Fishes Active at night

Longspine Squirrelfish

Holocentrus rufus

iNaturalist Wikipedia

A nocturnal sentinel of the Caribbean reefs, the Longspine Squirrelfish is easily recognized by its massive eyes and vibrant golden-red stripes. This vocal reef-dweller uses unique 'grunts' to guard its home and navigate the night.

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Quick Identification

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Size

Typically 18 cm (7 inches) in length, with maximum recorded sizes reaching up to 35 cm (14 inches).

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Colors

Silvery-red base color with prominent horizontal orange-gold stripes along the body. The dorsal fin spines are often tipped with white.

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Key Features

Extraordinarily large black eyes adapted for low light
Long, sharp third spine on the anal fin
Bright silvery-red body with golden longitudinal stripes
Deeply forked tail fin

When You’ll See Them

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Activity pattern Active at night

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Peak hours 8 PM - 4 AM

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Season Year-round

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Diet Carnivorous zoobenthos feeder, primarily consuming crabs, shrimp, marine worms, and small gastropods found on or near the seafloor.

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Habitat Tropical coral reefs, rocky sea floors, and shallow coastal caves, typically at depths between 1 and 35 meters.

public Geographic range

Where Does the Longspine Squirrelfish Live?

Native to the warm waters of the Western Atlantic Ocean, the Longspine Squirrelfish is a quintessential inhabitant of the Caribbean basin. Its range stretches from the coastal waters of North Carolina and Bermuda in the north, extending through the Florida Keys and the Gulf of Mexico, and reaching as far south as the coast of Brazil. These fish are most abundant in the clear, reef-rich environments of the West Indies and the Bahamas, where stable water temperatures support their year-round activity.

Basemap © OpenStreetMap contributors

10 Countries

15.5M km² Range

Least Concern Conservation

US United States Bahamas MX Mexico BR Brazil Cuba Jamaica Dominican Republic BZ Belize PA Panama VE Venezuela

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iNaturalist / Verified observation data

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Behavior

The Longspine Squirrelfish is a nocturnal specialist, spending its daylight hours tucked away in the shadows of coral crevices or rocky overhangs. While they appear shy during the day, they are intensely territorial and will aggressively defend their chosen 'hole' from intruders. They are famous among divers for their vocalizations; they produce distinct 'grunts' and 'staccato' sounds by vibrating their swim bladder using specialized muscles. These sounds serve as warnings to rivals and can even be used to intimidate predators like moray eels.

As the sun sets, these fish emerge from their hiding spots to hunt. Despite their small size, they are bold foragers, moving across the reef flat to find prey. Their social structure is loosely organized around high-quality shelter sites, and while they may gather in groups to harass a common threat, they are generally solitary when it comes to defending their personal space. Their interaction with humans is usually passive, though they are a popular sight for snorkelers and are occasionally kept in large saltwater aquaria.

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Camera Tips

To capture the Longspine Squirrelfish on a backyard or dock-mounted camera, you will need a waterproof housing or a specialized underwater trail camera. Because these fish are nocturnal, your camera's infrared (IR) or low-light capabilities are critical. Position your camera near the entrance of a rock pile, a seawall crevice, or a coral head about 1 to 2 feet off the seabed. Angling the camera slightly upward can help capture the silvery-red reflection of their scales when they emerge at dusk.

While traditional 'baiting' is often discouraged in open reefs, if you are monitoring a private dock area, subtle lures like a perforated container of crushed shrimp can draw them into the camera's field of view. Be aware that these fish are attracted to structure; if your 'backyard' is a canal or waterfront property, placing some safe, submerged rocky debris within view of your lens will almost certainly attract a resident squirrelfish looking for a territory to defend.

Set your camera to video mode rather than still photos to capture their unique 'hovering' swimming style and potential vocalizations. If your camera has a sensitive internal microphone, you might even record their defensive grunts. Ensure your PIR (passive infrared) sensors are tuned for underwater movement, or use time-lapse mode during the first four hours after sunset, which is their peak foraging window.

Similar Species

Species that look similar or are commonly confused with Longspine Squirrelfish.

Squirrelfish

Very similar but lacks the elongated third anal spine and the distinct white tips on the dorsal fin spines.

Blackbar Soldierfish

Has a much deeper red color and a vertical black bar behind the gill cover, lacking the horizontal gold stripes.

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Frequently Asked Questions

Longspine Squirrelfish are strictly nocturnal. They spend their days hiding in reef crevices and become most active shortly after sunset, hunting for small crustaceans until dawn.

Provide 'structure' like rock piles or submerged pipes near your camera. They are highly territorial and will move into any suitable crevice that offers protection from daytime predators.

They are carnivorous bottom-feeders that primarily eat crabs, shrimp, and other small invertebrates (zoobenthos) that emerge on the reef at night.

Yes, in tropical regions like Florida and the Caribbean, they are very common around residential docks, seawalls, and riprap jetties that provide plenty of hiding spots.

The Longspine Squirrelfish (Holocentrus rufus) has a much longer third spine on its anal fin and typically features white tips on its dorsal spines, which are less prominent in the Common Squirrelfish.

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