Population status and microhabitat preferences of endemic Banggai cardinalfish (Pterapogon kauderni) in the introduced habitat in Kendari Bay, Indonesia

Endemic Banggai cardinalfish has been found in several regions of Indonesia as an introduced species, including Kendari, Southeast Sulawesi. Observation on Banggai cardinalfish in Kendari Bay waters was carried out from late March to early April 2019 to obtain data on population and microhabitat preferences of Banggai cardinalfish in this location. The data were collected by scuba diving using a modified Belt Transect method, with 3 replicate transects (20x5 m) at each station. Observations of abundance, habitat and microhabitat preferences of Banggai cardinalfish were carried out in each belt transect. The fish was classified into 3 sizes based on standard length (SL): post-larval stage, juvenile, and adult. As supporting data of environmental, several parameters of physic and chemical were also measured at each location. The result shows that Banggai cardinalfish populations were found in all five locations at varying densities. 589 individuals of fish observed during the survey at five stations, consisting of 1.53% pot-larvae stages (9 individuals), 38.88% juveniles (229 individuals) and 59.59% adults (351 individuals). The density was ranged 0.31-2.41 ind m⁻², which the lowest was in Station I (North part of Bokori Island), and the highest was in Station II (West part of Bokori Island). The maximum density for post-larvae stages was found at Station V (0.09 ind m⁻²), for juveniles at Station II (1.42 ind m⁻²) and for adults at Station IV (1.04 ind m⁻²). The majority (71.82%) of the Banggai cardinalfish were associated with black sea urchins (Diadema spp.), others associated with seagrass (11.71%), coral branching (9.51%), sea anemones (5.43%) and mushroom coral (1.53%). Juveniles and adults were generally found to be associated with sea urchin, while all post-larvae stages were associated with Heliofungia actiniformis. The results show that the Banggai cardinalfish has been able to adapt and establish resident populations in Kendari Bay water.