One Big Butterflyfish!

by B. N. Sullivan

Lined Butterflyfish (Chaetodon lineolatus)

This is the Lined Butterflyfish (Chaetodon lineolatus), perhaps the largest butterflyfish species in the world.  Adults measure about 30 cm (12 in) in length -- nearly twice the size of the majority of butterflyfish species.  The Saddle Butterflyfish (C. ephippium) is the only other butterflyfish species that approaches (and may sometimes match) the size of C. lineolatus.

This is an Indo-Pacific species widely distributed throughout the region.  We have seen them in the Red Sea and in Hawaii, but they are known to occur as well along the shores of East Africa, Southern Japan, and Australia's Great Barrier Reef.

We have observed them almost always in pairs.  They hang out around coral reefs, which is not surprising since they feed primarily on coral polyps.  It is not unusual to see a pair of these fishies bobbing along side by side as they peck away at a coral head.  According to the World Register of Marine Species (WoRMS) page on C. lineolatus, they also feed on anemones, small invertebrates, and algae.

Lined Butterflyfish are believed to be a long-lived species.  Although no one knows for sure how long their natural lifespan is, it is likely several decades.  In places like Hawaii where local divers may visit the same site again and again over years or even decades, the divers learn to recognize individual animals that live there.  We got to know a certain pair of C. lineolatus living in Honaunau Bay, on the South Kona coast of Hawaii Island and have seen them there again and again over a period of at least 15 years.

Honaunau Bay is a popular snorkeling and shore-diving  spot for tourists as well as locals, and many have fed the reef fish there over the years.  While guides and tour operators currently do a good job of discouraging this practice, the fish seem to have long memories.  The pair of Lined Butterflyfish in the image below still approach divers, ever hopeful for a hand-out.

A diver interacts with some Lined Butterflyfish in Honaunau Bay, Hawaii

Animal, Vegetable, or Mineral?

by B. N. Sullivan

Take a look at the photos below. What's your guess: animal, vegetable or mineral?

At first glance they look like some kind of vegetable, don't they? Perhaps cauliflower or broccoli come to mind?

In fact, the correct answer is "animal."  The images above are macro photos of a type of soft coral in the genus Dendronephthya.  The common name for this variety is "Broccoli Coral," and you can see why that is so.

Although this kind of coral can resemble broccoli in appearance, it definitely is not a plant.  It is a colony of animals -- the coral polyps. The polyps arrange themselves in bundles at the ends of the rubbery stalks. Each polyp has exactly eight short, feathery tentacles. In order to feed, the polyps open and close their little tentacles, grabbing tiny nutrient particles that are suspended in the water.

This feeding activity happens mostly at night.  During daylight hours, the polyps retract into tiny bundles, as you see in these photos.

The final photo, below, shows what the entire colony looks like.  All of these photos were taken in the Red Sea, but this species also can be found elsewhere in the Indo-Pacific region.

Underwater Photography: Why you need artificial light

by B. N. Sullivan

We see it happen all the time:  Tourists go snorkeling -- sometimes for the first time in their lives -- and they are excited by what they see.  They decide they want to take pictures of all the pretty fishies and corals to show their friends back home.  They buy a waterproof camera, they snap away, and they are sorely disappointed when they see the result.  Most of the photos are blurry, and though they thought they were shooting in color, all of the images are monochrome -- blue monochrome.

For quite a few reasons, taking photos underwater is very different than taking photos on land.  For one thing, you have to shoot through water, which is a much denser medium than air.  The farther away you are from the subject, the less likely it is that you will get a clear, crisp image regardless of which lens you select.

The main difference, though, has to do with light.  As sunlight penetrates water, it is gradually absorbed.  That is why the deeper you go, the darker it gets.  The longer wavelengths -- the reds and yellows -- are absorbed faster than the shorter wavelengths, i.e., the blues and greens.  Things look bluer the deeper you dive, because the longer wavelengths are effectively gone.

So, while shooting photos underwater in natural light can produce some nice images,  even at very shallow depths in very clear water the result always will be quite monochromatic.  You can't fight the laws of physics!

In order to capture colors and details underwater, it is necessary to be as close as possible to the subject and to use strobes (flash) to light it.  Here are some examples of sea turtle photos that will illustrate the above points.

Green Sea Turtle -- natural light at about 8 meters depth

This first image is a typical natural light photo at relatively shallow depth -- the blue monochrome effect.  It happened by mistake when my camera strobes failed to fire as I pressed the shutter release.  Pictured is a rather elderly Green Sea Turtle (Chelonia mydas) with a Remora (Remora sp.) -- AKA "shark-sucker"-- attached to its carapace.  The photo was taken at Pulau Sipadan, Malaysia.

Green Sea Turtle -- natural light at about 2 meters depth

The second image also was shot in natural light, but just below the surface and at very close range.  This Green Sea Turtle passed right beside me just as I began my descent from the surface, and I had no time to do anything but aim and shoot.  Since the turtle was so close to me and we were barely two meters deep, the details were captured reasonably well  (including that gunk on the carapace).  Notice, though, that the background is quite blurry and blue.  This image was shot in Hawaii.

Green Sea Turtle -- lit with a single strobe

In the final example, another Green Sea Turtle at Pulau Sipadan  was lit with a single strobe from the right side of the frame.  The colors in the carapace and the markings on the turtle are well captured, and the soft and hard corals in the foreground are well defined.  The fishes in the more distant background are fuzzy, which is typical for this kind of shot.

Note: An earlier version of this article was published in 2009 in Photosynthesis on ScienceBlogs.com.

Humpback Whale Tail at Dusk

by B. N. Sullivan

Last evening at dusk, we went sailing with some family members on Kawaihae Bay, on the Kohala Coast of Hawaii's Big Island.  The winds were light, the ocean surface was calm, and the mood was peaceful.

We were escorted for awhile by several Humpback Whales.  The whales seemed to be in a placid mood as well.  We saw no breaches or other dramatic behaviors.  Instead, the huge cetaceans glided along near the boat, occasionally diving below the surface for a time and then reappearing to blow and breathe.  I snapped this photo of  one whale's tail just as as it began a dive.