Those of us who have spent many happy hours snorkeling in coral reefs tend to look at the big fish that we see in the reef. Groupers, sharks, rays, and parrotfish attract our attention. We can easily miss what makes the reef ecosystem work so that the larger fish can live there. Scientists are learning about cryptobenthic fish in the coral reefs.
Hanging around the reefs are tiny fish that are less than five centimeters long and easily escape our attention. They are known as cryptobenthic fish, and they exist in various species, some of which are known as blennies and gobies. Large numbers of them live in the rocks and crevices, and many of them are nocturnal.
Science News (June 22, 2019) reported on a recent study by scientists from Simon Fraser University in Canada. The study shows that these small fish provide a base to the food chain and allow the larger fish to survive. They don’t venture far from the corals that are attached to the floor of the reef. The cryptobenthic species include 17 families of fish that scientists have identified so far. Researchers in the past have overlooked most of them. Deron Burkepile, an ecologist at the University of California at Santa Barbara, says: “Their role is extremely important. We have definitely overlooked these little cryptobenthic species.”
One of the most studied fish in the ocean is a three-inch long shore fish called the frillfin goby (Bathygobius soporator). This little fish has even gotten attention from the New York Times which ran an article about studies by Dr. Jonathan Balcombe on this fish and how it survives (May 15, 2016).
This fish lives in the intertidal zones in the Atlantic Ocean. When the tide goes out, the fish lives in small tidal pools which are isolated and free of the large predatory fish which pose a threat when the tide is in. The problem is that these small pools can be hunting grounds for shorebirds and crabs so sometimes the fish needs to change pools. The goby does this by jumping out of its pool and landing in a nearby pool that offers better protection. The obvious problem with making this jump is knowing where the next pool is to land in it and not on bare rock. In 1971 a study was done at the American Museum of Natural History to see how the frillfin goby learns where to jump and how far to jump to land in the pool. Their conclusion was that the goby swims over the area at high tide and makes a mental map of the topography of the sea-floor. It can use this mental map 40 days later to escape from a predator. Essentially they have a mental GPS that allows them to make what would otherwise be a very dangerous escape.