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Interesting Facts about Cardinal Fish

[Phylum: Chordata] [Class: Actinopterygii] [Order: Kurtiformes] [Family: Apogonidae (ray-finned)]

There are several hundred different species of cardinalfishes (Genera Apogonidae). Most have a lateral (sideways) compressed body and large, bulging eyes.

This section contains fun facts and interesting information about the cardinal fish genus, where to find them, what they eat, and how they reproduce.

Cardinal Fish Habitat and World Distribution

Most cardinalfishes are marine life animals which thrive best in tropical and subtropical waters.

In general, you find them seeking shelter around rocky reefs in shady, shallow environments, such as:

Coral reef structures
Dimly lit outcrops
Lagoons
Dark marine caves

Common areas to find ray-finned cardinalfishes are the Atlantic Ocean, the Indian Ocean, and some regions of the Pacific.

Other distributions of some species, such as the Mediterranean cardinal fish (Apogon Imberbis), congregate in the warmer regions of the eastern Atlantic (e.g. the Gulf of Guinea).

It's not uncommon to find some species in brackish water, and a few others in fresh water, such as the Glossamia aprion (Queensland mouthbrooder).

Characteristics of Cardinalfishes

The ovate (egg-shaped) body of most cardinal marine fish species is easy to identify. In addition, their large head stands out against the short, upturned snout.

A protruding lower jaw, shorter than sling-jaw wrasses, contains rows of tiny villiform teeth. The long pectoral fin stretches down to the start of the anal fin. You should also see signs of emargination in the caudal fin.

Here's the thing:

These ray-finned fishes have large ctenoid scales. It is also common for most cardinal fishes to have two or three dark spots running along the base of the caudal fin.

Almost all Apogonidae are small, especially Kurtiformes. They rarely grow bigger than ten (10) centimetres long.

Nonetheless, the maximum recorded size for the 'King of the Mullets cardinal fish' is fifteen (15) centimetres (6 inches).

What Does the Cardinal Fish Eat?

Having big eyes means this species is content with spending a lot of the daytime hours in dark ravines. It becomes a lot more active in deep water at night to hunt for food.

Cardinal Fish Facts and Species Information with Pictures When the water temperature warms, they tend to stay in a depth range of ten (10) to seventy (70) metres.

But, they will dive deeper to escape the coldness during the winter months - down to two hundred (200) metres.

Marine cardinal fish are carnivorous predators that feed on:

Aquatic crustaceans (e.g. Artemia, brine shrimp)
Euphausiacea (krill)
Marine invertebrates
Opossum shrimps
Tiny organisms (e.g. zooplankton)

Many of the Mediterranean dive sites offer ideal opportunities to catch sightings of this species as they search for food scraps, especially around artificial reef structures.

Types of Cardinal Fish Species

Astrapogon Stellatus (Conchfish)

The symbiotic relationship between A. stellatus and a species of large sea snails (the queen conch) is under threat, mostly due to over-fishing.

This guide contains interesting facts about Astrapogon stellatus conchfish and why alternative refuges with Atrina rigida (the rigid pen shell) could be key for their survival.

Banggai Cardinalfish (Pterapogon kauderni)

This reef-associated species is native to the far eastern end of Central Sulawesi, where it inhabits shallow seagrass beds and coral reef structures near the sheltered coastal zones.

Here's a collection of fun facts about Banggai cardinalfish (Pterapogon kauderni), including where they are found, what they eat, and how these small tropical cardinalfish reproduce.

Blackfin Cardinalfish (Astrapogon puncticulatus)

Astrapogon puncticulatus is one of the small marine cardinals that inhabit the shallow reefs of the western Atlantic, especially southern Florida, the Caribbean Sea, the Gulf of Mexico, and Brazil.

The distinctive features of these particular types of cardinalfish are the bronze body and head colouration, usually stippled with lines and black dots or blotches that radiate from behind the eyes.

Even though they are one of the smaller sized cardinal fish species, growing to about seven (7) centimetres in total body length, they have large eyes that help them see their prey in low lit environments.

Behaviour and Reproduction

Blackfin cardinalfish thrive better around turtle grass (Thalassia testudinum) and near the edges of shallow and sandy reef systems.

It's also common to see them living inside an empty snail shell or the osculum of a large sea sponge, small spaces that they often share with other tropical fishes for refuge.

This nocturnal species spends most of the daylight hiding in reef crevices or branching coral structures. At night, they will emerge to feed on zooplankton and other tiny invertebrates.

Astrapogon puncticulatus is a mouthbrooder, which is a characteristic trait in all cardinalfishes. The males will incubate the fertilised eggs in their mouth until they hatch, which also helps to increase survival rates in their offspring.

Blacktip Cardinalfish (Apogon atradorsatus)

Capricorn Cardinalfish (Apogon capricornis)

Cook's Cardinalfish (Ostorhinchus cookii)

Crown of Thorns Cardinalfish (Siphamia fuscolineata)

Fiveline Cardinalfish (Cheilodipterus quinquelineatus)

Freckled Cardinalfish (Phaeoptyx conklini)

Humpback Cardinalfish (Fibramia lateralis)

Indian Ocean Twospot Cardinalfish (Cheilodipterus novemstriatus)

Longspine Cardinalfish (Apogon doryssa)

Mediterranean Cardinalfish

It's quite easy to identify the ovate (egg-shaped) cardinal red body of Apogon imberbis. The large head is noticeably larger than the short, upturned snout.

This guide contains facts and information about the Mediterranean cardinalfish (also called the King of the Mullets) and how they differ from other ray-finned fishes.

Mouth Almighty (Glossamia aprion)

freshwater cardinalfish

Narrow-lined Cardinalfish (Archamia fucata)

Orbiculate Cardinalfish (Sphaeramia orbicularis)

Pajama Cardinalfish (Sphaeramia nematoptera)

Punctate Cardinalfish (Vincentia punctata)

Ringtailed Cardinalfish (Apogon aureus)

Roughlip Cardinalfish (Apogon robinsi)

Sawcheek Cardinalfish (Apogon quadrisquamatus)

Sea Urchin Cardinalfish (Siphamia tubifer)

Sponge Cardinalfish (Phaeoptyx xenus)

Tiger Cardinalfish (Cheilodipterus macrodon)

Yellowmouth Cardinalfish (Archamia bleekeri)

Cardinal Fish Reproduction

In fact, oviparous reproduction in fishes is commonplace, and parental care is mostly praiseworthy for cardinal fish families. Even so, the males have been known to eat the eggs, often by accident during the courtship ritual.

Internal fertilisation takes place through 'palpitating' movements. This tends to be a weak nuptial dance performed between the fins of the mating partners.

Typically, at least three (3) females will accompany one male in advance of the spawning event. The outcome can turn out to be batches of up to 20,000 eggs.

Male cardinalfish keep the eggs inside its mouth until they hatch. So, until the male expels the eggs, around eight (8) days later, it does not eat any food.

Cardinalfish Predators and Threats

In fact, the threat status for the Mediterranean cardinalfish species in Europe is of 'Least Concern' according to the information on the IUCN website.

But, even though they are not endangered, fishers sometimes use them for bait. Plus, they are also consumed by humans and traded by aquarists for the pet aquarium industry.

Related Information and Help Guides

Pro Tip: The short video [2:21 minutes] presented by 'Deep Marine Scenes' contains even more cardinal fish facts with some fascinating footage of the Banggai cardinalfish (Pterapogon kauderni).