Skip to content

Stories from a Coral Reef – Cleaner Fishes and Early Days at Heron Island


This is another in my series of stories from a coral reef – stories in which I seek to tell about the wonders of this marvelous world, and what it has been like as a scientist trying to uncover just a small part.

Daily Life on a Coral Reef

The sun was coming up and the dappled light was getting brighter across the sandy floor outside his shelter. It was time to start a new day with a visit to his Number One Wife. He stretched, flicked his fins a couple of times, swam out of his shelter across the sandy patch and began to move along the reef edge as he always did. Neighbors of various types were out and about; he noted each in passing, but he was on a mission.

Number One Wife held court just round the next bend, and he readied himself. It was necessary to be maximally assertive on first meeting her; she had to be kept in her place. Rounding the corner, he saw her, and rushed forward, fins erect, head slightly down. She lowered her fins and turned away. Again he rushed her, again she demurred. Once more should be enough for now.

Labroides-dimidiatus Keoki Stender
Labroides dimidiatus, the bluestreak cleaner wrasse. Photo © Keoki Stender

A client was hanging about nearby, so the two of them stopped their friendly aggressivity, and went into action, performing the sultry vertical rolling ‘dance’ as they approached. The client, a large coral trout, Plectropomus leopardus, rolled almost onto his side, raised all his fins and waited motionless for the coming caresses. Swimming rapidly along the flank of the larger fish they made sure to make frequent, delicate, physical contact, while periodically nipping at parasites and loose bits of skin. Leaving Number One Wife to investigate the rich opportunities along the base of the dorsal fin, he moved to the mouth, which the coral trout obligingly opened. Cleaning around the larger fish’s teeth, he swam in, and through the gills, out the operculum. Such intimacies continued for a minute or so, when the coral trout flicked its dorsal, righted itself, and moved away. They attended to a couple more clients, before it was time to move on. He needed to visit each of his other wives. And then repeat the whole exercise several more times during the day. He headed off along the familiar path to Number Two Wife.
Labroides dimidiatus & Plectropomus image_full J Fatherree

Cleaner fish getting ready to enter the mouth of a coral trout.
Photo © J.W. Fatherree

I do not, for one moment, believe that the cleaner wrasse, Labroides dimidiatus, verbalizes its thoughts, even internally, in this degree of detail. But nor do I believe that fishes are colorful automatons that carry out sequences of complex behavior as simple responses to external stimuli. These fishes, at least, have some vague fishy awareness of their environment and the other living creatures in it. They may, like me, treat the corals as simply the architecture of their world, but they recognize the fish, crustaceans, molluscs, and other mobile creatures as living entities, and often as neighbors.

I cannot know that the cleaner wrasse is quite that aware, but I find it hard, having watched cleaner wrasses many times, to believe that they are not. From the first time I put a mask and snorkel on and stuck my head into the world of a coral reef, I have always been aware that we are mere visitors to neighborhoods filled with creatures of many species, who have busy lives, and who know many of their neighbors as individuals, even if they do not sit down to coffee at the local Tim Hortons or Starbucks. The cleaner wrasse, of all reef species, deals intimately with numerous individuals of other fish species during the course of its day, and while it may not recognize its succession of clients as individuals, I’ll bet it recognizes some of them that way. And they, him. Or her, since the great majority of cleaners are females.

Two Hawaiian cleaners, Labroides phthirophagus, attending to the needs of a Novaculichthys taeniourus wrasse. Photo by Brocken Inaglory via Wikimedia Commons.

I had seen the Hawaiian endemic cleaner, Labroides phthirophagus, during my graduate studies, but I first met Labroides dimidiatus and learned just how complex its life was, during my first years in Australia, when, as a young faculty member with limited research funds, I was struggling to build a research career doing field work at Heron Island.

