If you see a rather odd-looking fish lying or swimming on its side in the Monterey Bay Habitats exhibit, you're watching one of the flatfishes. One of these species, the California halibut, can be identified by its large mouth and a lateral line that arches high over the side fin. Notice that both eyes are on one side and pointed upward. This side of the fish is brown or blackish with light and dark splotches—the side without eyes is usually white.
The eyes of the flatfish have an important feature—they're sensitive to patterns. The fish matches its skin coloration perfectly with whatever sandy or pebble bottom it rests on. You can watch this color change by visiting the flatfishes exhibit in the sandy seafloor habitat of our aquarium.
Even though adult halibut live in offshore waters, juveniles grow up in shallow-water bays and estuaries. Dredging and filling in bays and wetlands have destroyed many of these habitats. More marine reserves, including these wetland nurseries, would protect juvenile halibut and the adult spawning population.
Take care handling a California halibut. It has what is unusual for a flatfish—a large mouth with many sharp teeth. And it bites!
California halibut hide by burying themselves up to their eyes in the sandy seafloor. Although they seem to be a lazy fish, they're quite active. They swim in anchovy schools and even leap out of the water while chasing an anchovy (their favorite food).
A flatfish begins life as a normal-looking fish larva with an eye on each side of its head. But in about 13 days one eye starts roving, migrating around the head to take its place next to the other eye. When the change is complete, the halibut is still less than one inch (2.5 cm) long, but ready to live life sideways. Each species matures either with the right side up or with the left side up except the California halibut, which seem able to go either way.