Dive Dry with Dr. Bill

#660: Making Babies!

Last week I wrote about the beautiful butterflyfish I filmed in the Egyptian Red Sea. In that column, I mentioned the scythe butterflyfish which apparently arrived in our waters from Mexico during a much earlier El Niño. About a decade ago I filmed youngsters of this species, suggesting these butterflyfish found our waters warm enough for the ultimate reason for existence of any species. Yep, you guessed it... to reproduce and continue its kind.

Over my nearly 50 years diving in the waters off Catalina, I have experienced a number of warm water events and seen a few immigrants taking advantage of the situation by arriving here either as larvae dispersing in the currents, or even as migrating adults. Frequently these warm-water critters find our winters too harsh and forbidding to survive. Those that do make it, often are unable to reproduce since mating generally requires a narrower range of temperatures than just surviving. Of course for any species to become established here in SoCal, successful reproduction is mandatory.

Three years ago I reported on a find by Ken Kurtis of Reefseekers in our dive park that I identified as a baby whitetail gregory or damsel (Stegastes leucorus). The little youngster resembled babies of its relative the garibaldi, but with a quite different color pattern. It disappeared after a series of storms and we thought it was lost forever. Then, a few months ago, I discovered an adult or subadult of that same species in the park. I thought it could be the same individual, an opinion that was shared by fish experts I consulted. So it appeared that the baby whitetail had survived a few winters and grown up. Of course I dubbed it the "lonely damsel" and assumed it would not reproduce on its own!

Then this summer I began hearing reports of more sightings of whitetails over in Lover's Cove. Angela from ScubaLuv saw one there, and Renzo Sampson encountered two while he was snorkeling. Hmmm... based on statistics, I doubted all these fish were of the same gender so perhaps it was possible they had reproduced in our waters. Just last week I heard from Becky Morrow at Howlands' Landing who sent me an image of a baby fish that they had seen up on the West End of the island. I quickly identified it as a baby whitetail. The question is, was this youngster a result of mating by the fish in our waters... or was its appearance the result of another larval stage swept up here by the currents.

Another species I've been following the past few years is the beautiful Guadalupe cardinalfish (Apogon guadalupensis). Catalina is at the northernmost extent of its geographic range, and I first filmed one back in 2004 at the dive park. Cardinalfish are mouth brooders, and the males hold the eggs in their mouths until they hatched. The one I saw 11 years ago appeared to have puffy "cheeks" suggesting it was "carrying" (without a concealed carry permit?), but I never saw any youngsters.

Several local divers including Chris Howard and Ruth Harris have observed male Guadalupe cardinalfish the past year mouth brooding eggs. I've filmed a few of them. Early this month I was lucky enough to record a male expel his eggs and then suck them back into the mouth. They do this either to oxygenate the eggs or to reposition them in the mouth. I also dive at night to catch them out of their shelters feeding after the sun goes down. Their red-orange color makes them less visible in the water to predators... until my video lights catch them. I make sure to swing my lights out of the way if a hungry kelp bass heads in their direction.

But did the eggs hatch into youngsters? That is the same question I had to ask about the whitetail gregory, the scythe butterflyfish, the finescale triggerfish and others which have entered our local waters. YES! They did. For several weeks now I've filmed a cluster of about two dozen little "kids." Like the adults, they hide in sheltered areas of the Casino Point breakwater during the day. I've marked the best group so I can relocate the site at night when landmarks (seamarks?) are not as readily visible. Each time I have returned at night, the youngsters are gone.

On a dive last night, I confirmed they are doing the thing that is critical to the survival of all individuals... out in the open munching! I was worried the other day when I spotted about six of the youngsters in their hole with a moray eel. The moray had been there all along, but I had to wonder if perhaps the youngsters had grown large enough to at least become hors d'oeuvres for the eel. I hope not!

I have little doubt that these babies are the result of local fish mating. If they had arrived individually as larvae, they could have "found" one another since many species can sense the presence of other members through chemical communication. However, I have a good feeling that the reproduction was local, and therefore completed the process of successful establishment. First, finding food to eat in the new environment to ensure the individuals could grow to maturity; and then reproducing to ensure the population can remain in the new habitat.

© 2015 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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Adult Guadalupe cardinalfish and male aerating eggs from mouth; cardinalfish babies and one with the moray.

This document maintained by Dr. Bill Bushing.
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