Fish EarRings

Under a microscope, the otolith, or ear stone, of a larval fish—a river herring—shows concentric rings. Every day the fish adds a layer of calcium carbonate to their otoliths, tiny structures in their heads used for balance and hearing. WHOI biologist and larval fish ecologist Joel Llopiz determines how fast the larvae are growing by measuring their otolith rings. Llopiz is studying factors affecting the growth of river herring, whose populations have declined dramatically, with funding from Woods Hole Sea Grant. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)