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by Juan Miguel Artigas-Azas |
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This two-part article is based on a recent trip to the Rio Negro and its surrounding varied aquatic habitats made in October 2012 accompanied by a group of knowledgeable aquarists including Ad Konings, Patrick de Rham, Pam Chin, and several others. We started in Manaus, Brazil and traveled primarily via riverboat from the town of Barcelos, 400 kilometers (c. 250 mi) northwest of Manaus. Our three-week adventure took us to many notable sites in both black water and white water habitats where we had the opportunity to observe and photograph the amazing flora and fauna of Amazonia, principally its fishes. What follows is a brief account of my observations of cichlid behavior in the wild from several of these notable locations which will also be continued in the next issue of Cichlid News. Just before landing at Eduardo Gomes International airport at Manaus the excitement grew: this is one of those occasions in life when long time dreams meet reality. It was dark but I could feel the mighty Rio Negro just below us and I was ecstatic. How would it be? For so many years I have had images about the mighty Amazon, the impressive river system and the impregnable tropical rain forest surrounding it. The Amazon was the place where so many of my first aquarium fish came from. Fishes so unique like the glowing cardinal tetra, the majestic angelfish, the bizarre yet so beautiful Arowana, my beloved Oscars, the unlikely and beautiful discus, and so many other fish. After so many years, finally my dream came true. I was there in Manaus, the heart of the Amazon rain forest! In Manaus the expected atmosphere was present: even inside the air-conditioned airport, the heat and incredible humidity of the jungle could already be felt. Driving to the hotel on a beautiful Friday night we witnessed the energy of the city as countless young people packed bars, girls dressed seductive, and music filled the air. Our boat journey into Rio Negro started 400 kilometers (c. 250 mi) northwest of Manaus at the town of Barcelos (0° 58’S, 62° 55’W), a main collecting locality for ornamental tropical fish. The flight over the Rio Negro to get there revealed the magnificence and complexity of the system. More than a river, it is a running lake inside a sea of green, breathtaking to say the least. The two largest archipelagos on earth are found in the Rio Negro and we would see them from the air as well as navigate through them on our way back to Manaus; they are the Mariuá Archipelago with around 600 islands and the incredibly beautiful Anavilhanas with over 400 islands. Incredible mazes of islands and channels, and headaches for sailors. | |
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Navigating the Rio Negro is a unique experience. When you look down, the water is pitch black: no mistake about the name of the river. It is believed that the color of black water rivers is due to humic acid from the released tannins of leaves and wood in the flooded forest of sandy areas. Black water rivers are extremely soft and acidic, with a pH as low as 3.8 and conductivity as low as 10 µS in the Amazonian Rio Negro. Black water rivers have a unique characteristic, for which the Rio Negro is the extreme example: very low concentrations of sodium, magnesium, calcium, and potassium. This fact has very important ecological consequences as many animals need more calcium than is available in black water. So, black waters have a much smaller density of fish than white waters. Water temperature in the Rio Negro was around 30 °C (86 °F). The size of the Rio Negro is astonishing; the main channel was usually over five kilometers (3.1 mi) wide, and 30 km (18.6 mi) at the Anavilhanas and Mariuá archipelagos—that is measured at the end of the dry season! In the rainy season, the river is 30 km (18.6 mi) wide for long stretches, and this goes up to 650 km (404 mi) upstream from Manaus. The gradient of the Rio Negro is very gradual, being just 27 meters (89 ft) above sea level at Manaus, some 1,300 km (808 mi) away from the Atlantic Ocean! The level was 33 meters (108 ft) at Barcelos! This is a gradient of just six meters (19 ft) over 400 km (248 mi) between the two sites. Even so, the flow of the Rio Negro, even in the dry season, is quite fast. I could not see myself swimming against its current. We were navigating at about 10 km (6 mi) an hour against the flow and about 16 km/hr (10 mph) downstream, so falling into the water unseen was a potentially dangerous situation. Our first night aboard was in the middle of the tropical forest where the Demeni and Negro rivers met. One of the nice things about the black water is the almost complete absence of (biting) bugs. The skies were as clear and beautiful as they could be. The sounds of the jungle were all around us; we were surrounded by life, not so hot that you could not sleep, but total peacefulness. | |
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The sand banks near Cumarú (0° 33.558’S, 63° 22.855’W) were like nothing I had seen before. At one side of a small group of islands, the steep walls of a fine white sand bank emerged over a meter (3.3 ft) from the calm surface of the river. The tea-colored water contrasted beautifully against the white sand. The walls were so steep that we could anchor the boat just beside the bank, and be able to jump onto the shore. Cumarú was an exciting place for us, as among the night catch we obtained some beautiful Geophagus winemilleri, G. gottwaldi, and one of my lifetime favorites, the Black Arowana (Osteoglossum ferreirai). Later that night a big storm fell over us forcing us to close every window in the boat. We were then in the middle of a storm that would seem to last for days, but seeing the beautiful morning sky, we wondered if it just had been a dream. | |