Heron Island, Low Isles, and early Australian reef research

The Heron Island Research Station was the first ‘permanent’ research facility established on the Great Barrier Reef, having been cobbled together by the Great Barrier Reef Committee with minimal finances in 1951. The Great Barrier Reef is mostly a long way from shore, and there are remarkably few islands out on the reef itself. The southern end of the reef is well north of Brisbane, in 1951 the only significant city in Queensland and home to the most northerly Australian university. True, there had been limited research on the Great Barrier Reef prior to 1951, but it had been done by expedition, and with difficulty.

The greatest expedition, of course, had been the 1928-1929, year-long expedition to Low Isles, just north of Cairns and close inshore. That expedition is variously known as ‘the Great Barrier Reef Expedition’, or ‘the University of Cambridge – Royal Society Great Barrier Reef Expedition’. It was funded mostly with UK money, although the Great Barrier Reef Committee had raised some money for it, and half a dozen Australian scientists were allowed to participate as ‘junior partners’ to the Cambridge team – such were the ways of Commonwealth science collaboration in the colonial past.


GBR expedition team nla.pic-vn4274584-s1-v
Members of the Great Barrier Reef Expedition at Low Isles. C.M. Yonge is the man seated front, center, in long pants. His wife is to his left. Photo is part of Yonge, C. M. (Charles Maurice), 1899-1986. Album of the Great Barrier Reef Expedition in the Low Islands region, Queensland, 1928-1929, National Library of Australia.

The Low Isles expedition brought the young Yorkshire-born, Scottish-educated C.M. Yonge (later to become Sir C. Maurice Yonge) to Australia at the age of 27 as expedition-leader. He was an invertebrate physiologist and experimentalist rather than a taxonomist, the more typical biological expedition leader of those times. The UK team had limited tropical experience so they certainly brought fresh eyes to a largely unknown ecosystem. The results of the year at Low Isles were published in seven volumes between 1930 and 1968 and contributed significantly to our understanding of coral reef ecosystems. Quite significantly, despite the fact that SCUBA had not been invented and these scientists worked by wading at low tide, by peering through glass-bottomed boxes, by using downright dangerous-looking helmet diving, and by dragging, hooking and trawling for things down below.

net and diver GBR expedition
Collecting at Low Isles: Dr. F.S. Russell with large, coarse-mesh tow net used to capture small fish and larger invertebrates, and an unknown, but intrepid diver, modeling the surface-supplied helmet. Both photos part of Yonge, C. M. (Charles Maurice), 1899-1986. Album of the Great Barrier Reef Expedition in the Low Islands region, Queensland, 1928-1929, National Library of Australia.

They provided a benchmark for our understanding of how reef ecosystems functioned ecologically that was only really extended when the Odum brothers, Howard and Eugene, did their pioneering work at Enewetak Atoll, in the Marshall Islands in the early 1950s. After 1929, Australian reef science remained very quiet until well after the establishment of the Heron Island Research Station, apart from some continued interest by geologists in drilling to see if Darwin had been right about how reefs grow. How times have changed!

Heron & One Tree 2008 048 small
Heron Island in 2008. The research station is the cluster of buildings to the right of center. Buildings to the left are the resort, a much more sophisticated place than it was in 1969. Photo © P. Sale

But back to Heron Island, which, come to think of it, I first visited when I, too, was 27 years old (only I came alone, and not for a full year’s stay). At the end of the 1960s, Heron Island remained the only site set up to support research on a part of the reef well out from shore (it is situated about 100 km north-east of Gladstone, Queensland). It was a decidedly primitive place: modest houses for the Director and the Maintenance Officer, Kitchen-Dining Room, toilet-shower complex, about 10 two-bed sleeping huts, the laboratory building, a sea water tank and aquarium facility, and one research vessel. Sounds not too bad. Except that the laboratory was devoid of equipment, the aquarium facility had only two functional aquaria, the sea water system only operated at high tide, and the research vessel, called the ‘dory’, lived up to its name.

