiian gregoryHawaiian Gregory
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Osteichthys Family: Pomacentridae Genus: Stergastes Species: marginatus
Scientific name: Stergastes marginatus
Common name: Hawaiian Gregory
Hawaiian name: none

The Hawaiian Gregory (Stergastes marginatus) is an endemic species only found in Hawaii. It is closely related to the Pacific Gregory (S. fasciolatus) that has a huge range from Africa across the Indian Ocean as far as Easter Island.

Hawaiian Gregory’s are a scruffy-looking, brownish-gray damselfish sporting a bright yellow iris. They live in shallow, rocky areas in moderately protected areas. Each Gregory maintains a garden of delectable algae cultivated by weeding out unpalatable species. They also consume small animals that feed on their pastures of algae. Gregory’s will defend their territory vigorously from neighbors and attack other herbivorous fish that stray too close. These damselfish are fiercely territorial. Pound for pound they are, perhaps, one of the most aggressive fishes on Hawaii’s Turtle Reef. The area they defend is large enough for their means, (usually around 10 square feet) and includes a refuge into which they retreat when approached by predators. Like most damselfish, the male clears part of its territory of algae for its nest site. It fiercely guards it from other males and herbivores in general, while readily entertaining passing females.

Gregorys are considered to be a “keystone” species because they alter the structure of the reefs they inhabit. There is also evidence that the Gregorys increase the biodiversity and productivity of the areas in which they live.  Because Gregorys are so vigorous in their defense of territory certain species of algae and corals escape the depredation of individual herbivorous and coralivorous fishes. Grazing feeding parties and mixed schools, on the other hand, can overwhelm the Gregorys’ territorial defenses.

[Back to Reef Species Guide]