This animation shows the movement of tagged Nassau grouper around the island of Little Cayman in the days surrounding the full moon of January 2006. Each of the colored squares represents a different tagged individual. Red arrows show direction of movement between different hydrophones (listening stations that can detect tags). Nassau grouper currently aggregate to spawn on the western end of the island's shelf edge (the left side of the animation). Decades ago, the fish aggregated on the far eastern edge of the island's shelf (the right side of the animation). Notice that while fish visit the old aggregation site, during nights of peak spawning all tagged fish are present on the current western aggregation site. The sigmoidal graph on the top of the animation shows lunar phase, with the peaks of the blue line indicating full moon, while the troughs indicate new moon. The red line indicates "current" time as the animation proceeds. Note that in 2006, peak spawning happened appoximately 6 days after the full moon in January.
This research is part of the REEF Grouper Moon Project, in collaboration with the Cayman Island Department of Environment. The project lead scientist is Dr. Brice Semmens, Scripps Institution of Oceanography.
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