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Images: One Man's Swamp Is a Fish's Nursery

Mangroves are like nursery schools for many of colorful fish that populate coral reefs. Among the roots and nutrient-rich waters in coastal mangrove swamps, juvenile fish get food and protection from predators until they mature and can migrate offshore to the reefs. These valuable nurseries are disappearing at an alarming rate, and so are the fish they support. (Illustration by E. Paul Oberlander, Woods Hole Oceanographic Institution)

Analyzing chemical clues in fish otoliths, or ear bones, MIT/WHOI graduate student Kelton McMahon seeks to identify which nurseries for juvenile coral reef fish should be protected. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

As a schoolmaster snapper grows, its ear bones, or otoliths, form sequential rings, much like a tree trunk, corresponding to different times in the fish’s life. Each ring in the otolith get imprinted with chemical isotopes from the waters where the fish had been living during that period of time—a fishy chemical address book.

With a scalpel and microscope, MIT/WHOI graduate student Kelton McMahon carefully removes delicate otoliths, or ear bones, each smaller than a grain of rice. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

Working at the Liquid Jungle Laboratory on the west coast of Panama, MIT/WHOI graduate student Kelton McMahon has been trying to reveal which mangrove swamp nurseries provide adult fish to which coral reefs. The answer will help coastal managers make decisions on the most important swamps to protect. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)