Fish diurnal

Dusky Gregory

Stegastes nigricans

Meet the feisty gardener of the coral reef. The Dusky Gregory is a tiny fish with a huge personality, known for fiercely defending its private underwater algae farm from all intruders.

0 Sightings

0 Habitats

Quick Identification

straighten

Size

Typically 9-14 cm (3.5-5.5 inches) in length

palette

Colors

Uniformly dark brownish-grey to purplish-black; some individuals show a faint dark spot at the base of the posterior dorsal fin.

visibility

Key Features

Deep, oval-shaped body profile
Small, terminal mouth used for grazing
Prominent dark spot often visible at the rear of the dorsal fin
Aggressive, territorial swimming patterns

When You’ll See Them

schedule

Activity pattern diurnal

brightness_5

Peak hours 9 AM - 4 PM

calendar_month

Season Year-round

restaurant

Diet Primarily herbivorous; they 'farm' and consume specific types of red and green algae while also eating small invertebrates found within their turf.

park

Habitat Shallow coral reefs, rocky lagoons, and reef flats, typically at depths of 1 to 12 meters.

bar_chart
Loading activity data...

Behavior

The Dusky Gregory is the ultimate underwater gardener. Unlike many reef fish that roam the corals in search of food, this species is highly sedentary and territorial. They establish small patches of 'turf'—lawns of specific filamentous algae—which they meticulously manage. They are famous for 'weeding' their gardens by pulling out unpalatable algae and carrying them outside their territory boundaries to ensure their preferred crops flourish.

These fish are notoriously feisty and will not hesitate to charge at divers, snorkelers, or much larger fish that wander too close to their farm. While they are harmless to humans, their bold, darting movements make them a fascinating subject for observation. They generally live solitary lives within their strictly defined territories, though they may interact during spawning periods.

photo_camera EverydayEarth exclusive

Camera Tips

Capturing the Dusky Gregory requires a waterproof setup, such as an action camera in a dive housing or a specialized underwater trail camera. Because these fish are territorial 'farmers,' you don't need to go looking for them; once you spot a patch of fuzzy, well-kept algae on a shallow reef, you've likely found a Gregory's home. Mount your camera on a weighted tripod or a flexible arm attached to a dead coral outcrop, positioning the lens about 12-24 inches away from the center of their algae patch.

Lighting is crucial for this species because their dark scales can easily appear as a featureless black silhouette. Aim to film in shallow water (under 5 meters) during the middle of the day when the sun is directly overhead. This provides the best color penetration and helps reveal the subtle purplish hues and the defining spot on their dorsal fin. If your camera allows for manual settings, use a high shutter speed to freeze their rapid, jerky movements as they chase away intruders.

Instead of using traditional bait, which might attract unwanted predators, the best 'lure' is the fish's own territorial nature. Set your camera to record in high-definition video or a fast time-lapse mode. If you are patient, you will see the Gregory performing 'maintenance'—picking up debris or unwanted algae and spitting it out away from the garden. For a truly unique shot, placing a small, safe underwater mirror nearby can trigger a 'display' behavior, though this should be done sparingly to avoid stressing the animal.

Ensure your camera is stabilized against surge and current. A shaky camera will often spook the fish or result in unusable footage. Using a wide-angle lens is recommended so you can capture the fish and its entire garden in one frame, providing a clear view of its fascinating agricultural behavior in the context of the wider reef environment.

Similar Species

Species that look similar or are commonly confused with Dusky Gregory.

Cocoa Damselfish

The Cocoa Damselfish typically has a more yellowish tint on the lower body and tail compared to the uniform dark color of the Dusky Gregory.

Pacific Gregory

The Pacific Gregory (Stegastes fasciolatus) often has faint vertical barring and lacks the distinct 'farmer' behavior seen in S. nigricans.

Frequently Asked Questions

Dusky Gregory are strictly diurnal, meaning they are active during daylight hours. They are most busy during the late morning and early afternoon when the sun is strongest, which promotes the growth of the algae they farm.

You don't need food to attract a Dusky Gregory; you simply need to find their 'farm.' Look for a patch of the reef that looks like a manicured lawn of algae. Placing a camera near this territory will naturally capture the fish as it defends and tends to its garden.

They primarily eat filamentous red and green algae. They are unique because they 'weed' their territory to ensure only their favorite types of algae grow, which they then graze on throughout the day.

Yes, they are very common in shallow coral reef environments, often found in water as shallow as one meter, making them easy to spot for snorkelers and shallow-water cameras.

Look for their uniform dark brownish-purple color and a specific dark spot at the very end of their dorsal fin. Their behavior is also a giveaway; if a small dark fish is aggressively 'weeding' a patch of algae or charging at you, it's likely a Dusky Gregory.

Record Dusky Gregory at your habitat

Connect a camera to start building your own species record — AI identifies every visitor automatically.

Join free Identify a photo