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I always had imagined Igarapés (“path of the canoe” in Nheengatu, the local language) as small idyllic, clear water streams inside the jungle. After we reached Igarapé Bariri (0° 19.819’S, 63° 37.978’W) on the left bank of the middle Rio Negro, I was surprised to see the size of it, larger than most of the Mexican rivers I know. We went up for 6 km (3.7 mi) and found a good spot to snorkel (0° 16.727’S, 63° 37.802’W). At this place there was an ornamental fish collecting station, the only construction along the stream. It was one of the most worthwhile localities of the trip. Not just because the Bariri has a breathtaking landscape, but because the fish fauna was overwhelming, including many cichlid species. Dicrossus filamentosus were found in large numbers in the shallow areas, over leaf accumulations or between aquatic vegetation. It turned out to be one of the most common cichlids we encountered in the shallow areas of the Rio Negro. Females and young males were quite conspicuous with their checkerboard color pattern and the few adult males were overwhelmingly beautiful with their bright colors and long filaments. They constantly pick food items from submerged leaves and branches. On a later date, in the Jufari River, we saw a breeding female guiding her fry alone. The bright red color of her pelvic and anal fins made it quite a sight. Mesonauta insignis was particularly abundant in the shallow areas of the flooded forest and small tributaries, moving calmly and majestically, always near the surface. I saw them in small groups on every occasion. We found out that this species is pretty common in the smaller tributaries of the Rio Negro, mostly in areas of very slow or no current. | |
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Heros notatus groups were also common in the Bariri, particularly near entanglements of sunken branches, although I could also see them on open sandy areas, even in a moderate current. They seem quite gregarious and I commonly saw them picking on trunks. We could not see any breeding activity of this cichlid during our visit in October. Some adult specimens would show almost no barring while others showed complete barring. They seemed to have the ability to switch this color pattern in a matter of seconds. I also saw Heros severus in the Bariri, although apparently in smaller numbers than H. notatus, but other than that I could not discern any behavioral difference between the two species which was rather puzzling for me. Of course we know that H. severus is a delayed mouthbrooder, but that we could not observe as there was no breeding activity. I could tell H. severus apart from H. notatus because it has a red ventral area below the lateral line, more intense towards the chest. H. notatus has dark dots scattered through the flanks, with a higher concentration in the anterior part, versus H. severus which just have dots on the cheeks, being less even in this area and smaller in size. | |
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Acaronia nassa is probably the shyest cichlid; it was always close to piles of wood ready to dive in at any sign of threat, but comfortably watching you after it got used to your presence. They have very large eyes, which suggests that they are more active at dawn or dusk. A. nassa moves slowly and I saw them always as single individuals in the company of other cichlid species, although in a given area there were always a good number of them. They were brown in color with a golden cast, the black blotches in the center of the flanks, the humeral zones and the cheek areas were ocellated with light dots. Juveniles have an attractive light blue cast. Adult fish had a very impressive dorsal fin. I thought they were very personable. Hypselecara coryphaenoides was another cichlid I saw normally in mixed, heterospecific groups of other cichlids, mainly Heros spp., but unlike A. nassa, there was always more than one individual in such groups. The red eye on the brown body in adult fish is quite attractive. One of my favorite sightings at Bariri was that of an adult Hoplarchus psittacus, one of my favorite cichlids. He was curious and personable and did not fear me. He would, however, stay in the deeper areas among branch entanglements and while not having scuba gear, it took me a long time before I could finally take a picture of him. I watched this individual picking on the substrate and decaying leaves, as well as on submerged tree branches. | |
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Crenicichla johanna was present in the Bariri and in other places of the middle Rio Negro. This was the largest of the Crenicichla species we saw, probably double the size of C. lenticulata or C. inpa. Those specimens I observed were mostly solitary and often hid among wood entanglements in an ambush position with just the head peeking out. The red eye and the red blotches that form a horizontally dotted line from the humeral zone all the way to the upper part of the caudal peduncle, made it a very attractive sight. Each individual had a strongly-marked black lateral band that runs from the snout to the end of the tail. In dominant individuals the red was also found on the lower flank and even overlaying the black longitudinal band. Young individuals, however, were almost white in the ventral area. This is a very variable fish in terms of coloration and almost each individual was differently marked, particularly those of a different size. Crenicichla lenticulata is a beautiful cichlid species that is found in large groups in the shallow areas, resembling packs of wolves and ignoring small fish that may not deserve the energy necessary to pursue. They were common catches with rod and line using large lures and were good eating too! We were lucky enough to see several breeding pairs of C. lenticulata in the Bariri and in other places. Pairs moved fast and kept their distance from you, and dug deep into wood entanglements as you tried to approach them. One particular pair we saw in the Cachoeireas (falls and rapids) Arará near Manaus had a small pack of “babies” which appeared to me at least 12 cm (4.7 in) in size! | |
