(This article was originally published in Cichlid News Magazine, Jan-99 pp. 6-12, It is reproduced here with the permission of author Ron Coleman and Aquatic promotions).
Rio Puerto viejo in Costa Rica, running in the shade of the rain forest where the sunlen logs are critical breeding sites for cichlids. Photos by Ron Coleman.
Just as there are many ways to enjoy keeping cichlids in an aquarium, there are also different ways to experience cichlids in the wild. In previous articles in Cichlid News, authors like Stan Sung, Laif DeMason, and others have described collecting cichlids in Central America. They have visited many fabulous places and collected lots of beautiful fish. In this article, I take a different approach, I will focus on one particular locality, a one kilometer portion of the Rio Puerto Viejo in northeastern Costa Rica and the cichlid fishes found therein.
The geology of Central America ensures that both approaches have merit. The mountain ridge running down the center of Central America has contributed to the profuse speciation that cichlids have undergone in this region. In general, rivers drain either to the east or the west off these mountains. "Parallel" rivers are not interconnected, so each system frequently has had the opportunity over time to evolve its own set of species, cichlids and otherwise. Because each river has a variety of habitats, typically ranging from slow backwaters and log jumbles to fast, rocky stretches, each river is home to a diverse assemblage of cichlids, including smaller, more secretive types, some medium-sized species, and large predatory forms.
To see the maximum diversity of cichlids in a region, you should visit many different drainages. However, to best study how the various species fit together in a single community, spend more time at one location and the picture will slowly reveal itself.
Sometimes the picture that emerges isn't as clear as you might hope for. First, the water often is not particularly clear in Central America. A combination of algae growing in the water and sediment carried from the highlands to the ocean make visibility a challenge in many areas. Algae, by the way, are the only green plants in the river system under consideration here. Lacking other larger plant species, the whole landscape is a rather uninspiring silty-brown. Secondly, some of the fish species present don't exactly draw attention to themselves (if they can help it), but that is part of the real enjoyment of observing cichlids in the wild figuring out what is really going on. Fortunately, the river is relatively benign as tropical rivers go: there are no venomous water snakes (though there are plenty of them on the land), and there are no crocodiles only caimans that max out around six feet or so. I have run into one underwater, at close quarters, and we agreed not to make a fuss about it and went our separate ways.
I have had the good fortune to visit this specific river on four separate occasions, in the summer of 1989 and each March in 1996, 1997, and 1998 as part of my ongoing research into the evolution of cichlid eggs and the parental behaviors involved in their care. Each trip I spend about three weeks snorkelling every day through the same kilometer of water trying to learn more about this community of fishes. Over the past four visits I have uncovered the nesting habits of all but one of the species present. It is a testament to the complexity of the system that I am eager to go back yet again there are still more mysteries to be solved even in this one spot.
There are eight species of cichlids in the Rio Puerto Viejo, namely Archocentrus septemfasciatus, A. nigrofasciatus, Astatheros alfari, A. rostratus, Hypsophrys nicaraguensis, Neetroplus nematopus, Tomocichla tuba, and Parachromis dovii.
The smallest cichlids are Archocentrus septemfasciatus and A. nigrofasciatus (the well-known "convict"). Males of each may reach five inches, but females are often only three or four inches in total length. The convict is so rare that I am always excited to observe them which is hard to believe considering how common it is in the hobby. Its range is more typically to the north and west, but its close relative, A. septemfasciatus, is common in the Puerto Viejo. Brightly colored and quick to breed, there are often dozens of families of A. septemfasciatus to be found near root tangles, branches, and piles of leaves. They nest in small holes in the riverbanks or under logs, sheltered spots in which a little fish can escape the eyes of roving egg-predators.
Cichlids of Rio Puerto Viejo; A female Archocentrus septemfasciatus in courting coloration, then to the right a female Astatheros alfari fanning her eggs laid on top of a sunken log. In the second row there is a typical A. septemfasciatus breeding habitat under the submerged roots of a tree, to the right in the second row the "mouthprints" of an Astatheros rostratus feeding in the area. Third row to the left shows a female A. rostratus guarding her eggs in silty backwater, and to the right a pair of Hypsophrys nicaraguense where the male is normally much larger than the female, they dig caves to place their non-adhesive eggs as can be seen in the picture left in the last row, where to the right you see a breeding pair of Neetroplus nematopus, which show breeding black with a white bar. Photos by Ron Coleman.
Astatheros alfari is not a common fish, and breeding pairs are hard to find. They lay their eggs on the exposed surfaces of submerged logs, but the logs must be in a quiet backwater. Males may be up to nine inches in length, though females are often much smaller (ca. 5"). Parents with their young are quickly recognizable by the bright white and yellow leading edges of the pelvic fins which hang down below the bodies of the parents. The colored fins serve to signal the young and may be the only thing visible in murky water. Danger is signalled by quick flicks of those "flags" which cause the young to move closer to the parents or dive for cover on the bottom.
The next challenge was the ghostly Astatheros rostratus, an uncommon species found in only a few spots in my study area. However, now that I've learned their secret, I'm able to locate them with regularity. As the name suggests, A. rostratus has a pronounced snout and a mouth that functions much like a vacuum. They move along an area of silt, inhaling a "chunk" of the bottom and sifting through it, eating the good stuff (algae and small invertebrates), and spitting out the rest. It was only after watching a large male A. rostratus munch his way across a patch of silt and leaves that something else I had observed suddenly made sense. In shallow silty areas, I had seen huge numbers of small pits, almost as if someone had taken a little cookie cutter and made patterns in the substrate. These I learned are the tell-tale sign that A. rostratus has been feeding here.
