Banggai cardinalfish

Appearance

This species grows up to 8 centimetres total length. It has a distinctive contrasting pattern of black and light bars with white spots. This species is easily differentiated from all other cardinalfish by its tasseled first dorsal fin, elongate anal and second dorsal fin rays, deeply forked caudal fin, and color pattern consisting of three black bars across the head and body and prominent black anterior edges on the anal and second dorsal fin. Males can be differentiated from females by a conspicuous enlarged oral cavity, which is apparent only when they are brooding.

Distribution

This species is restricted to the Banggai Islands of Indonesia.This species has an extremely limited geographic range and small total population size . The Banggai cardinalfish is composed of isolated populations concentrated around the shallows of 17 large and 10 small islands within the Banggai Archipelago. A small population also occurs off Central Sulawesi, within Luwuk harbor. One additional population has become established in the Lembeh Strait , 400 km north of the natural area of the species distribution, following introduction by aquarium fish traders in 2000.

Based on survey between 1994 to 2004, there were 159 locations of the cardinal fish in more than 50 islands, but decreased significantly to only 10 locations in June 2010 with the most locations were Teopot, Tinakin Laut and Bone Baru areas with 1500, 1,205 and 1,005 fish per 500 meter square, respectively. Over catching and less of Diadema setosum were predicted as the cause of decreasing cardinal fish population. Diadema setosum is catched for consumption and prey of fishing, wether Diadema setosum is guardian for cardinal fish from predators.

Habitat

The Banggai cardinalfish is the only representative of the family that is diurnal. It is a demersal tropical marine fish that forms stable groups of about 9 individuals in shallow water, being most common at 1.5–2.5 m depth. The species inhabits a variety of shallow habitats, including coral reefs, seagrass beds, and open areas of sand and rubble. It is most common in calm habitats on the protected side of larger islands. It is often found associated with the seagrass ''Enhalus acoroides'' and the long spined sea urchin ''Diadema setosum''. It occurs among various living benthic substrates such as sea urchins, sea anemones, and branching corals; young fish are most commonly associated with sea anemone, while juveniles and adults occur most frequently among long-spined sea urchins and branching corals, as well as sea stars, hydrozoans, and mangrove prop roots. Individuals of 2 to 60 hover directly above the urchins, with the younger ones about 2–3 cm SL staying closer to the urchins. The fish retreat among the spines when threatened. Individual fish exhibit well-defined homing behaviour and return to the original location of their group when disturbed. Banggai cardinalfish often coexist with various anemonefish and anemone shrimp when sheltering in anemones and corals; when found among sea urchin spines, it associates with several other genera of cardinalfish. Following removal of the fish by aquarium collectors, the
abundance of associated invertebrates has been shown to decline.

These fish are an opportunistic species that feeds during the day, unlike all other representatives of this family. Diet composition is similar between size classes, including planktonic, demersal, and benthic organisms. Copepods constitute a bulk of their diet. It serves as an important food source for several species of lionfish , the grouper ''Epinephelus merra'', a crocodilefish , a moray eel , a stonefish , and the sea snake ''Laticauda colubrina''.

The Banggai cardinalfish is a paternal mouthbrooder. Females play an active role in courtship and pair formation, which occurs a few hours up to a few days before spawning; mating pairs establish spawning territories several meters away from the main group and vigorously defend these territories. The large eggs are about 2.5 millimetres in diameter, with the young remaining within the mouth cavity for undetermined period after hatching. Unlike many other species of marine fish, the Banggai cardinalfish lacks a planktonic stage in its life history. The species has a short life span and small spawn size , although it can potentially reproduce several times per year .