Fish Active during the day

Australian Gregory

Plectroglyphidodon apicalis

iNaturalist Wikipedia

The Australian Gregory is the feisty gardener of the Pacific reefs, famous for its golden-tipped fins and its fearless defense of its private algae patch.

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Quick Identification

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Size

Reaches a maximum length of approximately 15 cm (6 inches), though most individuals are seen around 10 cm (4 inches).

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Colors

Body is typically a dusky brown to grayish-olive with dark-edged scales; the most striking feature is the bright yellow to orange-gold highlights on the tips of the dorsal and anal fins.

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Key Features

Golden-yellow or orange tips on the dorsal and anal fins
Scales with dark margins creating a mesh-like appearance
Deep, oval-shaped body typical of damselfish
Highly aggressive and territorial behavior toward intruders

When You’ll See Them

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Activity pattern Active during the day

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Peak hours 9 AM - 3 PM

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Season Year-round

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Diet Primarily herbivorous; it feeds on filamentous algae that it carefully cultivates and protects within its territory.

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Habitat Shallow coral reefs, rocky reef flats, and surge zones, often in depths of less than 5 metres.

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Where Does the Australian Gregory Live?

The Australian Gregory is a native resident of the Western Pacific Ocean, with its primary stronghold situated along the eastern coast of Australia. Its range extends through the tropical waters of the Great Barrier Reef in Queensland and reaches down into the more temperate rocky reefs of New South Wales. This species has also been documented further afield in the waters surrounding Taiwan and the Loyalty Islands, where it occupies similar shallow-water reef niches.

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3 Countries

2.5M km² Range

Least Concern Conservation

AU Australia Taiwan New Caledonia

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iNaturalist / Verified observation data

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Behavior

The Australian Gregory is best known for its role as a dedicated "algae farmer." This damselfish claims a specific patch of reef or rock, where it meticulously tends to a garden of filamentous algae. It is remarkably territorial, vigorously defending its plot against much larger fish, sea urchins, and even human snorkelers. By chasing away other herbivores, it ensures its food supply remains lush and undisturbed.

In terms of social structure, the Gregory is primarily solitary and spends most of its daylight hours patrolling the boundaries of its territory. It has a complex relationship with its environment, as its "weeding" of the reef can actually influence which types of coral and algae grow in its immediate vicinity. Despite their small size, they are fearless, often darting out from crevices to perform threat displays or rapid nips at perceived threats.

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Camera Tips

Capturing high-quality footage of the Australian Gregory requires an underwater-rated camera or a dedicated reef housing. The secret to success lies in their territorial nature. Unlike many reef fish that flee at the sight of equipment, a Gregory is likely to stand its ground. Look for a patch of rock with a noticeable "carpet" of fine algae; if you see a small brown fish darting at other passersby, you have found a territory. Place your camera on a weighted base or a small tripod about 30 cm from the edge of this patch, ensuring it is secure enough to withstand the surge.

Natural lighting is your best friend when filming underwater. Try to schedule your camera placement during the middle of the day when the sun is highest in the sky. This allows the light to penetrate the shallow water and truly illuminate the golden-yellow tips of the fins, which can otherwise look dull in low light. Because these fish move in quick, erratic bursts, use a camera setting with a high frame rate (at least 60fps) to ensure the AI can clearly identify the fin markings and scale patterns during playback.

You do not need to use bait to attract this species. In fact, adding bait may attract larger predators that will scare the Gregory into its hiding hole. Instead, rely on its curiosity and defensive instincts. The fish will likely approach the camera to inspect the "intruder" in its garden, providing excellent close-up opportunities. Ensure your lens is clean and free of salt spots before deployment, and if possible, use a wide-angle lens to capture the fish's interactions with other reef inhabitants that wander too close to its borders.

Frequently Asked Questions

Australian Gregory are strictly diurnal, meaning they are active during daylight hours. They are most visible from mid-morning to late afternoon when they are busy grazing on their algae patches and defending their territory from intruders.

You don't need food to attract them! Simply place your underwater camera near a patch of reef that looks like it is being 'farmed' (areas with short, lush algae). The fish's territorial nature will naturally bring it close to the lens to investigate the new object.

They are primarily herbivores. They eat filamentous algae which they grow in their own territories, often 'weeding' out unpalatable types of algae to ensure their preferred food source thrives.

They are common in coastal waters adjacent to suburban areas in Queensland and New South Wales, particularly around rocky headlands and in shallow tide pools accessible to snorkelers.

Look for the distinctive yellow or orange tips on the top of the dorsal fin and the anal fin. While many damselfish are brown, the 'yellow-tip' feature combined with their aggressive 'farming' behavior is a key identifier for this species.

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