Ornate Bichir

Ornate bichir（Polypterus ornatipinnis）。（圖片來源：lapradei，採用 CC BY-NC 4.0 授權）

The ornate bichir (Polypterus ornatipinnis) is a member of the class Actinopterygii, order Polypteriformes, and family Polypteridae. It is a predatory fish commonly found in the aquarium trade. Because of its extremely primitive appearance and body structure that differs markedly from most teleost fishes, it is often referred to in the aquarium market as a “dinosaur fish.” In Chinese markets it is commonly called the “large-spotted dinosaur fish,” while in English it is generally known as the Ornate bichir.

Morphology

Externally, the ornate bichir possesses the defining feature of the family Polypteridae: multiple separate dorsal finlets. These small dorsal fin spines are one of the most important diagnostic traits used to identify bichirs. In this species, the dorsal finlets typically number between 9 and 11, while the anal fin contains 14–15 soft rays. The predorsal scale count ranges from 58 to 65. The upper and lower jaws are approximately equal in length, which is also an important characteristic for species identification.

In addition, unlike most modern ray-finned fishes, the ornate bichir retains many ancestral features of early actinopterygians. One example is the presence of distinctive ganoid scales. These scales consist of several layers, including a heavily mineralized outer ganoine layer, a dentine-like cosmine layer, a vascular layer containing internal cavities, and an inner isopedine layer composed of parallel bony plates.

Because their native habitats are densely vegetated swamp environments, bichirs have evolved a cylindrical body and flattened head that allow them to move effectively through structurally complex benthic habitats. To survive in wetlands and lakes that experience pronounced wet and dry seasons, these fishes have also independently evolved respiratory structures resembling those of lobe-finned fishes, including spiracles and a lung-like swim bladder. These adaptations allow them to obtain atmospheric oxygen and even leave drying pools temporarily during drought periods in search of more suitable aquatic habitats.

In terms of coloration, adult ornate bichirs display striking patterns. Their bodies typically have a dark background covered with numerous pale or golden spots and blotches, giving them a highly ornate appearance. In size, the species is considered a medium-to-large predatory fish. The maximum standard length generally reaches about 50–60 cm, making it one of the larger members of the Polypteridae.

Ornate bichir in an aquarium（圖片來源：Logan McGuire-Warden，採用 CC BY 4.0 授權。）

During early development, bichirs differ markedly from most fishes. Juveniles possess distinctive external gills, giving them an appearance reminiscent of amphibian larvae. The evolutionary reason for this unusual trait is still not fully understood. However, it is known that these external gills gradually regress and disappear as the fish grows.

Native Range and Habitat

The ornate bichir is distributed in Africa, including the Congo River basin, Lake Tanganyika, and the Lake Rukwa drainage system. It inhabits streams, swamps, and slow-moving waters with dense vegetation. These fishes primarily occur in freshwater rivers and sluggish aquatic environments. As ambush predators, ornate bichirs prefer habitats with slow current, shallow areas rich in vegetation, and substrates composed of mud and sand. When dissolved oxygen levels decline, they can supplement respiration by breathing atmospheric oxygen using their lung-like organs.

Aquarium Conditions

The ornate bichir is a large predatory fish and is generally recommended to be kept singly. It should not be housed with small fish or other aggressive large predators. If mixed species aquaria are desired, it is preferable to keep them with large, relatively peaceful fish.

Aquarium size should be designed according to the adult body length of the fish. A single individual typically requires a tank of at least 300–500 liters, with a minimum length of approximately 120 cm, allowing adequate space for turning and movement. If multiple individuals are kept together, a significantly larger tank is necessary.

One important point is that bichirs are extremely capable jumpers. When designing an aquarium system, a secure yet ventilated lid should be installed to prevent the fish from escaping the tank due to stress or while surfacing to breathe.

In terms of habitat design, bichirs are classic ambush predators that prefer shaded or sheltered environments. Aquarium setups should therefore include driftwood, caves, dense vegetation, or floating plants to create hiding spaces. The substrate should consist of sand or fine gravel. Strong direct lighting should be avoided, as it may induce stress.

