Article © Julian Dignall, uploaded January 31, 2020.

Different parts of the same river
Having returned from our three-day expedition upstream to the pleco laden Cachoeira Grande ("big falls") on the Rio Iriri with a touch of sunburn, not inconsiderable insect bites and ear to ear smiles; a slow morning in Altamira had me considering what other memories awaited as I worked with those already stored in my camera. I had learned that the Xingu had so many facets to it that while I could describe it with pictures, the vast scale and seemingly endless variability of the river was a struggle to comprehend and coherently explain. Across the channel from Altamira, the Isla do Arapujá was struggling too. Today, this river island was in the final stages of being bulldozed and much of the vegetation already pulled up was ablaze. This effort being carried out to minimise the amount of vegetation that would be submerged when the Belo Monte dam was operational. Submerged vegetation rots and produces a lot of methane, but I couldn't help thinking that burning it was not much better. As the flames rose, to several meters in places, we also lost the habitat of Plesiolebias altamira, a killifish endemic to the island. This denuding of islands within the huge range of the proposed dam reservoir is being carried out without any wildlife rescue. This includes endemic fishes.

• The Isla do Arapujá on fire. Government workers bulldoze and burn all vegetation. This and many other islands will be flooded by the dam reservoir
• One of the countless islands showing normal waterlines drawn by mother nature on her rocks. And nothing on fire.

Therefore, this whole trip was a sweet and sour experience of seeing such a dazzling array of amazing fishes many of which we've enjoyed for decades as ornamental fishes and have supported many families locally in this sustainable Fairtrade. Yet, sour because I was there at the point of no return. Future generations would not be able to witness this place as I and others before me have because of the irreversible impact of the Belo Monte dam. Sobering stuff but I was travelling in experienced, knowledgeable and light hearted company. Of course there were the ichthyologists, Leandro Melo de Sousa and Mark Sabaj Perez, leading lights in a team of researchers primarily at The Academy of Natural Sciences of Drexel University (Mark's institution), Texas A&M University, Instituto Nacional de Pesquisas da Amazônia in Manaus, and Universidade Federal do Pará (Leandro's place of work) in Altamira. Also keeping spirits high was legendary fish importer Oliver Lucanus who never missed an opportunity recount tales of high adventure seeking out new ornamental fish species across the globe. Travelling with Oliver were Drs Margaret Kalacska and Pablo Arroyo from the Department of Geography at McGill University in Montreal. While Leandro and Mark are ichthyologists and you'd expect them to work on the river, but Margaret and Pablo brought something new to our travels. They'd recently been to Northern Tanzania (Lake Natron, Chemka Springs and Lake Chala) with Oliver and used airborne drone technology and satellite imagery to record and map the terrain from the sky. Their work showed a chronology of land use and environmental changes putting pressure on endemic cichlid habitats. While my "PlanetXingu" charity fundraiser had funded such a drone for Altamira University, to have it augmented by such high-end kit and expertise for this trip took us to another level. Margaret's interest in remote sensing is in mapping aquatic ecosystems from the air to determine habitat extent and change from the images while Pablo, an ecologist, is interested in mapping species diversity.

Mapping the same area at different times can show us how much habitat is lost or gained over time and how the landscape around the aquatic ecosystems changes. Land cover and land use changes such as deforestation, agricultural land expansion, urban expansion and human activities such as water abstraction have significant negative impacts on the aquatic ecosystems. The drone imagery can provide real-time monitoring of freshwater fish habitats while at larger scales satellite imagery shows us an unbiased historical assessment. In the specific case of the Xingu, much of the areas being mapped would be inundated by the mega dam reservoir or would be either dried or greatly diminished as the course of the water changed. Pablo, Oliver and Margaret's research (Fish + Forest Project) generates tools that are readily deployable in the field at low cost, allowing for the ongoing monitoring of habitats crucial to the survival of specialized endemic fishes. Their goal is to determine the amount of endemic Xingu fish habitat that will be lost as the mega dam reservoir is completed.

Satellite images and describing what we see
Photo credits for these sets of images belong to the United States Geological Survey - they're natural colour representation from the Landsat 8 OLI sensor. They show dark green for forest, light green for deforested area, dark blue for water and light colours for construction / bare earth.

• 2011: Although dam construction is well underway, there is no change to the river as is flows into the Volta Grande, known colloquially as the "big bend" downstream of Altamira (just off to the left). The complexity of the river as it splits into many channels around this section is illustrated beautifully from the air.
• 2014: The light coloured channel running from what is called the Belo Monte dam (but is actually near Fortaleza) runs north and east to the turbines at Belo monte which can be seen just before rejoining the Xingu's natural course.
• 2017: The dam at Fortaleza is diverting much of the water to the new channel and the big bend is in a state of permanent dry season.
• 2016: The white shaded areas show the three negatively impacted zones. The red dot is Altamira, the red bar being the dam across the Xingu itself.

