Sunday evening marked the first evening that we observed the Nassau grouper spawning at the aggregation site! It was an incredible site to witness. The groupers would shoot upward into the water column as they were spawning, like fireworks.  As the female went up into the water column swimming to release her eggs, several male groupers would follow, swimming in spirals around her. We also had several Caribbean reef sharks swim through the Nassau grouper aggregation site, which was an exciting way to watch the food web in action with the incredible apex predators amongst the groupers.

The day of spawning, we noticed several things on the morning dive that were clues the spawning might  start later that evening. We noticed that the female groupers bellies were swollen with eggs, and many more of the fish were in the bi-color or dark phase. There were very few fish in the normal or barred color phase. We also noticed changes in the current and the presence of other fish that we don’t typically see on the reef either. For example, two of the divers saw a school of blackfin tuna near the surface! This species is typically found far offshore in the blue ocean, not on the reef. Researchers think that the Nassau grouper possibly chose this particular spot off Little Cayman because the currents tend to push inward and down, to possibly keep the Nassau grouper eggs close to their home reef in Little Cayman, instead of using the currents to get some place else, like sea turtle hatchlings do. The researchers have special scientific instruments near the aggregation site to measure the currents and how the currents change. There are many questions about the Nassau grouper that the Grouper Moon Project team have and are researching. This is yet another reason why it’s important to stay curious and always ask questions about the world around you. Do you have any questions for the Grouper Moon Project team? If so, post them as a comment on the blog, and the team will try to answer them for you.