The dory was an in-board powered, high-sided, heavy, wooden tender about 4.5 m long, with a 1-cylinder, gasoline motor that was started by rotating the flywheel as fast as possible with your bare hand before disengaging the clutch. It would then putt-putt along at a stately 1 knot. Getting into it with dive gear on involved first having to have remembered before you got in the water to leave a line hanging over the gunnel on which to tie the dive tank (I learned this lesson the hard way). Then, having completed your dive, you took off your tank and tied it to the line, threw your fins high over the gunnel, and clambered up onto the rudder, in order to be able to climb over the stern and fall into the boat. Hopefully, you then remembered to reach over and haul in the dive tank.

Fresh from the University of Hawaii, which included the Hawaiian Institute of Marine Biology (HIMB), a well-equipped modern laboratory with several Boston Whaler work boats, on a small island in Kaneohe Bay, I at first missed those things that Heron Island did not have. But by the end of my second visit, and once I got my own boat so I no longer had to deal with the dory, I knew that Heron Island had one immeasurably important advantage – easy access to a very rich coral reef where it was possible to do field experiments that told far more about how reefs functioned than any aquarium experiment ever could. And I found myself thinking all those scientists who worked at HIMB, and tended to go out to the bay simply to collect organisms to bring back to the lab, were missing out on one of HIMB’s great secrets – its own easy access to a large, coral-rich bay that they could learn about by doing field experiments too. (Kaneohe subsequently degraded somewhat, as stormwater run-off from the mainland over many years built up nutrient levels in the water leading to dense growths of nuisance algae, but when I was there it was a place of numerous, moderately rich Hawaiian patch reefs.)

Despite the primitive lab facilities when I first visited, Heron Island offered easy access to an incredible natural laboratory – a living reef where one could do field experiements to find out how the system worked. Photo courtesy of Tourism Queensland.

The Heron Island Research Station did have a small library, a vital resource in those pre-internet days, with useful books that gave you long out-of-date names for the fishes, and even less useful names for the corals (an out of date name is better than no name at all). It also held an eclectic collection of curious volumes that helped fill a rough and windy day with tales of expeditions in the south seas or, one of my favorites, a slim volume written as advice to a young acquaintance about to depart from England for ‘the colonies’. It was written in the 1920s or perhaps slightly earlier by an author who had been posted to British India as a medical officer, and who boasted more letters after his name than were in the name itself. It contained useful information about avoiding chills, which apparently caused everything from diarrhea to malaria, by wearing a cummerbund of ‘stout muslin’ at all times. It had a chapter on the importance of always dressing for dinner, even in the most primitive field conditions, because it was important to maintain standards. And it provided stern admonitions to avoid interactions that might lead to fraternization with the native women because of risks to one’s reputation as a gentleman, and undescribed but hinted at medical issues most dire.

It was at Heron Island that I first saw the amazing photographs of the Great Barrier Reef, taken by William Saville-Kent in the 1890s and printed in a large-format, glorious volume that now speaks of a long-ago time when the Great Barrier Reef really was great. The Heron Island library also led me to become interested in James Cook’s journals. The library did not include the journals, but sparked by something I read there, I searched the three thick volumes out in the library of University of Sydney, and read them voraciously. (Those really were the good old days, when a faculty member had time to do irrelevant things like reading James Cook’s account of his journeys.)

It was also at Heron Island that I first encountered a kerosene refrigerator. I marvel to this day that you make a kerosene fridge colder by turning up the flame underneath it. Or that you deal with a kerosene fridge that appears not to be working by emptying the contents, and turning the whole thing upside down for 24 hours. Chances are that once you right it, and re-light it, it will work again. Don’t ask me why. These are facts that come from a parallel universe in which kerosene can help keep your food fresh.

