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Dive Dry with Dr. Bill

#492: A Fish That's Almost Patriotic

With the big Fourth of July holiday coming up, I thought I'd take some time to write about a fish that wears its true colors every day of the year. I'm referring to the blue-banded or Catalina goby (Lythrypnus dalli). Well, all but the white. It's body is a beautiful reddish to orange in color with two to nine blue stripes that look almost like a neon sign. Dr. Milton Love refers to the red as "crimson," the color of my alma mater Harvard, and one name for its football team! Despite their species name, they are not related to Salvador Dali (note the different spelling) although they look like a painting, and even Dr. Milton Love doesn't know what the heck the genus name Lythrypnus refers to.

These fish are so colorful that if they were larger than their maximum length of three inches, folks diving at Casino Point Dive Park might think they were in the tropics. And for some strange reason, my dive computer recorded a minimum temperature on my last dive of 86 degrees (but only 62 F the previous dive). I think it may be telling me something. As it is, despite their diminutive size the color makes them quite noticeable... even more so in those years we experience a population explosion and their tiny babies dot most nooks and crannies in the reef!

These gobies are known from Morro Bay south to Peru, and are common south of Pt. Conception. They range in depth from a few millimeters to 250 ft, thus breaking my personal best by 50 so I can't confirm that end of their range. Dr. Love states they can survive temperatures up to 88 F, but struggle to breathe when the thermometer rises above about 73 degrees.

Blue-banded gobies are conspicuous because they often sit out on the reef during daylight and watch for passing prey. Given their size, this consists of small plankton and organic matter rather than anything "Super Sized." They can be seen darting up off their perch and grabbing a bite to eat, then settling back down to wait for the next course. Milton states that most feeding occurs at dawn or dusk, but I rarely dive those hours and frequently see them feeding all day if potential food appears. Munchies include copepods, amphipods, larvae and even worms, small snails and other molluscs. In turn they are eaten by black-and-yellow rockfish (which I've been seeing recently in the park), kelp bass and other predators. On my night dives I don't see them as often since they retreat into crevices.

Reading Dr. Love's incredible Certainly More Than You Want to Know About the Fishes of the Pacific Coast enlightened me on their social and sexual behavior. These fish congregate in small groups with a dominant male lording over a harem of babes. Heck, I can't even find one women! If the male disappears, the largest female will change sex and take his place. Sometimes two fish will face off with their fins erect and their mouths wide open in an apparent dominance display. That is not the same as a dominatrix display (at least from what I'm told). Spawning takes place mainly from February to September in southern California, but can occur any time of the year a goby gets the notion.

Blue banded gobies are sexually mature at about one month (how incredibly precocious). The male initiates courtship with a female by sending quivers down the side of his body, then darting towards her and placing a gentle "love bite" on her tail and swimming into the nest. If that doesn't entice the lovely lady, he repeats the process... over and over again. Perhaps I should try that myself. If successful, the lady may remain in the nest for an hour or two and deposit her eggs. An individual female may lay between about 60 and over 2,000 eggs. According to research by Behrents in the 1980s, only one girl enters the nest at a time... but there may be eggs from several females in the same nest.

Actually their sex lives are much more complex than one would suspect. Unlike fish such as the sheephead, these gobies do not start off as one gender and transition to the other. They can switch sex back and forth... and even have both male and female reproductive parts at the same time. That would make Saturday nights at the Marlin Club VERY confusing (even more so than they already are)! Some males dominate and score all the ladies and territory, while others sneak around and fertilize eggs behind the backs of the dominant males.

The young disperse in the plankton as larvae for 2-3 months and settle onto the reef between June and January when they are about half an inch in length. Both young and adult often seek shelter near sea urchins, especially the black or Coronado urchin with its long, sharp spines. I don't envy this fish's lifespan as the geezers may only reach a ripe "old" age of 20 months. I'm glad I've lived long enough to collect on my investment in Medicare and Social Security! Happy Fourth of July to all.

© 2012 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Close-up of blue-banded goby and goby on the reef; goby jumping up to grab food and male with a "harem" of two.

This document maintained by Dr. Bill Bushing.
Material and images © 2012 Star Thrower Educational Multimedia