Dive Dry with Dr. Bill

#141: Zebra Goby

After several years of filming underwater, I finally released my first DVD entitled "Munching and Mating in the Macrocystis." Translated, this means behavior related to feeding and reproducing in the giant kelp forests of southern California. So far it has been very well received when I give video presentations to dive clubs throughout southern California. This educational video focuses not on identifying marine species and giving their scientific names, but on developing an equally important skill when underwater... observing the unusual behavior displayed by fish and invertebrates commonly encountered by divers. The major "take home" message is to slow down, open your eyes and really observe what is going on underwater.

The focus of this week's column is a fairly common fish that many divers never see in our dive park. In part this is because it is small (1-2"). Dr. Milton Love says the "world record" is 2.25" although it certainly wasn't caught with rod-and-wheel and weighed in at the official weigh station by Rosie's! Despite its beautiful blue and red-orange body, its coloration is subtle and seems to make it partially camouflaged ("a stealth fish") compared to its much more obvious relative the blue-banded goby. It is also present in much lower densities than its more obvious congener (member of the same scientific genus).

Zebra gobies are found as far north as Carmel Bay to Clarion Island, Mexico. They are most common south of Pt. Conception. These fish are usually found around irregularities in the rocky reef surface.

Until I researched this column (you think all this comes straight from my head?), I didn't realize that these fish are simultaneous hermaphrodites. Remember my recent column on strange sex lives? This means they have "both" gonads at the same time, with tissue that functions as an ovary and tissue that serves as a testis. Imagine the hormonal chaos this must cause in their tiny bodies. However, individuals may tend more strongly towards one "gender" or the other, with some functioning entirely as females (but none strictly as males). The blue-banded goby also exhibits this reproductive strategy.

Egg laying occurs during the warmer months (May-October). Dr. Love says that only about 150-800 eggs are produced, which is understandable given their small size. They are deposited in a wide range of hiding places such as rock crevices and empty shells. These nests are guarded until the eggs hatch. The larvae drift in the plankton for up to five months and settle on their new reef from late summer to mid-winter. In this case, the "acorns" may fall a long way from the tree, allowing the zebra goby to colonize new and remote areas (including Catalina as it was forming). The adults usually survive just one year, but some may live up to two years.

Adult zebra gobies feed on small invertebrates that live on the rocky reef surface. These include a range of copepods, isopods and amphipods. On at least one occasion I've documented them cleaning another fish. I was filming my favorite moray near the Jacques Cousteau memorial plaque in the Park. When I reviewed the footage that evening, I discovered that one of the zebra gobies that cohabit in the moray's hole (along with the cleaner shrimp and blue-banded gobies) darted off the rock surface and picked a small invertebrate off the moray's body.

These tiny fish are very camera shy when underwater paparazzi like myself (or potential predators) are around. Unlike their publicity seeking blue-banded relatives, they dart into hiding places whenever my lens comes close. Fortunately former island resident Erik Erikson gave me a few good images years ago to use in my videos and other educational efforts. He never did tell me his secret for capturing them.

As I've written before, common names for fish can be confusing. While searching the Internet, I discovered that there is a "zebra goby" living in China as well. I may just have to fly off to Hainan Island in southern China, a dive destination on my "dream" list, and check that one out as well. It may also be seen from the Red Sea to the Maldives to the Marquesas offering a few other dream dive destinations to visit along the way. Any foundations out there want to finance this trip? This confusion with common names is why biologists use a species' scientific name which is unique. In the case of our local zebra goby, that is Lythrypnus zebra while the Chinese zebra goby is Ptereleotris zebra, or is it Ptereleoris zebra or Pterapogon zebra or Pogonoculius zebra or Stanulus talboti? These were all scientific names for that fish that I found on the 'Net. No confusion there!

In my web browsing, I also discovered you can buy one of our zebra gobies on line for a mere $35 (not including shipping). Save your money and buy my DVD... it's cheaper and more environmentally appropriate! If I can get a few thousand folks to ante up, I can finance my research trip without applying for a grant... or, more likely, pay the mortgage!

© 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.

Zebra goby close up (images courtesy of Erik Erikson); lower right- a zebra goby
with a blue-banded goby for comparison.

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