Got a photo? Identify fish instantly with the Fishby app.
Open the appDescription
The Cortez Damselfish (Stegastes rectifraenum) is a small, territorial marine fish belonging to the family Pomacentridae. It is a common inhabitant of rocky reefs and coral formations in the Eastern Pacific, particularly in the Gulf of California. Known for its aggressive territorial behavior, especially during breeding, it plays a significant role in its ecosystem by farming algae patches.
Physical Characteristics
- Body shape
- compressed
- Coloration
- Adults are typically dark brown to black, often with a yellowish or orange tint on the caudal fin and sometimes on the posterior body. Juveniles are often brighter, displaying iridescent blue spots or lines, particularly on the head and dorsal fin, which fade with age. Some individuals may exhibit a pale bar behind the pectoral fin.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Dark body coloration, often with a yellowish caudal fin., Robust, compressed body., Small, terminal mouth., Prominent scales.
- Dorsal fin
- Single dorsal fin with 12 spines and 14-16 soft rays.
- Tail fin
- Forked or emarginate caudal fin, often yellowish.
- Pectoral fin
- Rounded pectoral fins.
- Distinctive fins
- Anal fin with 2 spines and 12-14 soft rays. Pelvic fins are thoracic.
Identification Tips
Coloration
Look for the dark brown to black body with a distinct yellowish or orange caudal fin in adults. Juveniles have iridescent blue markings.
Body Shape
Its deep, compressed body is characteristic of damselfishes.
Behavior
Observe its highly territorial nature, often seen aggressively defending a small patch of reef or algae.
Habitat
- Water type
- saltwater
- Depth
- Typically found in shallow waters from 1 to 20 meters (3 to 65 feet), occasionally deeper.
- Environment
- Rocky reefs, coral reefs, and rubble zones. They are highly territorial and often associated with specific rock formations or algal patches that they 'farm'.
- Geographic range
- Eastern Pacific Ocean, from the Gulf of California (Baja California Sur, Mexico) south to Peru, including offshore islands such as the Revillagigedo Islands and Clipperton Island.
Aquarium Information
- Care level: intermediate
- Temperament: aggressive
- Diet: omnivore
- Minimum tank size: 30 gallons
- Temperature: 72-78°F (22-26°C)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Not suitable for peaceful community tanks. Best kept singly or with very robust, larger fish. Will aggressively defend its territory against similar-sized or smaller fish.
- Special requirements: Requires ample rockwork for territories and hiding spots. A well-established tank with good algal growth is beneficial as they graze on algae. Provide a varied diet including spirulina, marine algae, and meaty foods.
Wild Information
- Conservation status: least concern
- Seasonality: Breeds year-round, with peak activity during warmer months. Behavior is consistent throughout the year, though territoriality intensifies during spawning.
- Market price: Low
- Commercial importance: low
- Taste: Not typically consumed due to small size and bony nature.
- Texture: Not typically consumed.
- Nutritional value: Not typically consumed.
Key Facts
Algae Farmerbehavior
Cortez Damselfish are known as 'algae farmers.' They actively cultivate and defend small patches of filamentous algae, which serve as their primary food source. They will aggressively chase away other herbivores that attempt to graze on their patch.
Territorialitybehavior
This species is exceptionally territorial, especially males during breeding season. They will defend their chosen patch of reef against intruders much larger than themselves, including divers.
Juvenile Colorationinteresting
Juvenile Cortez Damselfish exhibit striking iridescent blue spots and lines, particularly on their head and dorsal fin, which gradually fade as they mature into their darker adult coloration.
Ecological Rolebehavior
By maintaining their algal gardens, Cortez Damselfish influence the community structure of benthic algae and invertebrates on rocky reefs, impacting nutrient cycling and primary productivity.
Safety Information
Handle with care- Safety level: caution
- Venomous: No
- Edibility: not recommended
- Handling notes: While not venomous, Cortez Damselfish can deliver a painful bite if handled due to their strong jaws and sharp teeth. Their dorsal spines are also sharp and can cause minor punctures. Handle with care, preferably using gloves or a net.
Similar Species
Giant Damselfish
Microspathodon dorsalis
The Giant Damselfish is significantly larger (up to 30 cm) and has a more robust body. While also dark, it lacks the distinct yellowish caudal fin of the Cortez Damselfish and has a more pronounced hump on its forehead as an adult.
Panama Sergeant Major
Abudefduf concolor
The Panama Sergeant Major has a more silvery-grey body with distinct vertical black bars, a feature absent in the Cortez Damselfish. It also tends to be less solitary and territorial than Stegastes rectifraenum.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Perciformes
- Family
- Pomacentridae
- Genus
- Stegastes
- Species
- rectifraenum
Explore Cortez Damselfish
Identify fish anywhere
Free on iOS, Android, and Web. Photo identification, full species details, and more.