Water conditions should be maintained at temperatures between 24–28°C, with water chemistry ranging from neutral to slightly acidic or slightly alkaline (approximately pH 6.0–8.0). Gentle water flow or mild filtration circulation is recommended; strong currents should be avoided. Because bichirs are benthic carnivores that generate significant food debris and organic waste, relatively frequent water changes are required. Typically, 20–30% of the water should be replaced weekly, or adjusted according to water quality conditions. Filtration systems should combine efficient biological filtration with mechanical filtration.

Feeding Conditions

Bichirs are bottom-dwelling carnivores. In the wild they primarily feed on small fish, crustaceans, earthworms, insects, and aquatic invertebrates. In aquaria they readily accept sinking carnivore pellets or frozen foods such as bloodworms, shrimp, and fish flesh. A varied diet is recommended to maintain balanced nutrition.

Adult individuals are usually fed once per day or every other day, depending on their activity level and appetite. Juveniles require more frequent feeding, typically once or twice per day. Feeding is best performed under dim lighting conditions or during dusk or nighttime, as bichirs are generally nocturnal and feed more actively in low-light environments.

Breeding Conditions

Bichirs are egg-laying fishes that scatter adhesive eggs, which attach to aquatic plants or spawning substrates. The number of eggs produced per spawning event may range from several dozen to several hundred depending on the species. Fertilization occurs externally. During spawning, the male wraps around the female and releases sperm as the eggs are expelled.

The incubation period typically lasts about 3–7 days, depending on temperature. Newly hatched larvae initially feed on planktonic or very small benthic prey, and during early development they may possess external gills.

There are historical records of successful captive breeding of ornate bichirs by early aquarists, including Walter Armbrust in the 1960s. In the modern aquarium trade, individuals bred in Indonesia are also available, although not all specimens are captive-bred. To encourage spawning in captivity, providing abundant plants or spawning mops, maintaining stable water quality, and simulating seasonal changes such as fluctuations in temperature or water level may help trigger reproductive behavior. During the incubation period, antifungal treatment (for example with methylene blue) may be used when necessary, and larvae should be provided with small live foods such as protozoans, micro-rotifers, or newly hatched brine shrimp.

Preventing Invasive Spread

The ornate bichir is native to Africa and is a highly adaptable carnivorous fish. If released into non-native environments, abandoned individuals can easily become invasive species and threaten local ecosystems. They may prey on the eggs and juveniles of native fish and compete with local species for food resources, potentially disrupting native fish populations.

Aquarists must therefore follow the principle of “no abandonment and no release.” Under no circumstances should bichirs be released into natural waters. If an owner can no longer keep the fish, it should be transferred to another aquarist or rehomed through an aquarium facility that is willing to accept it.

Author: Rodrigo

References:

1. Boulenger, G. A. (1902). Additions à la faune ichthyologique du bassin du Congo. Matériaux pour la faune du Congo. Annales du Musée du Congo (Sér. Zool.), 2(fasc. 2), 19–57.

2. Froese, R., & Pauly, D. (Eds.). (2025). Polypterus ornatipinnis Boulenger, 1902. FishBase. Retrieved September 13, 2025, from https://www.fishbase.se/summary/Polypterus-ornatipinnis.html

3. IUCN. (2009). Polypterus ornatipinnis: The IUCN Red List of Threatened Species 2009: e.T182062A7807150. Retrieved September 13, 2025, from https://www.iucnredlist.org/species/182062/7807150

4. Moritz, T., & Britz, R. (2019). Revision of the extant Polypteridae (Actinopterygii: Cladistia). Verlag Dr. Friedrich Pfeil. (Species-level taxonomic revision of Polypteridae; useful for modern taxonomic context and valid species list).

5. Evans, S. (n.d.). Polypterus ornatipinnis (Ornate bichir). Polypterus.info. Retrieved September 13, 2025, from https://www.polypterus.info/p_ornatipinnis.htm

6. GBIF Secretariat. (2025). Polypterus ornatipinnis Boulenger, 1902. GBIF Backbone Taxonomy. Retrieved September 13, 2025, from https://www.gbif.org/species/2346593