Our Coralgoby Year

Redhead Goby Paragobiodon echinocephalus photgraphed by Ned DeLoach
Redhead Coralgoby, Paragobiodon echinocephalus

Eye-to-Eye with Cute

If it hadn’t been for a bit of movement, we would have never seen the pair of coralgobies living inside a fortress of branches fashioning a soccer ball-sized mound of cauliflower coral—one of hundreds of similar colonies fringing the knee-deep, inshore shallows of Ambon Bay in Indonesia. With our facemasks only inches away, two of the cutest fish in the sea scampered about their symbiotic home like mice in a maze. After several seconds of diver-induced panic the pair of Redheaded Coralgoby, Paragobiodon echinocephalus, settle down side-by-side in the shadows and peer up with big, beautiful, beseeching eyes imploring us to just go away. The inch-long fish, with fuzzy red heads, bright green eyes and roly-poly bodies shot Cupid’s arrows straight into our hearts. Not wanting to bother them further, we obliged, slowly finger walking our half-submerged bodies hippo-style along the outer fringes of the reef searching for gobies as we go. 

To our delight, we found ourselves in an unfamiliar fantasyland of seldom-seen fishes, including four additional members of the forever-cute coralgoby clan comprising two genera: Gobiodon and the shaggy-headed Paragobiodon. The discovery of so many new species would be a boon for expanding the photo galleries in our Tropical Pacific ID book. But, at that moment business was far from our minds. All we were thinking about while wading back to our skiff was how to get a photograph of the amazing pair of redheads—an intriguing image to top off our month-long jaunt across eastern Indonesia. 

Our major concern was a tight flight schedule home, which left us only a single day to get our shot. Fortunately, we still had our private boat booked. While slinging tanks into the boat, Semuel Bukasiang our guide for the week, and a veteran of distinction, estimated that high tide, optimal for shallow inshore diving, would reach its peak in the early afternoon. As our skiff skimmed back to the resort over water as smooth as a proverbial millpond everything was set, or so it seemed. At that moment, with images of gobies still dancing in our heads, neither of us had an inkling of the storm rumbling its way up from the Indian Ocean, or of the bruises and life lessons that awaited. 

The following morning we awoke to a freshening gale. By the time we descended the steps of our bungalow at 7 AM a brisk sea breeze had been sending spray over the seawall for an hour. Word of worsening conditions arrived with coffee. Minutes later Semuel joined us with an even more unsettling forecast along with a pressing decision. It seemed our only chance to visit the gobies would be in the coming hour, and even then conditions, especially carrying a camera in the surge, would make for some tricky diving. Driven by greenhorn grit, Anna and I, without hesitation, agreed to go for it. 

As expected, the shallows were in a rage when we arrived. Making matters worse the tide, only beginning to rise, exposed a patchwork of coral tops in the troughs between waves. The three of us, not quite sure what we were getting into, backrolled into the uproar, struggled to our feet, and staggered unsteadily toward shore. Anna was first to go down. Semuel and I quickly followed, upended by a wave that carried us across the bottom like leaves in a gale. Once near the edge of the reef and semi-stable on our hands and knees, the three of us set about searching for gobies as best we could. 

Within minutes, Anna spotted a pair of Redheads. Purging the last drop of air from my BC, I settled on the sand inches away from her pointing hand, dug my elbows into the bottom, and began searching for the tiny targets through the sand and debris. Even with a full tank and the eighteen pounds of weights scavenged from the dive shop floor, holding steady long enough to take a photo was proving next to impossible. 

Just as I caught a glimpse of Anna’s gobies an explosion of surge catapulted me onto my back. Righting myself, I crept back into position and hunkered down with renewed determination. Eventually the skittish pair settled down cheek-to-cheek just like the day before. But, try as I might, I couldn’t get a clear shot through the branches. Adding to my troubles, the surge was picking up, the sky was darkening and rain began peppering the back of my head like buckshot. Frustrated, fatigued and getting nowhere fast, I began circling the coral occasionally catching sight of a goby tucked deep in the tangle. Finally, sprawled flat and craning my neck, a small passage leading to what happened to be one of the gobies’ favorite perches appeared. But when I lifted the camera, the pair, with no intention of having their portrait taken, bolted to the other side of the coral head. The small opening leading to the perch seemed to be my only hope. There was nothing to do but wait.

Noting my predicament, Semuel settled on the sand across from me, and with a wave of his fingers sent the gobies scrambling in my direction. After several tentative passes they eventually perched right where I wanted them and stared into my lens with the soulful eyes of puppies in a pound. But before I could focus, the surge lifted my legs off the bottom and wrenched the viewfinder from my eye. By the time I regained composure the gobies were gone. This back-and-forth battle of wills between man and goby, that only lasted minutes, seemed to stretch into hours. All would have been lost had it not been for Anna — the best buddy a diver ever had. She came to the rescue, draping her tank-heavy body across my wayward legs—just the trick to save the day.

