Dive Dry with Dr. Bill

#146: Blue Banded Goby
Not Quite Red, White and Blue

The blue banded goby is one of the most common fish observed by those divers and snorkelers who open their eyes and do not rush past our reefs. Although these fish are small (up to 2 1/2 inches), their bright coloration gives them away to all but the most color blind of divers. Their bodies are a red or reddish orange with several blue bands running vertically along their sides. If they had a patch of white, they might be a perfect fish for this Independence Day holiday weekend. Since they are often found in relatively shallow water, their red coloration may still be detected despite the fact that color is filtered out of the water column first.

Although often called the Catalina goby, they may be found from Morro Bay to central Baja and in the Gulf of California (Sea of Cortez). They are especially abundant in southern California. Although they are occasionally found at depths down to 250 feet, they are most common above 60 feet. Another "blue banded goby" is found in the Galapagos, and does look somewhat like our own. These gobies are quite territorial and are usually seen resting horizontally or vertically on the reef surface. They will defend their territory but usually have a protective crevice nearby to duck into if necessary.

Although small, these gobies are meat eaters... that is if you consider zooplankton, bryozoa and sponges to be meaty fare! I prefer a nice flank steak, especially barbequed over Fourth of July weekend. Their main predator appears to be the kelp or calico bass. I often see these tiny fish hiding under the protection of a sea urchin's sharp spines. They seem to look out taunting me to try to capture them. Of course the only way I "capture" fish these days is on videotape. Besides, have you ever seen a "filet of goby" at Armstrong's?

Blue banded gobies are another fish that exhibits a strange (well, to us... their opinion may differ) sex life. They can be simultaneous hermaphrodites, having both male and female organs at the same time. Some may be "mainly" male or "mainly" female. Or they can be sequential hermaphrodites, switching gender from female to male. The more "conservative" or "conventional" ones can be all male or all female. It is said that males have longer dorsal fins than females, but with all these possible combinations of gender I wouldn't rely on that "metric." Imagine how confusing this must be when it comes time for courtship! Mating may occur over a wide time frame, from February through September with a peak beginning in May and lasting through the summer.

Due to their small size, females produce as few as 60 but as many as 2,200 eggs which are usually laid in a protected crevice or empty shell. Like many other fish species, the male guards the eggs until they hatch. Why would nature put the "man" in charge of babysitting? Perhaps it is because they are more aggressive and make better defenders. They are far less skittish than their local relative, the zebra goby. Or possibly because (sorry guys) they are more expendable than the female. If a predator gulps them down, the egg producers still survive and simply find a new mate. The eggs hatch and the larvae drift with the plankton for at least two months before settling back onto reefs at about half an inch in size. These small fish rarely live more than 18 months, making them very short-lived for fishes.

Fish expert Dr. Milton Love states that blue-banded goby populations may undergo tremendous changes in density over time. This is often referred to as a "boom and bust" cycle. Last year our rocky reefs were literally covered with red and blue hues. I saw blue banded gobies, "young" and "old" (relative terms given their longevity... or "shortivity" if you prefer), all over the reefs in the dive park. It was almost like a fireworks display as these numerous colorful fish flitted about on the rocks.

Blue banded gobies are a fairly popular salt water aquarium fish. Because they are temperate rather than tropical, they require temperatures lower than most salt water aquarium species. Because of their popularity, they were subject to large-scale "harvesting" off Catalina and elsewhere by collectors using suction devices. The Catalina Conservancy Divers (CCD) spearheaded an effort to stop this collecting until its ecological impact could be determined by scientific studies. One could view these beautiful little fish as our equivalent of the clown fish in "Finding Nemo..." potentially "loved to death" (or at least to local extinction).

© 2005 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.

Blue banded goby (photo credit: Xiaoyan Li).

This document maintained by Dr. Bill Bushing.
Material and images © 2005 Star Thrower Educational Multimedia