Bands and layers of gray, brown and yellow sedimentary and volcanic rocks dominated the scenery above the water, while the submarine landscape was carpeted with several species of brown algae growing on the boulders which littered the bottom. Among the waving fronds of the algae, slipping between the boulders and in the waters all around were a great variety of beautiful fish like this Cortez angelfish and its cousin the king angelfish.
Those of us who had snorkeled in the waters of the Caribbean found these fish to be quite familiar, for good reason. Many populations of reef fish which previously occured in both the Pacific and the Caribbean basin were divided by the rise of the Isthmus of Panama about three million years ago. The span of time since this event has been enough for the populations on each side of the land bridge to evolve into new species which still bear a close resemblence to their relatives on the other side of the barrier.
The Cortez angelfish, in the genus Pomacanthus, has several congeners in the Caribbean including the French and gray angelfishes, while the king angelfish is in the genus Holacanthus, along with its Caribbean cousins the queen and blue angelfishes.
It was exciting to consider this example of evolution in action and even better simply to watch these beautiful fish going about their lives in the rich waters of the Gulf of California.