2012 – The Coralgoby Hunt Begins

Our blundering, but none-the-less consequential encounter with the Redheads set into motion a yearlong quest to photograph every species of coralgobies we could find. We had to wait until spring to get started. When the time came we headed back to Indonesia, primarily Raja Ampat, Lembeh Strait and the Banda Sea. 

In Raja Ampat, Yan Alfian our guide of long standing aboard the Dewi Nusantara took to goby hunting with gusto. Once underwater, and into the mission, we were delighted to discover that coralgobies were more common than supposed, and even more surprising, inhabited depths down to 25 meters. However, inshore coral thickets, from the surface to four meters, consistently proved to be our most bountiful hunting grounds. Unlike the isolated mated pairs living in Ambon, we often encountered clusters of the same species living on a single coral head, while other colonies accommodated multiple species.

From day one, lessons learned in Ambon served us well. Notably, we never again ventured into the shallows except on rare days when the winds and surge settled and the inshore water calmed to a glassy sheen. We typically limited our search to small corals a foot or two across to minimize the area where the gobies could hide, and only worked colonies surrounded by sand—essential etiquette for diving in a fragile universe. After finding a species of interest, we immediately set about looking for a breach in the branches leading to perching places. If not found, we quickly moved on. Frequently a dozen or more inhabited colonies were inspected before a potential opening was found. Besides a clear view, these unrestricted passages allowed my single strobe’s beam to reach the subject without creating harsh shadows.

The tedious task of wrangling one-inch gobies on their home turf requires cunning, dexterity, determination, and patience galore. Once Yan selected a target, he began shooing the goby in my direction. These cat-and-mouse competitions could take the better part of a dive to complete. My part in the game was limited to holding focus on a vacant perch while Yan’s worked his magic.  

The taxonomy of reef gobies is far from complete. Currently around 30 Gobiodon, and less than ten closely related Paragobiodon species from the western Pacific, Indian Ocean and Red Sea have been scientifically described. Fieldwork and photographic evidence suggest a significant number of species remain undiscovered and undescribed. Our amateurish attempt at species hunting logged 12 described Gobiondon and six Paragobiodon species from Indonesian waters, along with a single undocumented Gobiodon from Lembeh Strait and a lone mystery Paragobiodon found living outside Ambon Bay. A number of photos from our efforts currently adorn the coralgoby section (pages 332-335) of Reef Fish Identification—Tropical Pacific

Five-lined Coralgoby, Gobiodon quinquestrigatus
Five-lined Coralgoby, Gobiodon quinquestrigatus
Blackfin Coralgoby, Paragobiodon lacunicolus
Blackfin Coralgoby, Paragobiodon lacunicolus
Black Coralgoby Paragobiodon melanosoma
Black Coralgoby Paragobiodon melanosoma

A Short Origin Story

It would seem that such a small, simple life, lived out within such small, simple surroundings, would be simple, but like everything else in nature it’s delightfully not. And indeed, like all other forms of life studied extensively coralgobies also have an enchanting story to tell. Their history, driven by an irrepressible itch to fill a fertile ecological niche—in this case shallow coral gardens—began long ago in a forgotten time. The drawn-out quest powered by the adaptive forces of natural selection eventually came to pass.

While most small, short-lived members of the extensive Gobiidae family build burrows or rely on hiding holes for protection, coralgobies limit predation by living exclusively within the tightly knit networks of fast-growing, sun-worshiping, shallow-water branching corals. Adding an extra layer of protection, the scaleless, mucus-laden skin of many species contains clusters of poison cells. And, like other gobies living in high-current habitats, the coralgobies’ two ventral fins have grown together and developed small suction cups to hold them securely in place during blustery conditions. 

As partial compensation for their hosts’ protection, coralgobies help keep polyp-nipping butterfly fishes at bay. In a paradoxical twist: Stomach analysis of field-collected specimens indicates a primary diet of both free-swimming and parasitic copepods (tiny, shrimp-like crustaceans), supplemented with a healthy portion of purloined flesh from their coral hosts.   

Sex change (hermaphroditism) from female to male (protogyny) and to a lesser extent from male to female (padandry), is frequently employed to help stabilize social structures of fish populations, primarily in the wrasse, sea bass, anemonefish and goby families. Aquarium experimentation in the 1990s revealed that coralgobies have the unconventional ability to change sex more than once (bi-directional sex change) during their lifetimes—the only group of reef fishes presently known to do so. The norm-breaking lifestyle to improve reproductive success appears to be an artifact of isolation. Researchers studying the social structure and sex life of a natural population of the common Red-barred Coralgobies, G. histrio on the Great Barrier Reef uncovered several other surprising nuggets of interest. 