Getting to Heron Island, in my early days, was a lengthy, often times tedious process. With insufficient research funds to fly, I used the train. This meant overnight to Brisbane, cool ones heels in a convenient pub for the whole day, and overnight to Gladstone. There were/are no through trains because Australian states have used their freedom from any national mandate to select different track gauges for their railroads. The train from Sydney terminates in Brisbane because all tracks north from there are narrower. Once I got to Gladstone – now a far, far larger coal, LPG and alumina export terminal than it was then, and site of some of the dredging and expansion that now threatens the Great Barrier Reef – there was more heel cooling before boarding the launch to Heron Island.

Gladstone ca 1975 PC1229
The main street of Gladstone about 1975. Walking up and down this street for a Saturday morning whiled the time away, and left one better able to face the launch journey to Heron Island than did spending the morning in the cool dimness of one of the many pubs. Photo © Centre for the Government of Queensland, University of Queensland.

The launch service was provided by the Heron Island Resort, in those days a decidedly down-market affair with salt-water showers, grub rather than cuisine, and a clientele including lots or repeat visitors from around Australia, mostly going for the fishing. ‘Launch’ was a kind description. One of my favorites of the succession of launches I experienced over the years, was the ‘Saramoa’, a ship which moved pretty well the way her name sounded – a gentle, forward roll, shifting towards the starboard with a noticeable corkscrew motion, and then abruptly finishing with a rapid, rightward swash of the stern, all repeated, once every five seconds, for the seven hour crossing (on a good day). I learned to stand rather than sit, to position myself forward of the funnel and its nauseous diesel fumes, and to keep my eyes firmly on the horizon, while ignoring the mayhem behind me aft to the stern. At Heron Island, the tourists would be helped across the shallows, looking much the worse for wear, and up the beach, to collapse in their cabins, while we scientists were left to find our way across the island to the research station.

Our food, ordered in advance from the Gladstone supermarket, would get delivered from the launch by tractor, in cardboard boxes variously soaked with seawater and falling apart, and would have to be sorted out, and packed into the limited fridge space. With experience I learned how to order a week’s food at one time, and to order items that would last through the journey and the vagaries of kerosene refrigeration. Giant Queensland cabbages and pumpkins would last forever. Lettuce, not so well. Eggs were a gamble, but usually worth it. Canned food which had lost its labels during a rough crossing could provide unexpected delights. UHT milk tasted far better than canned milk or powdered milk, although powdered whole milk had a special taste that could become mildly addictive on a tropical island. A large leg of lamb that started out frozen could endure all sorts of misadventure en route and arrive in pretty good condition ready to be roasted, and ordering same marked you as ‘not a tourist’. It also led to interesting communal meals with other researchers, some of whom were from far away, just passing through, getting an inexpensive look at the reef while in Australia. Many people who became long-term friends, colleagues and collaborators were first met on Heron Island.

The Great Barrier Reef Committee was a decidedly strange organization. I know because I was a member over several years, and with Hal Heatwole and some others, metamorphosed it into the Australian Coral Reef Society, which holds annual scientific conferences and supports reef science and conservation in other ways. (Its first scientific conference was convened at University of Sydney in 1987.) When I first encountered it, the Great Barrier Reef Committee was made up of scientists who genuinely believed that Australia had a responsibility to advance reef science, but who had trouble agreeing with each other about how to do that.  They convened the second International Coral Reef Symposium (now a major, quadrennial conference) as a week-long conference on an aged cruise ship that sailed from Brisbane up to Lizard Island and back with field trips along the way – a bizarre experience fondly remembered by those of us who participated.  And they struggled to keep the Heron Island station alive, with never enough funding, and with a misguided policy of hiring directors who were supposed to do research, but were left marooned on a tiny island, remote from academic stimulation, through long hot summers when mosquitoes, mutton birds and noddy terns helped make life difficult each in their own way.

