Banggai cardinalfish

The Banggai cardinalfish was discovered in 1920 by the Swedish researcher Walter Kaudern and named Pterapogon kauderni in his honor. The first scientific description was published in 1933, after which the species fell into obscurity for a long time. It wasn’t until 1996 that it was, so to speak, rediscovered and initially mistaken for an unknown species. After its presentation at the aquarium fish trade show in Nuremberg, demand for it as an ornamental fish grew rapidly.

Visually, the Banggai cardinalfish is unmistakable: Its silvery-white body features three striking black horizontal bands as well as numerous small white spots on its body and fins. The fins are long and extended, particularly the second dorsal fin and the caudal fin. Males and females look very similar and are almost impossible to tell apart. A reliable distinguishing feature usually becomes apparent only during brood care, when the male’s mouth visibly swells due to the eggs it has taken in. During courtship, the female initiates the courtship display by repeatedly swimming under the male’s caudal fin to signal her readiness to mate. This behavior can last several hours or longer. After the eggs are laid, the male takes them into his mouth and begins mouthbrooding. During this phase, which can last up to one month, he does not eat and turns the eggs regularly.

In most fish species, newly hatched larvae swim freely in open water and are often carried far away by currents, allowing them to colonize new areas. The Banggai cardinalfish lacks this free-swimming larval stage: The juveniles hatch fully developed from the male’s mouth and remain nearby. This explains its unusually small natural range, which is limited to the Banggai Archipelago. This limited range and the intensive aquarium trade threaten the population: the species is critically endangered.