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Crenicichla inpa was the least colorful of the Crenicichla species that we saw. They are middle-sized between C. johanna and C. notophthalmus and quite common in the smaller Igarapés. Their main markings were a large black humeral blotch, alternating thin, light-green and black vertical bars extending from the operculum to the beginning of the lower lateral line, and a red ocellated, black blotch on the upper part of the caudal peduncle, just above the lateral line. A black stripe runs the flank from the tip of the snout to the end of the caudal fin. A reddish lachrimal mark was also present. C. inpa was frequently found lying in ambush in the leaf litter or among branches, surprising suitable prey. They would make lightning fast strikes every once in a while. Too fast for me to realize what the prey was! Crenicichla notophthalmus was abundant in the shallow areas and found regularly over leaf litter or aquatic vegetation. They seemed not interested in Apistogramma species or small adult characins, so they likely feed on smaller fish and invertebrates. Females of this species are nicely marked with a red band in the anterior part of the dorsal fin, extending to a round black blotch found in the middle of it. This blotch is surrounded in red, but further back the red band turns into yellow and extends to the end of the fin. The upper part of the dorsal fin is translucent and has a thin red margin. The tail and anal fins are also translucent with a red margin; they also have a red band crossing them in the upper and middle part, respectively. This species has very large eyes, possibly an indication of their preferred feeding time. | |
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One of the surprises for me were my encounters with large groups of Apistogramma gibbiceps in the shallow areas of small igarapés or lakes, both in stagnant and in rather fast flowing water. I knew these fish were harem forming cichlids but I wasn’t ready to see a large density of them, regularly over accumulations of leaves. This little fish exhibits six vertical bars and a horizontal stripe from snout to tail. One of the characteristics of this species is the fact that the lower part of the bar bends obliquely backwards. This little gem was pretty variable in head coloration depending on the population; near Barcelos males have bright golden cheeks with green markings. Apparently, this species waits for the rainy season to spread into the flooded areas of forest to spawn. A cichlid I almost missed in the Bariri is the highly secretive Laetacara thayeri. We nevertheless got to see them often after we discovered their secretive lifestyle. They were always found in small groups in very shallow, marginal areas of streams and lakes, including in tiny creeks or puddles in the forest. Aequidens pallidus was everywhere in the slow flowing areas of the streams and lakes we visited, ranging from shallow to deep areas. This attractively marked cichlasomatine is apparently gregarious although groups are not very large and tend to stay close to some kind of cover. In the Bariri they were found at the edge of large wood entanglements. Small groups of Satanoperca lilith with their beautifully extended dorsal fins moved close over the bottom of slow flow areas, poking regularly with their mouth into the substrate and subsequently filtering the obtained mouthful through their gills. They were hardly intimidated by my presence, but kept a safe distance. | |
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I was able to observe a monstrous Cichla orinocensis among the shallow vegetation. I don’t dare to estimate how large it was, but it certainly was the largest specimen that I saw during the trip and resembled those humongous specimens you see in portraits of proud sport fisherman. Much to my delight this magnificent individual was alive and free. A few times we witnessed what appeared to be feeding frenzies in the shallow water, causing loud water splashes. When we saw the first of these events, we were puzzled by what it was, but we were quickly told “Tucunaré!” which is the native word for Cichla. While underwater, it was interesting to observe large Cichla among a multitude of much smaller fish of several families. The small fish swim around a large Cichla without fear, as apparently the predator just employs its energy in hunting larger prey. Together with Cichla orinocensis we commonly found C. temensis. It was a regular catch with a casting lure and made a delicious meal. Young individuals of both C. orinocensis and C. temensis have horizontal lines of clear dots on the flanks, but large C. orinocensis have three ocellated blotches in the middle part, just where the vertical bars are. In C. temensis these blotches are not ocellated, but it has an irregular black ocellated area on the upper part of the gill plate. The distinction based on color markings puzzled me, as both species seem to have identical life styles and morphology, and I wondered if they differed behaviorally. To be continued ... |
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