Mutton birds resting quietly a few meters from their burrow on Laysan Island, leeward Hawaiian Islands. I don’t remember the Heron Island birds ever resting quietly! Photo © Ian Thomas

Mosquitoes do what mosquitoes the world over do and none of the buildings were screened. Noddy terns, which seem quite attractive at first glance, nest in the trees, gluing leaves together with excreta to make some of the worst engineered nests in avian history. In wet weather the trees drip excreta and hatchlings slide out of the nests to their death on the ground below. Mutton birds, or wedge-tailed shearwaters (Puffinus pacificus) are something else entirely. They breed on Heron Island in the summer months, digging burrows in the sandy soil instead of building nests. They are pelagic feeders and one member of each pair spends the day out at sea foraging while the other sits on the eggs in a burrow that can be used over many years by the same pair. Once the eggs hatch both parents spend the day feeding, returning at dusk to regurgitate delicious, partly digested squid for the young. (I know this because one summer I was living in a new hut that was on one bird’s flight path to its burrow. Every evening at dinnertime it slammed into the wall of my hut, staggered in and deposited its squid on my floor, shook its head a couple of times, then staggered out and wandered off on foot to its burrow.)

Mutton birds sing. All night. Caterwauling does not begin to describe the music. They wail and moan and sigh. Sometimes it sounds vaguely orgasmic; other times more like torture. Think cats in heat, only all around you, and loud. The volume rises and falls as different birds join in. Sleep is best achieved with copious quantities of beer, wine, or rum just prior, available at a price at the resort if your own stash runs out. The trick is to fall asleep quickly, and stay asleep, because once woken it is difficult to go back to slumberland.

Of course, mutton birds are beautifully acrobatic in flight, and they summer in the far northern hemisphere. In fact the parents leave Heron to migrate north about two weeks before the young have fledged. Fat, roly-poly nestlings emerge, bewildered, from their burrows and amble about the island, getting thinner and better able to fly. And then, one day, they take off, heading north to the summer range. How they know where to go, I do not know. But these features almost make me want to marvel at mutton birds, instead of hate them for their singing.

Anyhow, back to the plight of research station directors. Abandoning a research scientist on a tiny tropical island, and assuming he (they have all been male) will remain productive was not a sensible plan. The first one I met was Peter Woodhead, a British fisheries biologist with significant past achievements, who had converted to investigating coral biology, and helped me a lot in my early struggles to sort out the myriad species of corals on the reef. When he finally left the island, however, Peter had clearly been driven ‘tropo’ by his experiences; he proceeded to throw most of his possessions overboard on the long slow launch journey back to Gladstone. I never saw him again.

In 1970, the University of Queensland became a co-owner of the research station; in 1980 it became sole owner and began to make significant investments. Today the station is a maze of new buildings and complex equipment where real science, sometimes important science, gets done, and the current Director, a former undergraduate of mine, spends much of his time on campus in Brisbane. But I’m getting ahead of myself, because I was talking about cleaner wrasses, and that is a story from 1969.

Ross Robertson and the Cleaner Wrasse

In my early days in Australia, I was spending about three months a year at Heron Island, typically as three, month-long visits. Among the other ‘regular’ visitors there were several that stand out, and one of these was D.R. (Ross) Robertson. In 1969, Ross was a PhD student at University of Queensland. He was studying the social behavior of the cleaner wrasse, and spent far more time than I did at Heron Island. Consequently we frequently overlapped, talked about what we were doing, and learned from each other.

It’s my belief that Ross had taken on a major burden that he did not have to carry; he had decided that he had to build a bigger reputation in Queensland reef science lore than had Howard Choat, who had preceded him as a UQ graduate student working on fish at Heron Island. I do not necessarily mean become a better scientist, I mean build a bigger persona, and Ross had his task cut out for him, because Howard is still talked about — admiringly, incredulously, enviously, derisively, sometimes affectionately — by many scientists he has come into contact with over the years. (I count both Ross and Howard as friends.) Howard was arguably the first reef scientist to use SCUBA to do field research on the Great Barrier Reef. Howard was also given to bouts of unusual behavior usually involving chemical substances and/or nudity when he was not doing serious, hard work. Howard did foundational work on reef fish feeding ecology, and had a career, post-PhD, that took him ultimately to a Professorship and the Chair of marine biology at James Cook University, where he built a department second to none in Australia. He still gets into the field, chasing big fish to spear, so he can look at their mouths and their stomachs. As a graduate student, Howard carved out a niche that Ross sought to fill.

