Shark 'dandruff' reveals vast difference in Panama's ancient seas

An unconventional study utilizing microscopic shark skin denticles has uncovered a dramatic disparity in ancient shark populations between Panama's Pacific and Caribbean coasts. Researchers from the Smithsonian Tropical Research Institute analyzed these tiny, tooth-like structures shed from shark skin, which become embedded in reef sediments and can persist for millennia.

Their findings indicate that Panama's Pacific reefs, prior to intensive fishing, were home to approximately 20 times more sharks than their Caribbean counterparts. This stark difference existed even though the two coastlines are separated by only about 100 kilometers and share many of the same shark species.

The research suggests that oceanographic conditions played a crucial role. The Pacific coast of Panama benefits from seasonal upwelling, which brings nutrient-rich deep waters to the surface. This process fuels a more productive ecosystem, providing a greater food supply for large predators like sharks.

Conversely, the Caribbean coast of Panama features clearer waters that favor coral reefs but offer less sustenance for large shark populations. Despite the Pacific coast historically enduring much higher fishing pressure, over 98% of Panama's fishing occurs there, its shark populations appear to have remained more robust compared to the Caribbean, where denticle accumulation has decreased by roughly 75%.