Seventeen families of fish count as cryptobenthics, but aside from seahorses (and perhaps gobies), most are obscure. Blennies, dottybacks, clingfishes, and dragonets—they’d be household names if only they were a little bigger, Brandl thinks. “I suspect that if we were to blow them up to 20 times their size, we’d consider some of them to be the most beautiful fish on the reef,” he says.

The small size of these fish also limits how many eggs they can produce, “which means they have to be extremely religious about making sure those actually hatch,” Brandl says. Some incubate their eggs in their mouths, forgoing meals until the larvae break out. Seahorse males lug around their eggs in breeding pouches. Sandgazers carry around a ball of eggs under their pectoral fins—a behavior called “armpit breeding.” These tactics mean that cryptobenthics are far better than other fish at converting eggs into larvae. When researchers count the baby fish in the waters near a reef, about 70 percent will be cryptobenthics.

For most of these larvae, life will be brief—even if they escape the jaws of predators. The pygmy goby, for example, crams its entire existence into just two months—the shortest life span of any backboned animal. Much of that time is spent as a larva, which quickly quintuples in size into an inch-long adult that lasts for just a few weeks. Living fast and dying young: That’s the cryptobenthic way. “They’ve broken with the fundamental rule of being a vertebrate, which is that you spend most of your time as an adult,” says Brandl. “They’re almost getting into mayfly territory.”

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All of this explains why standard surveys fail to capture how important these fish are. Ecologists typically study reef animals by measuring their “standing biomass”—that is, they grab all the adults in an area and weigh them. By this measure, cryptobenthics seem unimportant: Though there are plenty of them, they barely shift the scales, even together. But that metric is profoundly misleading, because it ignores just how many cryptobenthics are eaten, and how often they’re eaten.

By simulating the lives of these fishes, Brandl found that their generations tick by so quickly, and they’re so frequently preyed upon, that every individual is replaced seven times a year. That’s a huge mass of fish that we rarely ever notice, because it’s eaten almost as quickly as it is generated. Weigh the survivors at any one moment, and you’ll be unimpressed. But estimate the total mass of the dead, as Brandl and his team did, and you’ll find that cryptobenthics account for 60 percent of the fish flesh that is eaten on a reef. Abundant, calorific, and rapidly produced, “they’re the fast food of coral reefs,” says Gabby Ahmadia, who has studied cryptobenthics and is now a director of marine-conservation science at the WWF.