So Ross, who was all short back and sides when I first met him, grew his hair long and unruly, explored chemical substances (it was the 60’s after all), mostly refrained from public nudity, and dived into his research with a passion I have seldom seen since. At one point, he was spending so much time in the water watching his fish that his hair and beard began to take on a greenish tinge – he fixed that with a bit more liberal use of shampoo. And as happens when someone is deeply immersed in his science, he became silent, uncommunicative, reflective for days at a time, only to become maniacally cheerful and ready to party a day later. In short he became a lot like any scientist trapped on a tropical island with noddy terns, mosquitoes and mutton birds for months at a time, except more so. And in the midst of all of this, he discovered some amazing things about the cleaner wrasse and proved his talent as a scientist.

Ross approached the cleaner wrasse in much the same way Jane Goodall approached chimpanzees, except under water. He got in the water, for hours at a time, getting to know individual fish by tiny differences in their color patterns, and following them around recording what they did. He made crude maps of the reef on plastic slates and traced the paths fishes followed over the topography while scribbling notes about what they seemed to be doing. He taught me how to sharpen a broken pencil using your thumb nail (when the pencil wood has become softened by several hours in salt water, thumb nails can work well, and you don’t have to go back to the boat for a replacement pencil). The cleaner wrasses really did have paths – trails that they followed repeatedly, day after day, as they moved about the reef. He discovered that larger fish moved about over larger areas, and that the largest fish in any area was always a male. He found that males moved over their large territories seemingly looking out for neighboring males, and displayed aggressively when they saw one. They were advertising their presence and defending their territories.

Ross discovered that smaller fish had smaller territories nested within the male’s, and were all female. But they defended their own territories from other females of similar size, while tolerating smaller females who set up their own smaller territories within. The social group consisted of a large male with a large territory defended from neighboring males. Within that territory were a series of smaller sites defended by smaller females from other females, with still smaller territories of still smaller females within. This is a classic haremic social system, a novel discovery at that time, but now known in a number of other fish species.

Ross also found that within the male’s large territory there would be two or more sites at which cleaning behavior was most likely to occur. These cleaning stations were attended by whichever members of the social group had territories that happened to coincide at them. The fish would cooperate in cleaning client species, and client fishes would come to the cleaning station, sometimes many times a day, to be serviced. Sometimes client species would line up, patiently waiting to be cleaned. The amount of communication going on to permit this high level of spatial and social organization within the group of cleaner fishes and among them and the client fishes of many species has to be impressive. It’s all done with subtle flicks of the fins, arching of the back, changes in orientation, and it functions as smoothly as any social activity among a group of humans. Only the mix of species makes it more like that bar in Star Wars.

Star Wars Cantina
Chalmun’s Spaceport Cantina, or Moe Eisley’s Cantina, was a popular spot on Tatooine for a wide range of species. Photo ©

The major discovery of Ross Robertson’s PhD research concerned those visits from the male to each of his females, and the aggressive displays that occurred. There is a reason why the largest fish in a group is always a male, and why all the smaller animals are female. Like a number of other reef fishes, the cleaner wrasse is a sequential hermaphrodite, or, to be more precise, a protogynous hermaphrodite, which simply means an animal that is first female and then male. At the time Ross was working there was limited understanding of how sex reversal occurred, and what triggered or postponed it. Ross wondered if the regular visits were part of the explanation, and being an experimentalist at heart, he set out to poke the system to find out what would happen. He killed a series of male cleaner fishes using a very small spear propelled using a rubber band between his fingers. Being Ross, he practiced until he became devilishly accurate. After removing a fish he then watched, waited, observed and recorded.

