Diving the Kona Coast: Bird Wrasse

Another example of how vastly different the sexes can appear in the same species of reef fish in Hawai'i. The plain little fish above are initial phase Bird Wrasse which can be either male or female. They are small (~3 in.) and, except for a little streak of red on their snouts, fairly drab. Below is the supermale of the species which is substantially bigger (6 to 7 in.) and endowed with vivid blue and green colors including a patch of nearly-neon green above the pectoral fin.

All Bird Wrasse have curved snouts that allow them to pull their prey from among the arms of branching coral. This feature resembles the beak of an endemic bird, the Scarlet Hawaiian Honeycreeper or i'iwi. These fishes swim swiftly and erratically making them very difficult to photograph.

Wrasse sexuality can be a somewhat complicated matter. For purposes of today's post I'll just point out that Bird Wrasse supermales begin life as females and then, for reasons unknown, some morph into the colorful and socially dominant form. Gender-changing is common in wrasse as well as parrotfish.

By no means was this a "Chamber of Commerce" type of day in Kona. When I got up there was a little bit of sun and blue sky over the mountains but very gray and cloudy over the ocean. During the first dive I had a little sunlight but it got progressively darker as time went by. The scene above was taken between dives. As I geared up for my second dive it began to drizzle very lightly. But I was already wet and planning on getting wetter so I went ahead. The second dive was good, but topside it was raining buckets. To the south there was thunder and lightning and north in Kailua-Kona funnel clouds were spotted over the ocean. Pretty wild!

The weather made underwater visibility a bit like night diving. I saw this juvenile Blackside Hawkfish early in the dive. These fish undergo a dramatic change in coloration as they mature. Later in the dive I found an adult specimen. You can see from the photo below how this fish changes as it grows.

A variety of Wrasses were on the reef on the first dive. The beautifully colored fish above is a Yellowtail Coris. All wrasses swim by beating their pectoral fins, holding the tail stiff and using it only for steering. They flit around somewhat erratically and are difficult to photograph.

Above are three female Bird Wrasse darting about the reef. They have a characteristic curved beak that resembles the beak of a Hawaiian bird called a Honeycreeper. The males are similarly shaped but are bigger and colored dark green and blue.

The Saddle Wrasse is one of the more common fish on Hawaiian reefs and is easily identified by its orange "saddle" just behind the head. It has beautiful magenta markings at the base of the anal, dorsal and caudal fins.

Near the end of the first dive I came upon a cloud of stirred up sand. At first I thought it might have been the result of a couple of Square Spot Goatfish feeding in the area. But then I saw a Spotted Eagle Ray glide through the area. These graceful swimmers are becoming more commonly seen around Honaunau.

After an hour's surface interval, I returned for a second dive. This Manybar Goatfish is displaying the chin barbels that give it the family name as they somewhat resemble a goat's beard. This individual tipped me off to the presence of a Day Octopus as the two creatures sometimes hunt cooperatively.

Here are the two hunting partners together.

This particular octopus was a little shy so I only took a couple photos of it, then moved on.

Death is an integral part of nature's plan on the reef as elsewhere. This Pelagic Jellyfish has drifted to its demise in the bay. It's once flowing tentacles have been eaten down to nubs and a big gash runs across it's bell. It was being nibbled on by a Ringtail Wrasse, which fled as I approached. It's bell pulsated weakly and ineffectively, unable to lift it off the sea floor.

My diving day ended with an uncommon sight. A medium-sized Great Barracuda hovered near the surface in shallow water. When we lived in the Florida Keys we saw 'cudas all the time and they were quite bold. Often they would follow you for most of the dive. Here in Hawai'i you don't see them very often and they tend to be shy around divers. The ones I see here are generally a lot smaller than their Western Atlantic and Carribean kin.

No more dives are planned until after Christmas but hopefully I'll get one more day of diving in before the end of the year.

Diving the Kona Coast

Wednesday, January 20, 2010

Sexual Dimorphism Redux

Monday, December 21, 2009

Dive Report for Sunday 12/20/2009

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