An integrative investigation of larval behavior using a coral reef fish
Majoris, John Edwin
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A primary goal of marine ecology is to understand the physical and biological mechanisms that drive patterns of larval dispersal and population connectivity. The larvae of many marine organisms develop in the pelagic environment before settling on benthic habitat. Early efforts to predict dispersal patterns assumed that larvae are passive particles dispersed by currents for 10s to 100s of kilometers (km). However, recent studies using parentage analyses to observe dispersal patterns reveal that peak dispersal occurs within 1 – 2 km, and declines exponentially with increasing distance from the natal reef. This gap between predicted and observed dispersal patterns suggests that other factors, such as larval behavior, may play an important role in shaping patterns of dispersal. However, due to challenges associated with obtaining larvae early in development, there is little information on the ontogeny of behavior from hatching through settlement. In this dissertation, I begin to address these challenges by developing a protocol for rearing the larvae of two species of sponge-dwelling neon gobies, Elacatinus lori and E. colini. Using lab-reared specimens, I provide the first description of larval development for both species. Then, I investigate the ontogeny of swimming ability in larvae of E. lori, E. colini and the model species Amphiprion percula. Remarkably, A. percula were capable of swimming twice as fast and three orders of magnitude longer than E. lori near settlement. Relating swimming speed to published dispersal patterns for E. lori, A. percula and another species Plectropomus leopardus, I show there is a positive association between swimming speed and the median and maximum dispersal distance. This finding suggests that swimming abilities may influence the extent of long distance dispersal. Finally, I investigate the role of habitat preferences and post-settlement persistence in establishing the distribution of E. lori settlers on sponge habitat. I demonstrate that E. lori settlers are more abundant, persist longer, and prefer to settle on large Aplysina fistularis, suggesting that settling E. lori choose sponge habitats that confer the highest relative fitness. This dissertation indicates the importance of larval and settler behaviors in determining the dispersal patterns and distribution of fishes on coral reefs.