So, what happened? Ross discovered that when he removed a male cleaner wrasse the social system reorganized very swiftly. In the article he published in Science in 1972, he wrote

“For approximately half an hour after the death of the male the dominant female continues to behave aggressively as a normal female. This simple female aggression then wanes to more neutral reactions to nearby subordinate females. Approximately 1½ to 2 hours after male death, maleness appears ln the form of the special male aggressive display that the new “male” starts performing to the females of its group. The assumption of the male aggressive role can be virtually completed within several hours, when the “male” starts visiting its females and territory borders. The switchover to male courtship and spawning behavior takes somewhat longer but can be partly accomplished within 1 day and completed within 2 to 4 days. Other individuals also respond within a couple of hours to the altered social situation created by male death; low-status females take over vacant female territories, and neighboring males invade and attempt to take over the territory and harem.”

The sudden lack of visits by her male, with his special male aggressive displays, triggers hormonal changes that allow the largest female to begin to change sex. Within 2 hours, she has taken over his role and is performing the male aggressive displays to the other females of the group. Within as little as a day she can be performing as a male in courtship and spawning (although it takes 2-3 weeks for viable sperm to be released). Ross also found that the loss of a male did not always lead to sex reversal and a smooth reassignment of roles. Sometimes a neighboring male, noticing that the neighbor is no more, is able to take over the harem, adding those females and the new territory to his existing social group, and preventing the largest female from changing sex. He even described one case where a dominant female began showing the male aggressive display, was then forced back into a female role by the neighboring male who attempted to take over, but then resumed male behavior and forced the neighbor male to back off. She ultimately became a fully functional male at that site.

Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus Wikimedia commons
Two Labroides dimidiatus cleaning a larger potato cod, the grouper, Epinephelus tukula, at Osprey Reef, in the Coral Sea. Photo © Richard Ling via Wikimedia Commons

Ross Robertson’s work was the first discovery of the way in which the playing out of a social behavior – the male aggressive display – can suppress sex reversal in a female otherwise primed to change sex. Not all protogynous hermaphrodites have sex reversal controlled by behavior, but we now know a number of other protogynous fish species do.

Ross Robertson moved on from cleaner wrasses after completing his Ph.D.  He went to a post-doc and ultimately a long and successful career as a tropical fish ecologist, biogeographer and systematist based at the Smithsonian Tropical Research Institute in Panama where he is busy today seeking to unravel more mysteries of the fishes of coral reefs. Work on the cleaner wrasse by other people has revealed many more amazing facts: Their feeding activities substantially reduce the external parasite load on other reef fishes. Preventing access to cleaners can raise parasite loads on a client fish five-fold in a day. Cleaner fish use gentle tactile stimulation with their pelvic fins to calm client fishes and make them receptive. And cleaner stations are places where clients waiting to be serviced experience less aggression from larger piscivorous clients that are also aggregating to be cleaned.

If there were no cleaner fishes, we probably would not be able to imagine their existence. If Ross Robertson had not taken the time to get to know and understand his cleaners we might never have known how intricately the social system – including the social connections to all those client species – of this species is, and other scientists might never have wondered about the role these fishes play on a reef. (Indeed, I despair that far too many young reef scientists never take the time to immerse themselves in this amazing ecological system. They focus instead on the specific steps that they need to take to get the measurements to test the hypothesis that funded their field trip, and fail to look around to discover something really new.)

The world is full of amazing creatures, and equally amazing ecological and behavioral interactions that knit them all together. Coral reefs are particularly rich but other systems have their surprises waiting to be discovered as well. Unfortunately, we seem to be doing our best to reduce diversity and simplify ecological systems. If we continue, we will create a planet which is far less wonderful than the world we have grown up in. I don’t think that is a good world to pass to our grandchildren. I want them to be able to watch cleaner wrasses and wonder about what those little fishes are thinking.