Microscopic Monsters of the Ocean: Grouper

Most anglers never get to see what this tasty bottom fish looks like as a larva.

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Grouper get big, really big. But have you ever wondered what they look like when they’re the size of a cherry tomato?

The life history of most game fishes is pretty amazing. Although some species may grow to more than 1,000 pounds, all begin life as one of millions of eggs the size of a small grain of sand floating about an ocean full of tiny predators, following a full-moon spawning session. Of those millions, thousands may be fertilized, but of those thousands fewer than 100 will survive past the larval stage.

They feed on tiny plankton, but are also fed upon by slightly larger planktonic predators. It is indeed a jungle out there in the open ocean. Growth, for the few that live, is rapid. Most larval forms of game and food fishes bear little or no resemblance initially to adults, often very different in shape and color, recognizable only to experts. They may resemble elaborate insects as much as fish. As they grow into small juveniles, often characterized by oversized eyes, the babies begin to gradually take on more of the characteristics of larger, older fish.

Few anglers ever get the chance for a close-up and personal look at game fish not much longer than a cherry tomato, so in this ongoing gallery of “microscopic monsters,” we’ll offer a rare look at a mini version of species most of us see as only adult fish.

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Most larval forms of gamefish bear little resemblance to adults. Would you have guessed this is a grouper? Ryo-Minemizu.com

You wouldn’t likely recognize this little fellow at first glance as a grouper. Still, its larval form isn’t so dissimilar from the adult, at least, not in comparison with a larval billfish, for example, which looks like some entirely different species from the adult.

Determining which species of grouper, given the hundreds of possibilities found all over the world, is a much more unlikely task. But grouper it is. You might refer to him as a “little guy,” but only for now. By the time this fish reaches seven pounds or so (should it survive that long), depending upon its species, it will be female, whatever its sex when small. After that, it may or may not be protogynous, changing sex again to become male.

This larva was photographed in the open ocean. Like many reef fish, grouper gather en masse at a certain time of year to spawn offshore. Their larvae remain pelagic for a month or two before drifting into inshore areas where they’ll associate with the bottom and, with any luck, grow to adult size.

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