The dam is an ecological disaster. What is written here explains what has gone on, but I always wanted this series of articles to be about the whole river and not its "missing limb". Not for a second should that reduce or excuse this artifical amputation, but much remains and there is much still to explore and understand. We've given the dam enough air time, let's get back to the nature.

It's not just l-numbers: Corys and whiptails
To describe this unique river, I heard the phrase several times on this trip, "It's a river of rivers". Wisdom indeed. Rocks and islands shape the flow of water and there are areas, long sand banks and beaches, where sand accumulates. From dusk and during the night stingrays like to hang out here, but during the day this shallow clear water is home to other things. Indeed, the flow of water over the rocky base of the Xingu river bed throws up all sorts of unusual spots. During the sixth day on the river, we found a beautiful spot where, in the middle of an island which had trees and bushes, was a low waterfall over rocks emptying into a sandy pool with a lot of leaf litter cover. This pool being in the middle of an island with strong current around it, but little current to speak of in the pool. I say pool, it was a good 40m across and roughly circular. Leaf litter is relatively unusual in the Xingu main channel, so we dived in to see what could be found in this sheltered harbour. Even at about two metres deep, the crystal clear water made viewing the bottom of the pool easy. Medium sized Myleus occupied the middle of the water column. I took some video of them and other characins such as Moenkhausia heikoi and some larger Brycon tore around trying to avoid becoming our lunch. My eyes were attracted to movement near the bottom where a pair of really good sized Geophagus (probably G. argyrostictus) were prospecting a long rock perhaps as a good place to start a family. I spent 10 or or 15 minutes hanging at the surface, slowly breathing through my snorkel watching them. Then a branch in the leaf litter moved. It was, I could see now, not a branch but a foot-long whiptail. It's large dark brown blotch and sandy colours making it a perfect match for the brown leaves and sand it had very successfully hidden in plain sight upon.

• The pool within an island within a river
• Living in leaf litter is Loricaria birindelli

Once we starting looking, and our eyes expected to see them, the Xingu whiptail, Loricaria birindellii, were to be found with a few minutes of searching. Only described in 2010, this medium to large sized whiptail is an occasional export from the Rio Xingu and is an attractive and study species that should not be too hard to breed. All Loricaria are lipbooders and as such the male carries and defends the eggs very effectively. You would simply need a well kept aquarium with an above average footprint. Setting up these Loricaria in a 4'x18" or larger aquarium with soft sand, good filtration and some leaf litter (brown, dry beech leaves is a freely available good option) would be an interesting set-up and more or less all they need for breeding. While raising the fry is a challenge in a such an aquarium, there is a lot of surface area in the leaf litter for the fry to find food and Loricaria fry are easier to feed than many other genera of loricariinae (whiptails etc) as they eat what the adults eat from an early stage.

Nearby, only a few kilomteres downstream, we set-up camp on a sandy beach on another of the Xingu's uncountable islands. A small rivulet, no more than six inches deep runs through the beach. It is, literally, teeming with Corydoras. I set-up an underwater camera on a stick dug into the sand and record of lot of video of Corydoras doing what they do in the wild. This reveals that they are actually swimming quite hard in the current despite looking stationary from above. This species of Cory is restricted to the Xingu, it looks a bit like Corydoras cochui from the (relatively) nearby Upper Araguaia River basin in Brazil but, as with many fishes in the Xingu, when you look closely you can see sufficient differences to make this a new species. Described in 2018, Corydoras benattii was previously known as C022, and doesn't appear to be quite as elongated as C. cochui or have a distinct a blotched pattern being more peppered in the darker markings on its side. Straight out of the river it is light yellow with light tan markings. Once in an aquarium for a few days this changes to a paler white base colour with brown to dark grey flecks and blotches of an irregular pattern.

