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Dive Dry with Dr. Bill

#686: Night and Day... You Are The "One"

Spring has sprung and the time is approaching for the good doctor to resume his night dives in the park. As the water warms and more folks decide to enter it, I elect to dive at night when the crowds have wandered off to the restaurants and bars or a movie in the Casino Theater.

I do very little night diving during winter and spring, but not because I'm some sort of warm water wussie. The water has actually been fairly warm thanks to El Niño. However, that's the time when the noxious devil weed (Sargassum horneri) covers our rocky reefs and makes it near impossible to find much of interest. The only positive is that I rarely have much video to edit after a nocturnal dip during those times of year.

I've written previously about the change in shifts that one observes underwater as the sun sets and the moon rises. Some fish hide in the reef or sleep, hoping to avoid the predators that often come out at night to crunch and munch. Often times they also change color to create better camouflage when sheltering.

A good local example of this is the female sheephead (Semicossyphus pulcher). During the day these lady wrasses are pinkish in color and often seen digging holes in the sand to search for clams, worms or other tasty (?) fare. At night, when they secrete themselves in between the boulders of Casino Mole, they turn many different colors from brick red to charcoal gray and are usually mottled to break up their outline.

Thanks to our recent late season drizzle, I was sitting in my bathrobe at my computer trying to finally identify all the fish I'd filmed in the Philippines three years ago. This is a somewhat daunting task due to the high biodiversity of the region. Not only are there billions and billions of fish, but there are also a gadzillion different species. Often only tiny characteristics distinguish them so you need both a good field guide and good eyes. Good luck on that, Dr. Bill.

There are also a few fish that stump me. I categorize them as unidentified and don't post pictures of them since that would make my ignorance all too obvious. However, one truly stumped me and I was determined to find out what it was. There wasn't a single picture of it in my field guides to the region but I was pretty certain it was a member of the fusilier family.

Now field guides are great, but they are often based solely on images the author has taken. Not every fish gets a perfect image taken for the books. So I turned to Facebook, which I joined way back in 2004 when it was still a relatively unknown website largely limited to my alma mater. And yes, a lovely and highly intelligent Harvard lady had something to do with creating my initial profile.

I went to the marine creature identification page and posted the best image I had of this unknown species. Very quickly I had the ID from several members there. It was a bluestreak or dark-banded fusilier (Pterocaesio tile), but it looked nothing like the ones I've filmed in the Philippines and Palau. Then I realized all the images that looked similar had been taken at night.

Yep, this fish adopts several color phases. During the day it may be mostly blue with a dark line across its side... or reddish with a large neon blue blotch on the side. I knew these color variants from my daytime filming. However, its nighttime coloration was markedly different as you can see in the associated images. I learned it also may adopt this coloration when being cleaned by fish such as wrasses.

Being a marine biologist ain't always easy (but t is almost always fun). The same species may exhibit a totally different look as a juvenile, female or male. The California sheephead is an excellent local example of this. Add to this the fact that the same species sheltering at night may adopt a completely different color pattern. Heck, I may have to learn five or six different color schemes to identify a single species! Yeah, I know... life is tough.

© 2016 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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Daytime color patterns of the bluestreak or dark-banded fusilier; nighttime coloration and charcoal
rendering of female sheephead sheltering at night in the dive park.

This document maintained by Dr. Bill Bushing.
Material and images © 2016 Star Thrower Educational Multimedia