Dive Dry with Dr. Bill

114: Guadalupe Cardinalfish

Rarity has a certain appeal for most people, including biologists. We collect things that are rare... coins, postage stamps, Catalina pottery and baseball programs from Chicago Cubs playoff appearances. Because they are rare, they often have economic value. For biologists, rare species often mean the possibility of a scientific paper or even a chance to give their name to a new species.

As a collector, I appreciate the value of rarity as an investment. However, as a biologist I adhere to the beliefs of my icon Ed "Doc" Ricketts of Steinbeck's Cannery Row fame. Ed felt that it was not the rare species that had the most "value," but the more common species in an ecosystem. It was these abundant elements that had the greatest ecological impact in the "mutual eating society" and therefore were very worthy of further study. How many biologists value the kelp bass or the jack mackerel (except as food)?

In this column I am going to diverge from this position and deal with a species that is indeed rare in our dive park. I'm referring to the Guadalupe cardinalfish which I've only encountered twice in my years of diving. This species is uncommon in southern California waters and most field identification books don't even mention it. I've had to turn to books about fishes in Mexican waters since they are more common there. Its reported distribution is from Farnsworth Bank off Catalina or San Clemente Island south to Cabo San Lucas.

The Guadalupe cardinalfish is small, reaching about 5" in length. It is also secretive, hiding in rocky crevices and holes during the day and venturing out primarily at night. Like many other nocturnal fishes, it is red in color. There are no obvious markings such as bars, spots or stripes as are found in several other cardinalfish. Red is a color that gives it night-time "camouflage." Since there is almost no red light under water (especially at night!) these fish appear black in the dark waters. Some cardinalfish stay in tight schools and do not venture far from shelter when there is a full moon. No, this is not due to vampire fish or bat rays. The increased light levels make them easier for predators to spot.

The pair of cardinalfish I observed in the dive park were within the protection of a small hole in the rocks of the Casino breakwater. I might not have detected them had it not been for my video light which highlighted their bright red color. Their location made it difficult to film them, but I did get a brief sequence that was acceptable (see image).

I often see several related species of cardinalfish when I dive the waters of the Gulf of California (Sea of Cortez). They are really a subtropical and tropical group frequently found on reefs in warmer waters. Worldwide there are over 200 different species. Like "ours," the other species in Mexican waters are reddish in color but have spots, bars or both depending on the species. In those waters they are much more common and are often present in large groups in caves or other protected areas. These species feed on plankton, small crustaceans and fish.

Most cardinalfish are mouth brooders. Rather than building a nest like our garibaldi, or casting their eggs into open water to drift in the plankton, they incubate the eggs in their mouths. This makes it rather difficult to grab a quick snack, so I assume they do not feed while brooding (help, I swallowed the babies). The ones I observed were not reproducing since their mouths were empty. Because they are members of a warm water group, it is possible that our temperatures are a bit too chilly for reproduction. Of course it is also possible they just weren't in the mood.

© 2004 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.

Guadalupe cardinalfish sheltering in a protected area within the Casino breakwater.

This document maintained by Dr. Bill Bushing.
Material © 2004 Star Thrower Educational Multimedia