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Microhabitat use of juvenile reef fish and its implications in the use of remote sensing techniques in delineating optimal reef fish habitats
Dissertation Abstract:
Strong habitat and adult reef fish associations have been well established in literature. However, relatively little is known about the habitat associations of juvenile reef fish. In this study, we quantified microhabitat association with juvenile reef fish community structure between reefs that has experienced minimal human intervention (i.e., Ngederrak Reef), and one that has been exposed to high fishing pressure (Bolinao-Anda Reef Complex or BARC). The goal was to look at the role of microhabitat structure in influencing juvenile reef fish diversity and abundance in these two sites, and how microhabitat types can effectively act as surrogate measures of diversity and abundance of juvenile reef fish for possible broad scale assessment applications. The result demonstrated the strong interaction of juvenile reef fish with specific coral reef microhabitats in Ngederrak Reef. However, microhabitat and juvenile reef fish association was weakly manifested in the exploited reefs of BARC. Evidences point to fishing and structural homogenization as the more important drivers that eroded fish-habitat association. The influence of different post-settlement processes also varied between sites and was consistent only in one parameter; juvenile reef fish constantly aggregate more in areas with small refuge spaces. The importance of small refuge spaces to juvenile reef fish was also seen as the primary reason for small-bodied reef fish to aggregate more on structurally complex branching structures (be it dead or alive) in both protected and heavily exploited coral reef areas. The ability of acoustic remote sensing to delineate branching microhabitats elevated its applicability as a broad scale assessment tool for identifying optimal reef fish habitats, at least in protected coral reef areas where habitat association and juvenile reef fish interaction has not been eroded. The results suggest that remotely sensed data could only provide limited biodiversity information at least in an intensely fished, low complexity coral reef area. However, in reefs with dramatically different intensities of fishing, the capability of remote sensing tools to detect areas with rugose hard substrate makes it viable in locating areas with relatively higher fish abundance. Overall, the results have important implications not only in management, but also in modeling the impacts of habitat loss on reef fish community.