| ORIENTATION BEHAVIOR IN FISH LARVAE: A MISSING PIECE TO HJORTS CRITICAL PERIOD HYPOTHESIS |
| STAATERMAN, ERICA; Paris, Claire B.; & Helgers, Judith
University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami FL 33149, USA.
estaaterman@rsmas.miami.edu, cparis@rsmas.miami.edu, judithhelgers@gmail.com
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| Larval reef fish possess considerable swimming and sensory abilities, which could enable navigation towards settlement habitat from the open ocean. Due to their small size and relatively low survival, tagging individual larvae is not a viable option, but numerical modeling studies have proven useful for understanding the role of orientation throughout ontogeny. Here we combined the theoretical framework of the biased correlated random walk model with a very high resolution three-dimensional coupled biophysical model to investigate the role of orientation behavior in fish larvae. Virtual larvae of the bicolor damselfish (Stegastes partitus) were released daily during their peak spawning period in the Florida Keys Reef Tract, a region of complex eddy fields bounded by the strong Florida Current. The larvae began orientation behavior either immediately after hatching or during flexion, increased their swimming speed during ontogeny, and settled on reefs within a flexible window of 24 and 32 days pelagic larval duration. Only larvae that were within a maximum detection distance from the reefs were allowed to orient, otherwise their movement was limited to vertical migration and passive horizontal advection. Larvae that began to orient early were more likely to reach reef habitat than those that oriented late, and the most successful larvae possessed the largest maximum detection distance, implying that the use of large-scale cues increases survival. Orientation behavior also increased the number of larvae that settled near their home reef, providing evidence that orientation is a mechanism driving self-recruitment in reef fish. This study demonstrates that despite low swimming abilities of the earliest stages, orientation during this critical period would have remarkable demographic consequences.
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