• Fondly nicknamed the "Xingu Hilton", we camped next to a sandy rivulet
• Corydoras benattii, C022, are very hard to see in this habitat

At least for catfish keepers, the most famous species from the Rio Xingu is the zebra pleco, Hypancistrus zebra. Much has been written about the high contrast, highly prized and highly endangered species. Thankfully, it is being bred commercially and by aquarists all over the world. It's future in captivity looks better than its future in the wild as the part of the river Xingu it lives in is rapidly drying out due the contraction of the belo monte mega dam. Keeping and breeding this emblematic fish is well documented, so I'd like more to recount a little on diving for the zebra pleco. Marking the northernmost range of the zebra pleco is a rudimentary signpost; a plank of wood wedged vertically in otherwise nondescript rocks. The water here is deep enough that one has to cling to rocks to avoid being swept away that current while not white-water is strong enough to move you a half a dozen meters in a few seconds. Losing your grip in such a spot means you have to swim very hard to get back to where you were. In this environment, snorkelling to see a fish that is between 1 to 5 metres below the surface is at best inelegant. Here there is almost only granite. It cracks in such a way that huge fissures between a centimetre or three appear right down the otherwise solid rock face. They often run right though the huge boulders in the river. It is in these tight spots that the zebra pleco can be found during the day. My first few attempts at looking into these nooks and crannies were surprisingly successful. I could make out Pseudancistrus asuirini and also Ancistrus ranunculus and either Parancistrus or Spectracanthicus. The next ten or 15 minutes or so were spent in a wonderful battle with the current as I bobbed up and down searching for the black and white pleco holy grail.

One of the fishermen beckoned me over excitedly shouting, "zebra, zebra, aqui!" to a rock about seven metres downstream. In my excitement I quite forgot about the current and arrived with the fisherman rather more quickly than I had anticipated. With effortless skill he caught me and helped me back into a sensible orientation. I dived to look for the pleco but I only could get as deep as the fisherman at the very end of my breath. I did this again and the fisherman gave me his compressed air line so I could breath. I was head down with the fisherman exchanging breaths of air and looking at a zebra pleco. It shone in the gloom. The fisherman left me with the airline and I slowed my breathing, and took some video of the pleco. But there were others in the group and with better photographic equipment than me. So I rose to the surface being careful to exhale compressed air as I rose. Injuring my internal organs even in five metres of water was something I wished to avoid. It was a brief encounter but I was elated to see this fish in nature and understand so much more about it just by fleeting observation. As I gather control of myself I was aware that there was a helicopter in the air above us. It had passed us and was circling an island in the river and returning our way. I heard gunshots from afar. Was the helicopter shooting at us? Many thoughts passed through my head. Were they trying to drive us off? Had we become confused with poachers? We did not know what was going on. It felt prudent to get close to a big rock I could hold on to. Others got near the tethered boat or just watched from wherever they were. The helicopter passed us and more shots were fired. For a few moments this was all slightly tense. Thankfully the helicopter passed us, fired one more shot and headed off. We found out later it was a police helicopter who was shooting at a murderer on the run who had taken refugee on the island. I was glad we hadn't stopped there for lunch.

All of this excitement was soon replaced by the excitement of fishermen catching L082, a pretty and odd loricariid also limited in range like the zebra pleco and therefore highly endangered by the dam too. This is an interesting, species because it more or less fits the bill in terms of belonging to the genus Scobinancistrus, but it is stockier with a smaller adult size and a thick, round in cross section caudal peduncle. It's another animal that has evolved to almost a new genus, clearly undescribed new species, some would argue it is also worthy of its own genus. It's another mostly carnivorous species with large orange tinged light coloured spots on a black background. Recently L082 has been bred in Europe, so some hope exists for this species too.

What predates on zebras? Well, I think they are too small for nature's fishermen, the otters and cormorants and any caiman left (they have been hunted to the point it is unlikely to find one). So it is likely larger fishes, especially Hoplias and Crenicichla that are the main threats and this is why the small plecos (either small species or the young of larger species) have evolved to be flat enough to live in rock crevices during the day and venture forth at night when the majority of predators are sleeping. Indeed, it is the larger pleco species that spawn with hundreds or thousands of eggs that are not found in these nooks and crannies. A typically zebra pleco clutch can be a dozen to fifteen or so eggs, so clearly in nature these fry have a good chance of survival and this must be due to the cave based spawning sites and the protection of these cracks in the rock which are impenetrable to all predators. Hypancistrus zebra may become extinct in the wild in the years ahead. It is unlikely to live in the flooded reservoir upstream of Fortaleza. Maybe small populations will survive in the 100km of river that will have, at best, 20&perc; of the natural water low and probably no season variation. The considerably rarer L173, a deep water species of Hypancistrus from the same area is not likely to have much deep water left to live in. If there is enough water left in the part of the river cut out by the dam, some may survive and let's hope so as that is part of an area for which a large gold-mining deal has been struck, the pessimist in me would bet it'll be bone dry to facilitate the human demand for that precious metal over the coming years.

In the third and final instalment, we're going to look at a few other catfishes from the river as well as the Xingu Royal Pleco, a very pretty Panaqolus species and a mysterious new species of Baryancistrus that does not yet have, and may never get, an l-number of its own.

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