Broad-barred Coralgoby, Gobiodon histrio
Broad-barred Coralgoby, Gobiodon histrio

Detailed surveys of the study area determined that more than 80 percent of the platter-shaped plate corals, Acropora nasuta, was occupied by either a single immature female, or a mated adult pairs. This led the authors to speculate that settling larvae and adult immigrants from surrounding colonies were driven away from the established breeding grounds of territorial pairs. This dominant control of prime real estate left only a small numbers of vacant corals, or those inhabited by solitary immature Red-barred residents, open for colonization. Under these limiting circumstances the ability to change sexual orientation in either direction increases the likelihood of a vagrant of either gender forming a breeding pair.

After establishing control of a coral head, mated pairs, which in this case were found to be equal in size and able to maintain long-lasting bonds, turn into breeding machines. For four consecutive days males guard egg patches laid by their mates at the bases of branches nipped clean of polyps while their progeny mature. Only a day or two after hatching females deposit another fresh clutch for safekeeping. This ongoing reproductive cycle continues uninterrupted throughout the breeding season.

Without a doubt coralgobies’ most amazing evolutionary adaptation enables the little fish to remain inside their coral homes even when they become high and dry during annual spring tides. It is believed that coralgobies can survive for up to four hours out of water by an adaptation unique to the group. As the water level drops resident gobies nestle in the shade of branches and begin circulating a small volume of water through their mouths and over the gills’ blood-rich lining where oxygen is absorbed. Depleted, the droplet flows outside the gill cover and through an exterior groove distinctive to the genus, spanning the length of the lower jaw. During the transit the water is oxygenated through the diffusion of air before entering the mouth and making its way back to the gills where the cycle begins once again. The intake of oxygen through the skin might also play a role in the remarkable feat.

A Matter of Color

To advertise their poisonous nature the majority of coralgobies wear brightly patterned wardrobes—a strategy common to many colorful terrestrial and marine species. However, a few coralgobies in both genera buck the trend by displaying drab monotone colors to the world. It’s possible that these lackluster species, such as the Black Coralgoby, P melanosomus (pictured above), lack poisonous tissue, but no one knows for sure. 

From personal observation, the Golden Coralgoby, P. xanthosoma, or (Should the common name be Emerald Coralgoby?) has the ability to change their color back and forth between yellow and green in a matter of minutes. For whatever reason, no one yet knows. The little illusionists live exclusively in mated pairs within Birdsnest Coral, Seriatopora hystrix. These densely branched shallow-water hideaways create such inaccessible strongholds that I put off photographing the species for months. My reluctance took a turn in Raja Ampat when an irresistible yellow face peeking out of the branches caught my eye. After downloading my images, a yellowish head generously tinted with green splashed across my screen. At the moment I blamed the anomaly on Photoshop, and left it at that.

We were back in Ambon during a stopover between voyages when Golden Coralgobies next came to mind. During our brief visit we had an opportunity to explore the inshore shallows on the far side of the bay for the first time. Four feet deep and thick with coral from sand to the surface, the reef epitomized goby terrain, but Anna was nowhere to be found, off with the guide working on another one of her many esoteric projects I reckoned. Fortunately, there are so many gobies around that I could find them for myself, and most just happened to be Golden Coralgobies. In fact, the species was so abundant I decided to put some effort into getting the long postponed ID-shot. 

I concentrated for the better part of an hour on a single coral head sheltering a bright yellow pair. Seldom on their perch, the occupants I was tracking kept on the move deep within the branches. While investigating the routes of their convoluted runs I noticed one of the gobies occasionally taking a shortcut through an exposed gap on the coral’s outer edge—not much of a chance, but a chance nonetheless. Each time the goby raced through the opening I snapped the shutter. Glancing down at the screen between shots I noticed an ever-darkening flush of green spreading over the goby’s yellow coat. By the time Anna and the guide returned with the boat the once Golden Coralgoby had transformed into Emerald Coralgoby extraordinaire. 

Golden Coralgoby, Paragobiodon xanthosoma
Golden Coralgoby, Paragobiodon xanthosoma

Another question about color change has to do with Lemon Coralgobies, G. citrinus—at two-and a-half inches one of the largest coralgobies around. Mated pairs and small groups of these giants among their kind set up housekeeping inside large open Acropora colonies where they boldly perch out in the open on the ends of branches exhibiting marked indifference to passing divers. One would suspect that their bravado had something to do with being somewhat large in a Lilliputian world, coupled with poisonous tissue, clearly broadcast to predators by their bright color. This makes one wonder: If this wonderful eye-catching adaptation is so effective at warning away predators, why would Lemon Coralgobies engender a black variation? Also after scanning goby literature, it never became clear whether black individual are immutable, or like the Golden Coralgoby have the ability to change their color at will. Seems like another mystery remaining to be solved by an inquisitive aquarist, a savvy underwater naturalist or an overworked graduate researcher, or a combination of the above.    ~ Ned DeLoach


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