The fish itself is beautiful, not in the bold poster coloration of coral reef fishes or Rift Lake cichlids, but in the subtle shimmering blues and whites of its spotted fins, as it meanders through the shadows. I call them "ghost-fish" because they are quick to hide, and by living in silty areas, they are hard to see at the best of times, despite their size. Males are ten inches, females nine inches long. Sometimes all I spy are the two large spots, one in mid-body, the other above and forward, swimming disembodied through the dim waters.
At first I couldn't find this species' nests, but now I know the trick: they "point" to their nests. First I find an individual that seems determined to stay in a specific area in a silty backwater (a sure sign of nesting). If I swim slowly toward the fish, it will move away, but then turn around and face a particular direction. Now you know one line. Swim at it again and it will move off to the side, but once again it will turn and point at the nest. Triangulate the two lines and there will be the nest often a layer of about 1000 small eggs, partially covered in silt, on the surface of a buried log.
Hypsophrys nicaraguense is a fascinating fish. As many aquarists know, "nics" (as they are sometimes called) are the only Central American cichlid to lay non-adhesive eggs. The bright yellow ova often bounce around the bottom of an aquarium. I now know why: H. nicaraguense is a tunnel nester. It was only on my third trip that I finally decoded the signal the nics had been giving all along. On my first two trips, I had been puzzled by the sight of nics hanging out next to a clay bank for no apparent reason. They weren't feeding, and they weren't going anywhere - the two things cichlids do most often in the wild!
On my second trip I noticed that these "layabouts" often seemed to be in characteristic areas, and once I thought I saw one of them dash into a black hole in the bank. I probed with my hand but found nothing. The answer would have to wait another year. I returned the next year armed with high technology: an underwater flashlight. Within minutes it opened up a new world. When I peered inside one of these holes (a tunnel three inches in diameter and 9-10 inches long) there at the back, in a nice little pile, were the bright yellow eggs that aquarists have come to recognize as unique to this species. I had found the missing nest of H. nicaraguense. Within half an hour I had found several more, and the mystery was solved: nics make horizontal tunnels in the clay banks. They are sometimes found in close clusters. I suspect this is because the correct consistency of clay is restricted to particular areas. These areas change from year to year as storms move logs and sand from place to place, exposing or covering the clay. The nests are made by both the male (8-9" long) and the female (6" long).
Black and white Neetroplus nematopus is also a hole-nester, but more of an opportunist. Unlike the neatly-dug holes of the nics, Neetroplus seem to occupy holes dug by others, perhaps shrimps or crabs, or to use hollow logs or cracks in rocks. This species is small, males sometimes getting to six inches, but females only 3-4" in length. I discovered their secret nesting sites when I saw one hovering above the end of a log, fanning into a hollow opening. Fanning, i.e., when a fish moves its pectoral fins back and forth rapidly while keeping the body stationary, functions to drive oxygenated water over eggs. When I saw that fish fanning into the end of that log, I knew there had to be eggs inside, and indeed there were. I have since found many more Neetroplus nests, now that I know where to look. I even found one nesting in a halfburied piece of PVC pipe that had washed down the river.
The most striking fish (and admittedly my favorite) in this community is Tomocichla tuba. It is actually quite common, and I have counted upward of twenty active nests in my study area on a given day. Tomocichla tuba are large fish and easy to spot: males reach fourteen inches in length, while females can be nine inches long. Non-breeding attire in both sexes is a combination of greens, gray, and yellow, but when they breed they are spectacular. Both sexes develop a brilliant white breeding mask that seems to ooze white ink, and a black stripe runs the length of the body from the axil of the pectoral fin to the base of the caudal (an unmistakeable combination). During spawning, the stripe breaks up into vertical black bars, separated by white or yellow. Females may have raspberry red highlights in these lighter areas. Males have pronounced nuchal humps thin and high, rather than bulbous in shape. These are fastwater fish, capable of swimming at phenomenal speeds. They are common because they lay their large eggs in the swiftest portions of the river, unlike any other cichlid. The eggs hatch into large bumble-bee colored fry that can handle incredibly strong currents right from their first day of swimming. It is truly exciting to see a pair of T. tuba with a school of 50-100 fry moving up and down the river in currents so strong that I have to hold onto a log to avoid being swept away.
The last species (and the largest) is the wolf cichlid, Parachromis dovii. They are not common, but they are the top fish predator in this system. In one kilometer, I estimate that there are probably less than a dozen females, and possibly fewer males. The males are "large" (I estimate close to two feet in length). I rarely glimpse a male and when I do, it is usually because we run into each other quite by surprise as I swim around a log. As I choke out the water I've just inhaled, he swims quickly away. Females are big enough at 14" with quite an impressive set of jaws. On half a dozen occasions I have encountered females escorting broods. Interestingly, males are never involved with brood care, unlike all the other cichlids in this community. Fry stay with the female for a long time and may grow to over an inch in length and number several hundred. I have yet to discover where she lays her eggs. There are only a few spots I haven't been able to check to date, such as inside some of the larger hollow logs and in large dark pits at the bases of undercut trees. Maybe next time....
|A breeding pair of Tomocichla tuba guarding their eggs. Photos by Ron Coleman.|