Kajian konektivitas habitat ikan terumbu ontogeni menggunakan pemodelan geospasial di perairan Kepulauan Seribu

Abstract

Reef fish communities exist at spatially distributed populations that correspond to various reefscape elements, for example landscape connectedness, the amount of habitat, and configuration of habitat patches. One type of connection exists between reef fish population is related with ontogenetic shift, in where juveniles use different types of habitat compare to adults. Supported by appropriate accuracy setting, integrated remote sensing technology can provide functional tools for informing complex landscape of reef habitats as well as reef geomorphology, one aspect still lacking of comprehensive studies in the Indonesian seascape. A total of 17 reef sites and 14 seagrass sites were assessed to gather basic information on reef fish community structure and potential structural connectivity facilitating ontogenetic shifts between different reef habitats in Kepulauan Seribu. Quickbird imagery analysis resulted in 13 thematic habitat classes and 8 geomorphological classes, with fine to excellent accuracy. Coupled with acoustic dataset, complex details of reef geomorphology at deeper depth (>18 meter) with 13 thematic classes were obtained from Benthic Terrain Modeler revealing structures which may facilitate reef fish spawning process (i.e.: Rock outcrop highs, narrow ridges/Ronr; Scarp, cliff; or small local depression on slope/Scos; Local ridges, boulders, pinnacles on broad flats/Lopb; Local ridges, boulders, pinnacles in depression/Lopd; Local ridges, boulders, pinnacles on slopes/Lops; and Crevices, narrow gullies over elevated terrain/Cret). Ontogenetic connectivity was analyzed structurally by reviewing spatial characteristics of the physical structure of the coastal environment as resulted from remote sensing imagery, and potentially by several scenarios of reef fish larval dispersal. Using spatial and statistic analysis, the results indicated that benthic habitat configuration metrics at several spatial scales (Perimeter:Area of habitat patch-P:A*, habitat extent-A*, and nearest distance between two ontogenetic habitats-JO*) may serve as proxies for examining ontogenetic connectivity and reef fish community structure. Juvenile fish species richness exhibit marginal association with P:A of seagrass patch at 250 m spatial extent (PAL250); while association between showing-spawn-cues adult reef fish is moderately strong at every spatial scale with reef area (AT*). Despite the seasonal variability of potential ontogenic connectivity, larval dispersal simulation revealed that several sites around Panggang Island provide the highest potential to be linked with seagrass patches, thus facilitating ontogenetic connectivity between spawning habitats at outer reefs to nursery habitats at inner reefs.