Dive Dry with Dr. Bill

013: Flatfish

The Star Wars saga has conditioned us to accept strange-looking creatures, especially those that frequent some of the watering holes in those episodes. Well, in my "watering hole," the Casino Dive Park, there are some pretty strange looking creatures as well, only they didn't emerge from George Lucas' fertile imagination.

We are all familiar with fish like the garibaldi, kelp bass or opaleye that swim through the water and have eyes one on each side of their head so they can see in either direction. Such eye placement does not benefit flatfish like the halibut, sole, turbot, or sanddab as they rest "sideways" on the bottom. If their eyes were on each "side" of the body, one eye would be useless, staring down into the sediment!

To adapt to their non-comformist fish lifestyle, adult flatfish have both eyes on one side of the body which has become the upper or dorsal surface. The two flatfish featured today are the C-O sole (or turbot) which has both its eyes on the right side, and the California halibut which can have both eyes on either side (this one's are on the left side). ** The C-O sole is the flatfish I most commonly encounter in the Dive Park. It is often well camouflaged with patterns resembling the sandy bottom, but can also be quite colorful if it is found in rocky habitats where colorful algae may occur. These sole will also flip sand on their bodies to further camouflage themselves. This species reaches a maximum length of 14" and is found from Alaska to northern Baja in depths up to nearly 1,200 feet. It is most easily identified by the "C" and "O" markings on the tail.

Although common, very little is known about the C-O sole. They spawn during spring and summer, with the females releasing eggs that drift in the plankton and later settle after hatching. Food consists of animals that live in the bottom sediment like worms, as well as crustaceans and small fish.

The California halibut is a much larger flatfish, reaching lengths of five feet and weighing in excess of 70 pounds. Females may live 30 years or more. This species is found from Washington to southern Baja. They are much less common in the Dive Park than their smaller relative.

Adult halibut eat anchovies, grunion, other fish, squid and octopi. They are known to actively pursue schools of anchovy, even leaping out of the water in pursuit of them. The young fish eat small crustaceans living on the bottom. Halibut bones are found in Native American kitchen middens, and the species is an attractive target for recreational and commercial fishermen. However, catches have declined markedly since the 1920's.

Halibut may spawn throughout the year and peak reproduction may occur at different times in different years, depending on environmental conditions. The eggs and larvae are found drifting in the plankton, but usually relatively close to shore. The larval fish have their eyes on each side of the body, but as they settle one eye begins to migrate to the other side (the "light" rather than the "dark" side in Star Wars terms!). Based on studies of tagged halibut, Dr. Milton Love of UCSB believes that few young halibut settle in the Channel Islands region and the fish around the islands may have swum over from the mainland (and not at warp speed!).

© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Image caption: Fatfish in the Casino Dive Park: C-O sole partially buried in sand; C-O sole swimming away;
head of large California halibut; California halibut swimming away

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia